Yong-Ling Ruan

Root-to-shoot signalling: integration of diverse molecules, pathways and functions

Publisher: CSIRO Publishing

Date: 2016

DOI: 10.1071/FP15252

Abstract: Plant adaptive potential is critically dependent upon efficient communication and co-ordination of resource allocation and signalling between above- and below-ground plant parts. Plant roots act as gatekeepers that sense and encode information about soil physical, chemical and biological factors, converting them into a sophisticated network of signals propagated both within the root itself, and also between the root and shoot, to optimise plant performance for a specific set of conditions. In return, plant roots receive and decode reciprocal information coming from the shoot. The communication modes are highly erse and include a broad range of physical (electric and hydraulic signals, propagating Ca2+ and ROS waves), chemical (assimilates, hormones, peptides and nutrients), and molecular (proteins and RNA) signals. Further, different signalling systems operate at very different timescales. It remains unclear whether some of these signalling systems operate in a priming mode(s), whereas others deliver more specific information about the nature of the signal, or whether they carry the same ‘weight’. This review summarises the current knowledge of the above signalling mechanisms, and reveals their hierarchy, and highlights the importance of integration of these signalling components, to enable optimal plant functioning in a dynamic environment.

Uptake and regulation of resource allocation for optimal plant performance and adaptation to stress

Publisher: Frontiers Media SA

Date: 2013

DOI: 10.3389/FPLS.2013.00455

Hexose translocation mediated by SlSWEET5b is required for pollen maturation in Solanum lycopersicum

Publisher: Cold Spring Harbor Laboratory

Date: 31-08-2021

DOI: 10.1101/2021.08.30.458256

Abstract: Pollen fertility is critical for successful fertilization and, accordingly, for crop yield. While sugar unloading affects growth and development of all types of sink organs, the molecular nature for sugar import to tomato pollen is poorly understood. However, SWEET transporters have been proposed to function in pollen development. Here, qRT-PCR revealed that SlSWEET5b was markedly expressed in flowers when compared to the remaining tomato SlSWEET s particularly, in the stamens of maturing flower buds undergoing mitosis. Distinct accumulation of Sl SWEET5b-GUS fusion proteins was present in mature flower buds, especially in anther vascular and inner cells, symplasmic isolated pollen cells and styles. The demonstration that GFP fusion proteins located to the plasma membrane support the idea that the Sl SWEET5b carrier functions in apoplasmic sugar translocation during pollen maturation. Such function is in line with data from yeast complementation experiments and radiotracer uptakes, showing that Sl SWEET5b operates as a low affinity hexose-specific passive facilitator, with a K M of ~36 mM. Most importantly, RNAi-mediated suppression of SlSWEET5b expression resulted in shrunken nucleus-less pollen cells, impaired germination and low seed yield. Interestingly, stamens from SlSWEET5b -silenced tomato mutants contained significantly lower amounts of sucrose and increased invertase activity, pointing to reduced carbon supply and perturbed sucrose homeostasis in this tissue. Taken together, our findings reveal an essential role of Sl SWEET5b in mediating apoplasmic hexose import into phloem unloading cells and into developing pollen cells to support pollen mitosis and maturation in tomato flowers. Plasma-membrane-localized SlSWEET5b facilitates a sequential hexose flux, from phloem to anther cells and from anther locule to pollen, to support pollen maturation and fertility in tomato flowers.

Identification of transcription factors controlling cell wall invertase gene expression for reproductive development via bioinformatic and transgenic analyses

Publisher: Wiley

Date: 04-2021

DOI: 10.1111/TPJ.15218

Abstract: Cell wall invertase (CWIN) hydrolyses sucrose into glucose and fructose in the extracellular matrix and plays crucial roles in assimilate partitioning and sugar signalling. However, the molecular regulators controlling CWIN gene transcription remain unknown. As the first step to address this issue, we performed bioinformatic and transgenic studies, which identified a cohort of transcription factors (TFs) modulating CWIN gene expression in Arabidopsis thaliana . Comprehensive bioinformatic analyses identified 18 TFs as putative regulators of the expression of AtCWIN2 and AtCWIN4 that are predominantly expressed in Arabidopsis reproductive organs. Among them, MYB21, ARF6, ARF8, AP3 and CRC were subsequently shown to be the most likely regulators of CWIN gene expression based on molecular characterization of the respective mutant of each candidate TF. More specifically, the obtained data indicate that ARF6, ARF8 and MYB21 regulate CWIN2 expression in the anthers and CWIN4 in nectaries, anthers and petals, whereas AP3 and CRC were determined primarily to regulate the transcriptional activity of CWIN4 . TF‐promoter interaction assays demonstrated that ARF6 and ARF8 directly control CWIN2 and CWIN4 transcription with AP3 activating CWIN4 . The involvement of ARF8 in regulating CWIN4 expression was further supported by the finding that enhanced CWIN4 expression partially recovered the short silique phenotype displayed by the arf8‐3 mutant. The identification of the five TFs regulating CWIN expression serves as a launching pad for future studies to dissect the upstream molecular network underpinning the transcription of CWINs and provides a new avenue, potentially, to engineer assimilate allocation and reproductive development for improving seed yield.

Unraveling mechanisms of cell expansion linking solute transport, metabolism, plasmodesmtal gating and cell wall dynamics

Publisher: Informa UK Limited

Date: 12-2010

DOI: 10.4161/PSB.5.12.13568

Wheat photosystem II heat tolerance responds dynamically to short- and long-term warming

Publisher: Oxford University Press (OUP)

Date: 23-05-2022

DOI: 10.1093/JXB/ERAC039

Abstract: Wheat photosynthetic heat tolerance can be characterized using minimal chlorophyll fluorescence to quantify the critical temperature (Tcrit) above which incipient damage to the photosynthetic machinery occurs. We investigated intraspecies variation and plasticity of wheat Tcrit under elevated temperature in field and controlled-environment experiments, and assessed whether intraspecies variation mirrored interspecific patterns of global heat tolerance. In the field, wheat Tcrit varied diurnally—declining from noon through to sunrise—and increased with phenological development. Under controlled conditions, heat stress (36 °C) drove a rapid (within 2 h) rise in Tcrit that peaked after 3–4 d. The peak in Tcrit indicated an upper limit to PSII heat tolerance. A global dataset [comprising 183 Triticum and wild wheat (Aegilops) species] generated from the current study and a systematic literature review showed that wheat leaf Tcrit varied by up to 20 °C (roughly two-thirds of reported global plant interspecies variation). However, unlike global patterns of interspecies Tcrit variation that have been linked to latitude of genotype origin, intraspecific variation in wheat Tcrit was unrelated to that. Overall, the observed genotypic variation and plasticity of wheat Tcrit suggest that this trait could be useful in high-throughput phenotyping of wheat photosynthetic heat tolerance.

Wheat photosystem II heat tolerance responds dynamically to short and long-term warming

Publisher: Cold Spring Harbor Laboratory

Date: 04-11-2021

DOI: 10.1101/2021.11.01.466822

Abstract: Heat-induced inhibition of photosynthesis is a key factor in declining wheat performance and yield. Variation in wheat heat tolerance can be characterised using the critical temperature ( T crit ) above which incipient damage to the photosynthetic machinery occurs. We investigated intraspecies variation and plasticity of wheat T crit under elevated temperature in field and controlled environment experiments. We also assessed whether intraspecies variation in wheat T crit mirrors patterns of global interspecies variation in heat tolerance reported for mostly wild, woody plants. In the field, wheat T crit varied through the course of a day, peaking at noon and lowest at sunrise, and increased as plants developed from heading to anthesis and grain filling. Under controlled temperature conditions, heat stress (36°C) was associated with a rapid rise in wheat T crit (i.e. within two hours of heat stress) that peaked after 3–4 days. These peaks in T crit indicate a physiological limitation to photosystem II heat tolerance. Analysis of a global dataset (comprising 183 Triticum and wild wheat ( Aegilops ) species) generated from the current study and a systematic literature review showed that wheat leaf T crit varied by up to 20°C (about two-thirds of reported global plant interspecies variation). However, unlike global patterns of interspecies T crit variation which has been linked to latitude of genotype origin, intraspecific variation in wheat T crit was unrelated to that. Yet, the observed genotypic variation and plasticity of wheat T crit suggests that this trait could be a useful tool for high-throughput phenotyping of wheat photosynthetic heat tolerance.

Wheat photosystem II heat tolerance: evidence for genotype‐by‐environment interactions

Publisher: Wiley

Date: 26-07-2022

DOI: 10.1111/TPJ.15894

Abstract: High temperature stress inhibits photosynthesis and threatens wheat production. One measure of photosynthetic heat tolerance is T crit – the critical temperature at which incipient damage to photosystem II (PSII) occurs. This trait could be improved in wheat by exploiting genetic variation and genotype‐by‐environment interactions (GEI). Flag leaf T crit of 54 wheat genotypes was evaluated in 12 thermal environments over 3 years in Australia, and analysed using linear mixed models to assess GEI effects. Nine of the 12 environments had significant genetic effects and highly variable broad‐sense heritability ( H 2 ranged from 0.15 to 0.75). T crit GEI was variable, with 55.6% of the genetic variance across environments accounted for by the factor analytic model. Mean daily growth temperature in the month preceding anthesis was the most influential environmental driver of T crit GEI, suggesting biochemical, physiological and structural adjustments to temperature requiring different durations to manifest. These changes help protect or repair PSII upon exposure to heat stress, and may improve carbon assimilation under high temperature. To support breeding efforts to improve wheat performance under high temperature, we identified genotypes superior to commercial cultivars commonly grown by farmers, and demonstrated potential for developing genotypes with greater photosynthetic heat tolerance.

Suppression of sucrose synthase gene expression represses cotton fiber cell initiation, elongation, and seed development

Publisher: Oxford University Press (OUP)

Date: 13-03-2003

DOI: 10.1105/TPC.010108

Abstract: Cotton is the most important textile crop as a result of its long cellulose-enriched mature fibers. These single-celled hairs initiate at anthesis from the ovule epidermis. To date, genes proven to be critical for fiber development have not been identified. Here, we examined the role of the sucrose synthase gene (Sus) in cotton fiber and seed by transforming cotton with Sus suppression constructs. We focused our analysis on 0 to 3 days after anthesis (DAA) for early fiber development and 25 DAA, when the fiber and seed are maximal in size. Suppression of Sus activity by 70% or more in the ovule epidermis led to a fiberless phenotype. The fiber initials in those ovules were fewer and shrunken or collapsed. The level of Sus suppression correlated strongly with the degree of inhibition of fiber initiation and elongation, probably as a result of the reduction of hexoses. By 25 DAA, a portion of the seeds in the fruit showed Sus suppression only in the seed coat fibers and transfer cells but not in the endosperm and embryo. These transgenic seeds were identical to wild-type seeds except for much reduced fiber growth. However, the remaining seeds in the fruit showed Sus suppression both in the seed coat and in the endosperm and embryo. These seeds were shrunken with loss of the transfer cells and were <5% of wild-type seed weight. These results demonstrate that Sus plays a rate-limiting role in the initiation and elongation of the single-celled fibers. These analyses also show that suppression of Sus only in the maternal seed tissue represses fiber development without affecting embryo development and seed size. Additional suppression in the endosperm and embryo inhibits their own development, which blocks the formation of adjacent seed coat transfer cells and arrests seed development entirely.

A Novel Isoform of Sucrose Synthase Is Targeted to the Cell Wall during Secondary Cell Wall Synthesis in Cotton Fiber

Publisher: Oxford University Press (OUP)

Date: 14-07-2011

DOI: 10.1104/PP.111.178574

Abstract: Sucrose (Suc) synthase (Sus) is the major enzyme of Suc breakdown for cellulose biosynthesis in cotton (Gossypium hirsutum) fiber, an important source of fiber for the textile industry. This study examines the tissue-specific expression, relative abundance, and temporal expression of various Sus transcripts and proteins present in cotton. A novel isoform of Sus (SusC) is identified that is expressed at high levels during secondary cell wall synthesis in fiber and is present in the cell wall fraction. The phylogenetic relationships of the deduced amino acid sequences indicate two ancestral groups of Sus proteins predating the ergence of monocots and dicots and that SusC sequences form a distinct branch in the phylogeny within the dicot-specific clade. The subcellular location of the Sus isoforms is determined, and it is proposed that cell wall-localized SusC may provide UDP-glucose for cellulose and callose synthesis from extracellular sugars.

Delayed pollination and low availability of assimilates are major factors causing maize kernel abortion

Publisher: Oxford University Press (OUP)

Date: 09-02-2018

DOI: 10.1093/JXB/ERY013

Evolution of cytosolic and organellar invertases empowered the colonization and thriving of land plants

Publisher: Oxford University Press (OUP)

Date: 11-07-2023

DOI: 10.1093/PLPHYS/KIAD401

Abstract: The molecular innovation underpinning efficient carbon and energy metabolism during evolution of land plants remains largely unknown. Invertase-mediated sucrose cleavage into hexoses is central to fuel growth. Why some cytoplasmic invertases (CINs) function in the cytosol, whereas others operate in chloroplasts and mitochondria, is puzzling. We attempted to shed light on this question from an evolutionary perspective. Our analyses indicated that plant CINs originated from a putatively orthologous ancestral gene in cyanobacteria and formed the plastidic CIN (α1 clade) through endosymbiotic gene transfer, while its duplication in algae with a loss of its signal peptide produced the β clade CINs in the cytosol. The mitochondrial CINs (α2) were derived from duplication of the plastidic CINs and coevolved with vascular plants. Importantly, the copy number of mitochondrial and plastidic CINs increased upon the emergence of seed plants, corresponding with the rise of respiratory, photosynthetic, and growth rates. The cytosolic CIN (β subfamily) kept expanding from algae to gymnosperm, indicating its role in supporting the increase in carbon use efficiency during evolution. Affinity purification mass spectrometry identified a cohort of proteins interacting with α1 and 2 CINs, which points to their roles in plastid and mitochondrial glycolysis, oxidative stress tolerance, and the maintenance of subcellular sugar homeostasis. Collectively, the findings indicate evolutionary roles of α1 and α2 CINs in chloroplasts and mitochondria for achieving high photosynthetic and respiratory rates, respectively, which, together with the expanding of cytosolic CINs, likely underpin the colonization of land plants through fueling rapid growth and biomass production.

Preventive detention of terrorists

Publisher: Edward Elgar Publishing

Date: 27-07-2021

DOI: 10.4337/9781800373075.00014

Hexose translocation mediated by SlSWEET5b is required for pollen maturation in Solanum lycopersicum

Publisher: Oxford University Press (OUP)

Date: 15-02-2022

DOI: 10.1093/PLPHYS/KIAC057

Abstract: Pollen fertility is critical for successful fertilization and, accordingly, for crop yield. While sugar unloading affects the growth and development of all types of sink organs, the molecular nature of sugar import to tomato (Solanum lycopersicum) pollen is poorly understood. However, sugar will eventually be exported transporters (SWEETs) have been proposed to be involved in pollen development. Here, reverse transcription-quantitative polymerase chain reaction (PCR) revealed that SlSWEET5b was markedly expressed in flowers when compared to the remaining tomato SlSWEETs, particularly in the stamens of maturing flower buds undergoing mitosis. Distinct accumulation of SlSWEET5b-β-glucuronidase activities was present in mature flower buds, especially in anther vascular and inner cells, symplasmic isolated microspores (pollen grains), and styles. The demonstration that SlSWEET5b-GFP fusion proteins are located in the plasma membrane supports the idea that the SlSWEET5b carrier functions in apoplasmic sugar translocation during pollen maturation. This is consistent with data from yeast complementation experiments and radiotracer uptake, showing that SlSWEET5b operates as a low-affinity hexose-specific passive facilitator, with a Km of ∼36 mM. Most importantly, RNAi-mediated suppression of SlSWEET5b expression resulted in shrunken nucleus-less pollen cells, impaired germination, and low seed yield. Moreover, stamens from SlSWEET5b-silenced tomato mutants showed significantly lower amounts of sucrose (Suc) and increased invertase activity, indicating reduced carbon supply and perturbed Suc homeostasis in these tissues. Taken together, our findings reveal the essential role of SlSWEET5b in mediating apoplasmic hexose import into phloem unloading cells and into developing pollen cells to support pollen mitosis and maturation in tomato flowers.

Cell Wall Invertase and Sugar Transporters Are Differentially Activated in Tomato Styles and Ovaries During Pollination and Fertilization

Publisher: Frontiers Media SA

Date: 18-04-2019

DOI: 10.3389/FPLS.2019.00506

The delayed initiation and slow elongation of fuzz-like short fibre cells in relation to altered patterns of sucrose synthase expression and plasmodesmata gating in a lintless mutant of cotton

Publisher: Oxford University Press (OUP)

Date: 24-01-2005

DOI: 10.1093/JXB/ERI091

Abstract: Cotton (Gossypium hirsutum L.) seed develops single-celled long fibres (lint) from the seed-coat epidermis at anthesis. Previous studies have shown that the initiation and rapid elongation of these fibres requires the expression of sucrose synthase (Sus) and, potentially, a transient closure of plasmodesmata. This study extends the previous work to examine the patterns of Sus expression and plasmodesmata gating in fuzz-like short fibres of a mutant that shows delayed initiation and much slower and reduced elongation of the fibre cells. Immunolocalization studies revealed delayed expression of Sus in the mutant seed-coat epidermis that correlates temporally and spatially with the initiation of the fibre cells. Anatomically, these short fibres differed from the normal lint in that their basal ends enlarged immediately after initiation, while the majority of the normal lint on wild-type seed did not show this enlargement until the end of elongation. Suppression of Sus expression in the seed-coat epidermis of the transgenic plants reduced the length of both lint and short fuzz fibres at maturity, suggesting that the growth of short fibres also requires high levels of Sus expression. Confocal imaging of the membrane-impermeant fluorescent solute carboxyfluorescein (CF) revealed no closure of plasmodesmata during the entire elongation period of short fibres from the mutant seed. These results show (i) the delayed initiation of fuzz-like short fibres from the mutant seed correlates with delayed or insufficient expression of Sus in a subset of seed-coat epidermal cells destined to become fibres and (ii) the much shortened elongation of the fibres from the mutant may be related to their inability to close plasmodesmata.

Localization of sucrose synthase in developing seed and siliques of Arabidopsis thaliana reveals diverse roles for SUS during development

Publisher: Oxford University Press (OUP)

Date: 04-07-2008

DOI: 10.1093/JXB/ERN180

Looking into ‘hair tonics’ for cotton fiber initiation

Publisher: Wiley

Date: 24-09-2020

DOI: 10.1111/NPH.16898

Regulation of cell division and expansion by sugar and auxin signaling

Publisher: Frontiers Media SA

Date: 2013

DOI: 10.3389/FPLS.2013.00163

Molecular Evolution of Grass Stomata

Publisher: Elsevier BV

Date: 02-2017

DOI: 10.1016/J.TPLANTS.2016.09.005

Abstract: Grasses began to ersify in the late Cretaceous Period and now dominate more than one third of global land area, including three-quarters of agricultural land. We hypothesize that their success is likely attributed to the evolution of highly responsive stomata capable of maximizing productivity in rapidly changing environments. Grass stomata harness the active turgor control mechanisms present in stomata of more ancient plant lineages, maximizing several morphological and developmental features to ensure rapid responses to environmental inputs. The evolutionary development of grass stomata appears to have been a gradual progression. Therefore, understanding the complex structures, developmental events, regulatory networks, and combinations of ion transporters necessary to drive rapid stomatal movement may inform future efforts towards breeding new crop varieties.

Shoot–root carbon allocation, sugar signalling and their coupling with nitrogen uptake and assimilation

Publisher: CSIRO Publishing

Date: 2016

DOI: 10.1071/FP15249

Abstract: Roots and shoots are distantly located but functionally interdependent. The growth and development of these two organ systems compete for energy and nutrient resource, and yet, they keep a dynamic balance with each other for growth and development. The success of such a relationship depends on efficient root-shoot communication. Aside from the well-known signalling processes mediated by hormones such as auxin and cytokinin, sugars have recently been shown to act as a rapid signal to co-ordinate root and shoot development in response to endogenous and exogenous clues, in parallel to their function as carbon and energy resources for biomass production. New findings from studies on vascular fluids have provided molecular insights into the role of sugars in long-distance communications between shoot and root. In this review, we discussed phloem- and xylem- translocation of sugars and the impacts of sugar allocation and signalling on balancing root–shoot development. Also, we have taken the shoot–root carbon–nitrogen allocation as an ex le to illustrate the communication between the two organs through multi-layer root–shoot–root signalling circuits, comprising sugar, nitrogen, cytokinin, auxin and vascular small peptide signals.

Overexpression of a Potato Sucrose Synthase Gene in Cotton Accelerates Leaf Expansion, Reduces Seed Abortion, and Enhances Fiber Production

Publisher: Elsevier BV

Date: 03-2012

DOI: 10.1093/MP/SSR090

Abstract: Sucrose synthase (Sus) is a key enzyme in the breakdown of sucrose and is considered a biochemical marker for sink strength, especially in crop species, based on mutational and gene suppression studies. It remains elusive, however, whether, or to what extent, increase in Sus activity may enhance sink development. We aimed to address this question by expressing a potato Sus gene in cotton where Sus expression has been previously shown to be critical for normal seed and fiber development. Segregation analyses at T1 generation followed by studies in homozygous progeny lines revealed that increased Sus activity in cotton (1) enhanced leaf expansion with the effect evident from young leaves emerging from shoot apex (2) improved early seed development, which reduced seed abortion, hence enhanced seed set, and (3) promoted fiber elongation. In young leaves of Sus overexpressing lines, fructose concentrations were significantly increased whereas, in elongating fibers, both fructose and glucose levels were increased. Since hexoses contribute little to osmolality in leaves, in contrast to developing fibers, it is concluded that high Sus activity promotes leaf development independently of osmotic regulation, probably through sugar signaling. The analyses also showed that doubling the Sus activity in 0-d cotton seeds increased their fresh weight by about 30%. However, further increase in Sus activity did not lead to any further increase in seed weight, indicating an upper limit for the Sus overexpression effect. Finally, based on the observed additive effect on fiber yield from increased fiber length and seed number, a new strategy is proposed to increase cotton fiber yield by improving seed development as a whole, rather than solely focusing on manipulating fiber growth.

Winners take all: competition for carbon resource determines grain fate

Publisher: Elsevier BV

Date: 08-2023

DOI: 10.1016/J.TPLANTS.2023.03.015

New Insights into Roles of Cell Wall Invertase in Early Seed Development Revealed by Comprehensive Spatial and Temporal Expression Patterns of GhCWIN1 in Cotton    

Publisher: Oxford University Press (OUP)

Date: 03-08-2012

DOI: 10.1104/PP.112.203893

Abstract: Despite substantial evidence on the essential roles of cell wall invertase (CWIN) in seed filling, it remains largely unknown how CWIN exerts its regulation early in seed development, a critical stage that sets yield potential. To fill this knowledge gap, we systematically examined the spatial and temporal expression patterns of a major CWIN gene, GhCWIN1, in cotton (Gossypium hirsutum) seeds from prefertilization to prestorage phase. GhCWIN1 messenger RNA was abundant at the innermost seed coat cell layer at 5 d after anthesis but became undetectable at 10 d after anthesis, at the onset of its differentiation into transfer cells characterized by wall ingrowths, suggesting that CWIN may negatively regulate transfer cell differentiation. Within the filial tissues, GhCWIN1 transcript was detected in endosperm cells undergoing nuclear ision but not in those cells at the cellularization stage, with similar results observed in Arabidopsis (Arabidopsis thaliana) endosperm for CWIN, AtCWIN4. These findings indicate a function of CWIN in nuclear ision but not cell wall biosynthesis in endosperm, contrasting to the role proposed for sucrose synthase (Sus). Further analyses revealed a preferential expression pattern of GhCWIN1 and AtCWIN4 in the provascular region of the torpedo embryos in cotton and Arabidopsis seed, respectively, indicating a role of CWIN in vascular initiation. Together, these novel findings provide insights into the roles of CWIN in regulating early seed development spatially and temporally. By comparing with previous studies on Sus expression and in conjunction with the expression of other related genes, we propose models of CWIN- and Sus-mediated regulation of early seed development.

Pathway and control of sucrose import into initiating cotton fibre cells

Publisher: CSIRO Publishing

Date: 2000

DOI: 10.1071/PP99154

Abstract: This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999 Our aim is to unravel the mechanisms controlling fibre cell initiation from the epidermis of cotton (Gossypium hirsutum L.) ovules. We compared the development of fibres and trichomes in wild type cotton and a fibreless seed (fls) mutant, and determined the cellular pathway of sucrose transport into fibre initials on the day of anthesis. Although fibre initiation is inhibited in the fls mutant, leading to the fibreless phenotype, trichome development in other parts of the plant is normal. Confocal imaging analysis revealed that the fluorescent molecule, 5(6)-carboxyfluorescein, which is transported symplastically, moved readily from the integument phloem into initiating fibres. Plasmolysis studies showed that the fibre initials and adjacent non-initiating ovule epidermal cells have similar osmotic potential. Immunolocalisation analysis showed the absence of sucrose transporter proteins in the initiating fibre, but their abundance in the transfer cell precursors at the innermost integument. These results (i) demonstrate that fibre cell initiation is controlled by unique mechanism(s) that differ from that for normal trichome development (ii) show a symplastic pathway of sucrose import into initiating fibres and strengthen the current opinion that sucrose synthase is likely to be the key enzyme mobilising sucrose into initiating fibres and (iii) suggest that the initial protrusion of the fibre cells above the ovule surface is largely achieved by increased cell wall extensibility rather than higher turgor as is commonly thought.

Acclimation of leaf photosynthesis and respiration to warming in field‐grown wheat

Publisher: Wiley

Date: 11-01-2021

DOI: 10.1111/PCE.13971

Abstract: Climate change and future warming will significantly affect crop yield. The capacity of crops to dynamically adjust physiological processes (i.e., acclimate) to warming might improve overall performance. Understanding and quantifying the degree of acclimation in field crops could ensure better parameterization of crop and Earth System models and predictions of crop performance. We hypothesized that for field‐grown wheat, when measured at a common temperature (25°C), crops grown under warmer conditions would exhibit acclimation, leading to enhanced crop performance and yield. Acclimation was defined as (a) decreased rates of net photosynthesis at 25°C ( A 25 ) coupled with lower maximum carboxylation capacity ( V cmax 25 ), (b) reduced leaf dark respiration at 25°C (both in terms of O 2 consumption R dark _O 2 25 and CO 2 efflux R dark _CO 2 25 ) and (c) lower R dark _CO 2 25 to V cmax 25 ratio. Field experiments were conducted over two seasons with 20 wheat genotypes, sown at three different planting dates, to test these hypotheses. Leaf‐level CO 2 ‐based traits ( A 25 , R dark _CO 2 25 and V cmax 25 ) did not show the classic acclimation responses that we hypothesized by contrast, the hypothesized changes in R dark_ O 2 were observed. These findings have implications for predictive crop models that assume similar temperature response among these physiological processes and for predictions of crop performance in a future warmer world.

Silencing the vacuolar invertase geneGhVIN1blocks cotton fiber initiation from the ovule epidermis, probably by suppressing a cohort of regulatory genes via sugar signaling

Publisher: Wiley

Date: 29-04-2014

DOI: 10.1111/TPJ.12512

Abstract: Cotton fibers, the most important source of cellulose for the global textile industry, are single-celled trichomes derived from the ovule epidermis at or just prior to anthesis. Despite progress in understanding cotton fiber elongation and cell-wall biosynthesis, knowledge regarding the molecular basis of fiber cell initiation, the first step of fiber development determining the fiber yield potential, remains elusive. Here, we provide evidence that expression of a vacuolar invertase (VIN) is an early event that is essential for cotton fiber initiation. RNAi-mediated suppression of GhVIN1, a major VIN gene that is highly expressed in wild-type fiber initials, resulted in significant reduction of VIN activity and consequently a fiberless seed phenotype in a dosage dependent manner. The absence of a negative effect on seed development in these fiberless seeds indicates that the phenotype is unlikely to be due to lack of carbon nutrient. Gene expression analyses coupled with in vitro ovule culture experiments revealed that GhVIN1-derived hexose signaling may play an indispensable role in cotton fiber initiation, probably by regulating the transcription of several MYB transcription factors and auxin signaling components that were previously identified as required for fiber initiation. Together, the data represent a significant advance in understanding the mechanisms of cotton fiber initiation, and provide the first indication that VIN-mediated hexose signaling may act as an early event modulating the expression of regulatory genes and hence cell differentiation from the ovule epidermis.

Developmental and molecular physiological evidence for the role of phosphoenolpyruvate carboxylase in rapid cotton fibre elongation

Publisher: Oxford University Press (OUP)

Date: 08-10-2009

DOI: 10.1093/JXB/ERP299

Wheat respiratory O2 consumption falls with night warming alongside greater respiratory CO2 loss and reduced biomass

Publisher: Oxford University Press (OUP)

Date: 15-10-2021

DOI: 10.1093/JXB/ERAB454

Abstract: Warming nights are correlated with declining wheat growth and yield. As a key determinant of plant biomass, respiration consumes O2 as it produces ATP and releases CO2 and is typically reduced under warming to maintain metabolic efficiency. We compared the response of respiratory O2 and CO2 flux to multiple night and day warming treatments in wheat leaves and roots, using one commercial (Mace) and one breeding cultivar grown in controlled environments. We also examined the effect of night warming and a day heatwave on the capacity of the ATP-uncoupled alternative oxidase (AOX) pathway. Under warm nights, plant biomass fell, respiratory CO2 release measured at a common temperature was unchanged (indicating higher rates of CO2 release at prevailing growth temperature), respiratory O2 consumption at a common temperature declined, and AOX pathway capacity increased. The uncoupling of CO2 and O2 exchange and enhanced AOX pathway capacity suggest a reduction in plant energy demand under warm nights (lower O2 consumption), alongside higher rates of CO2 release under prevailing growth temperature (due to a lack of down-regulation of respiratory CO2 release). Less efficient ATP synthesis, teamed with sustained CO2 flux, could thus be driving observed biomass declines under warm nights.

A transcriptional landscape underlying sugar import for grain set in maize.

Publisher: Wiley

Date: 25-02-2022

DOI: 10.1111/TPJ.15668

Abstract: Developing seed depends on sugar supply for its growth and yield formation. Maize (Zea mays L.) produces the largest grains among cereals. However, there is a lack of holistic understanding of the transcriptional landscape of genes controlling sucrose transport to, and utilization within, maize grains. By performing in-depth data mining of spatio-temporal transcriptomes coupled with histological and heterologous functional analyses, we identified transporter genes specifically expressed in the maternal-filial interface, including (i) ZmSWEET11/13b in the placento-chalazal zone, where sucrose is exported into the apoplasmic space, and (ii) ZmSTP3, ZmSWEET3a/4c (monosaccharide transporters), ZmSUT1, and ZmSWEET11/13a (sucrose transporters) in the basal endosperm transfer cells for retrieval of apoplasmic sucrose or hexoses after hydrolysis by extracellular invertase. In the embryo and its surrounding regions, an embryo-localized ZmSUT4 and a cohort of ZmSWEETs were specifically expressed. Interestingly, drought repressed those ZmSWEETs likely exporting sucrose but enhanced the expression of most transporter genes for uptake of apoplasmic sugars. Importantly, this drought-induced fluctuation in gene expression was largely attenuated by an increased C supply via controlled pollination, indicating that the altered gene expression is conditioned by C availability. Based on the analyses above, we proposed a holistic model on the spatio-temporal expression of genes that likely govern sugar transport and utilization across maize maternal and endosperm and embryo tissues during the critical stage of grain set. Collectively, the findings represent an advancement towards a holistic understanding of the transcriptional landscape underlying post-phloem sugar transport in maize grain and indicate that the drought-induced changes in gene expression are attributable to low C status.

Critical Roles of Vacuolar Invertase in Floral Organ Development and Male and Female Fertilities Are Revealed through Characterization of GhVIN1-RNAi Cotton Plants

Publisher: Oxford University Press (OUP)

Date: 11-03-2016

DOI: 10.1104/PP.16.00197

Transcriptomic and metabolomics responses to elevated cell wall invertase activity during tomato fruit set

Publisher: Oxford University Press (OUP)

Date: 10-07-2017

DOI: 10.1093/JXB/ERX219

Expression of sucrose synthase in the developing endosperm is essential for early seed development in cotton

Publisher: CSIRO Publishing

Date: 2008

DOI: 10.1071/FP08017

Abstract: Successful seed development requires coordinated interaction of the endosperm and embryo. In most dicotyledonous seeds, the endosperm is crushed and absorbed by the expanding embryo in the later stages of seed development. Little is known about the metabolic interaction between the two filial tissues early in seed development. We examined the potential role of sucrose synthase (Sus) in the endosperm development of cotton. Sus was immunologically localised in the cellularising endosperm, but not in the heart-stage embryo at 10 days after anthesis. The activities of Sus and acid invertase were significantly higher in the endosperm than in the young embryos, which corresponded to a steep concentration difference in hexoses between the endosperm and the embryo. This observation indicates a role for the endosperm in generating hexoses for the development of the two filial tissues. Interestingly, Sus expression and starch deposition were spatially separated in the seeds. Silencing the expression of Sus in the endosperm using an RNAi approach led to the arrest of early seed development. Histochemical analyses revealed a significant reduction in cellulose and callose in the deformed endosperm cells of the Sus-suppressed seed. The data indicate a critical role of Sus in early seed development through regulation of endosperm formation.

Live Long and Prosper: Roles of Sugar and Sugar Polymers in Seed Vigor

Publisher: Elsevier BV

Date: 2018

DOI: 10.1016/J.MOLP.2017.12.012

Understanding and manipulating sucrose phloem loading, unloading, metabolism, and signalling to enhance crop yield and food security

Publisher: Oxford University Press (OUP)

Date: 17-12-2013

DOI: 10.1093/JXB/ERT416

Abstract: Sucrose is produced in, and translocated from, photosynthetically active leaves (sources) to support non-photosynthetic tissues (sinks), such as developing seeds, fruits, and tubers. Different plants can utilize distinct mechanisms to transport sucrose into the phloem sieve tubes in source leaves. While phloem loading mechanisms have been extensively studied in dicot plants, there is less information about phloem loading in monocots. Maize and rice are major dietary staples, which have previously been proposed to use different cellular routes to transport sucrose from photosynthetic cells into the translocation stream. The anatomical, physiological, and genetic evidence supporting these conflicting hypotheses is examined. Upon entering sink cells, sucrose often is degraded into hexoses for a wide range of metabolic and storage processes, including biosynthesis of starch, protein, and cellulose, which are all major constituents for food, fibre, and fuel. Sucrose, glucose, fructose, and their derivate, trehalose-6-phosphate, also serve as signalling molecules to regulate gene expression either directly or through cross-talk with other signalling pathways. As such, sugar transport and metabolism play pivotal roles in plant development and realization of crop yield that needs to be increased substantially to meet the projected population demand in the foreseeable future. This review will discuss the current understanding of the control of carbon partitioning from the cellular to whole-plant levels, focusing on (i) the pathways employed for phloem loading in source leaves, particularly in grasses, and the routes used in sink organs for phloem unloading (ii) the transporter proteins responsible for sugar efflux and influx across plasma membranes and (iii) the key enzymes regulating sucrose metabolism, signalling, and utilization. Ex les of how sugar transport and metabolism can be manipulated to improve crop productivity and stress tolerance are discussed.

Genotypic and developmental evidence for the role of plasmodesmatal regulation in cotton fiber elongation mediated by callose turnover

Publisher: Oxford University Press (OUP)

Date: 12-2004

DOI: 10.1104/PP.104.051540

Abstract: Cotton fibers are single-celled hairs that elongate to several centimeters long from the seed coat epidermis of the tetraploid species (Gossypium hirsutum and Gossypium barbadense). Thus, cotton fiber is a unique system to study the mechanisms of rapid cell expansion. Previous work has shown a transient closure of plasmodesmata during fiber elongation (Y.-L. Ruan, D.J. Llewellyn, R.T. Furbank [2001] Plant Cell 13: 47–60). To examine the importance of this closure in fiber elongation, we compared the duration of the plasmodesmata closure among different cotton genotypes differing in fiber length. Confocal imaging of the membrane-impermeant fluorescent molecule carboxyfluorescein revealed a genotypic difference in the duration of the plasmodesmata closure that positively correlates with fiber length among three tetraploid genotypes and two diploid progenitors. In all cases, the closure occurred at the rapid phase of elongation. Aniline blue staining and immunolocalization studies showed that callose deposition and degradation at the fiber base correlates with the timing of plasmodesmata closure and reopening, respectively. Northern analyses showed that the expression of a fiber-specific β-1,3-glucanase gene, GhGluc1, was undetectable when callose was deposited at the fiber base but became evident at the time of callose degradation. Genotypically, the level of GhGluc1 expression was high in the short fiber genotype and weak in the intermediate and long fiber genotypes. The data provide genotypic and developmental evidence that (1) plasmodesmata closure appears to play an important role in elongating cotton fibers, (2) callose deposition and degradation may be involved in the plasmodesmata closure and reopening, respectively, and (3) the expression of GhGluc1 could play a role in this process by degrading callose, thus opening the plasmodesmata.

Cell Wall Invertase Is Essential for Ovule Development through Sugar Signaling Rather Than Provision of Carbon Nutrients

Publisher: Oxford University Press (OUP)

Date: 24-04-2020

DOI: 10.1104/PP.20.00400

Zoom in on Ca²⁺pattern and ion flux dynamics to decode spatial and temporal regulation of cotton fiber growth

Publisher: Cold Spring Harbor Laboratory

Date: 08-02-2021

DOI: 10.1101/2021.02.08.430284

Abstract: Cotton fibers are single-celled trichomes initiated from ovule epidermis prior to anthesis. Thereafter, the fibers undergo rapid elongation for 20 d before switching to intensive cell wall cellulose synthesis. The final length attained determines fiber yield and quality. As such, cotton fiber represents an excellent single cell model to study regulation of cell growth and differentiation, with significant agronomical implications. One major unresolved question is whether fiber elongation follows a diffusive or a tip growth pattern. We addressed this issue by using cell biology and electrophysiological approaches. Confocal imaging of Ca 2+ binding dye, fluo-3 acetoxymethyl (Fluo-3), and in situ microelectrode ion flux measurement revealed that cytosolic Ca 2+ was evenly distributed along the elongating fiber cells with Ca 2+ and H + fluxes oscillating from apical to basal regions of the elongating fibers. These findings demonstrate that, contrary to growing pollen tubes or root hairs, cotton fiber growth follows a diffusive, but not the tip growth, pattern. Further analyses showed that the elongating fibers exhibited substantial net H + efflux, indicating a strong activity of the plasma membrane H + -ATPase required for energy dependent solute uptake. Interestingly, the growing cotton fibers were responding to H 2 O 2 treatment, know to promote fiber elongation, by a massive increase in the net Ca 2+ and H + efflux in both tip and basal zones, while non-growing cells lacked this ability. These observations suggest that desensitization of the cell and a loss of its ability to respond to H 2 O 2 may be causally related to the termination of the cotton fiber elongation. Confocal imaging of Ca 2+ patterning and in situ microelectrode ion flux measurements demonstrate that, contrary to growing pollen tubes or root hairs, cotton fiber growth follows a diffusive, but not the tip growth, pattern.

Molecular regulation of sucrose catabolism and sugar transport for development, defence and phloem function

Publisher: Wiley

Date: 05-2017

DOI: 10.1111/JIPB.12539

Abstract: Sucrose (Suc) is the major end product of photosynthesis in mesophyll cells of most vascular plants. It is loaded into phloem of mature leaves for long-distance translocation to non-photosynthetic organs where it is unloaded for erse uses. Clearly, Suc transport and metabolism is central to plant growth and development and the functionality of the entire vascular system. Despite vast information in the literature about the physiological roles of in idual sugar metabolic enzymes and transporters, there is a lack of systematic evaluation about their molecular regulation from transcriptional to post-translational levels. Knowledge on this topic is essential for understanding and improving plant development, optimizing resource distribution and increasing crop productivity. We therefore focused our analyses on molecular control of key players in Suc metabolism and transport, including: (i) the identification of promoter elements responsive to sugars and hormones or targeted by transcription factors and microRNAs degrading transcripts of target genes and (ii) modulation of enzyme and transporter activities through protein-protein interactions and other post-translational modifications. We have highlighted major remaining questions and discussed opportunities to exploit current understanding to gain new insights into molecular control of carbon partitioning for improving plant performance.

Evidence That High Activity of Vacuolar Invertase Is Required for Cotton Fiber and Arabidopsis Root Elongation through Osmotic Dependent and Independent Pathways, Respectively      

Publisher: Oxford University Press (OUP)

Date: 10-08-2010

DOI: 10.1104/PP.110.162487

Abstract: Vacuolar invertase (VIN) has long been considered as a major player in cell expansion. However, direct evidence for this view is lacking due, in part, to the complexity of multicellular plant tissues. Here, we used cotton (Gossypium spp.) fibers, fast-growing single-celled seed trichomes, to address this issue. VIN activity in elongating fibers was approximately 4-6-fold higher than that in leaves, stems, and roots. It was undetectable in fiberless cotton seed epidermis but became evident in initiating fibers and remained high during their fast elongation and dropped when elongation slowed. Furthermore, a genotype with faster fiber elongation had significantly higher fiber VIN activity and hexose levels than a slow-elongating genotype. By contrast, cell wall or cytoplasmic invertase activities did not show correlation with fiber elongation. To unravel the molecular basis of VIN-mediated fiber elongation, we cloned GhVIN1, which displayed VIN sequence features and localized to the vacuole. Once introduced to Arabidopsis (Arabidopsis thaliana), GhVIN1 complemented the short-root phenotype of a VIN T-DNA mutant and enhanced the elongation of root cells in the wild type. This demonstrates that GhVIN1 functions as VIN in vivo. In cotton fiber, GhVIN1 expression level matched closely with VIN activity and fiber elongation rate. Indeed, transformation of cotton fiber with GhVIN1 RNA interference or overexpression constructs reduced or enhanced fiber elongation, respectively. Together, these analyses provide evidence on the role of VIN in cotton fiber elongation mediated by GhVIN1. Based on the relative contributions of sugars to sap osmolality in cotton fiber and Arabidopsis root, we conclude that VIN regulates their elongation in an osmotic dependent and independent manner, respectively.

Cell wall invertase as a regulator in determining sequential development of endosperm and embryo through glucose signaling early in seed development

Publisher: Informa UK Limited

Date: 2013

DOI: 10.4161/PSB.22722

Identification of regulatory networks and hub genes controlling soybean seed set and size using RNA sequencing analysis

Publisher: Oxford University Press (OUP)

Date: 13-01-2017

DOI: 10.1093/JXB/ERW460

Enhancing crop yields through improvements in the efficiency of photosynthesis and respiration

Publisher: Wiley

Date: 17-11-2023

DOI: 10.1111/NPH.18545

Abstract: The rate with which crop yields per hectare increase each year is plateauing at the same time that human population growth and other factors increase food demand. Increasing yield potential () of crops is vital to address these challenges. In this review, we explore a component of that has yet to be optimised – that being improvements in the efficiency with which light energy is converted into biomass () via modifications to CO 2 fixed per unit quantum of light ( α ), efficiency of respiratory ATP production () and efficiency of ATP use (). For α , targets include changes in photoprotective machinery, ribulose bisphosphate carboxylase/oxygenase kinetics and photorespiratory pathways. There is also potential for to be increased via targeted changes to the expression of the alternative oxidase and mitochondrial uncoupling pathways. Similarly, there are possibilities to improve via changes to the ATP costs of phloem loading, nutrient uptake, futile cycles and/or protein/membrane turnover. Recently developed high‐throughput measurements of respiration can serve as a proxy for the cumulative energy cost of these processes. There are thus exciting opportunities to use our growing knowledge of factors influencing the efficiency of photosynthesis and respiration to create a step‐change in yield potential of globally important crops.

Discovery Projects - Grant ID: DP120104148

Start Date: 02-2012

End Date: 12-2018

Amount: $270,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP180103834

Start Date: 06-2018

End Date: 05-2024

Amount: $412,121.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0989861

Start Date: 2009

End Date: 12-2010

Amount: $650,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP110104931

Start Date: 02-2011

End Date: 01-2014

Amount: $270,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0989084

Start Date: 2009

End Date: 12-2009

Amount: $275,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE140100133

Start Date: 2014

End Date: 12-2014

Amount: $230,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE110100130

Start Date: 2011

End Date: 11-2013

Amount: $500,000.00

Funder: Australian Research Council