ORCID Profile
0000-0001-6119-8645
Current Organisation
NSW Department of Primary Industries
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Publisher: Wiley
Date: 10-05-2021
DOI: 10.1002/TPG2.20103
Abstract: MicroRNAs (miRNAs) are important regulators of biological functions in plants. To find out what roles miRNAs play in regulating symbiotic nitrogen fixation (SNF) in soybean [ Glycine max (L.) Merr.], we identified high‐confidence differentially expressed (DE) miRNAs from uninoculated roots (UR), rhizobium‐inoculated roots (IR), and nodules (NODs) of soybean by robust small RNA sequencing (sRNA‐seq). Based on their predicted target messenger RNAs (mRNAs), the expression profiles of some of these DE miRNAs could be linked to nodule functions. In particular, several miRNAs associated with nutrient transportation genes were differentially expressed in IRs and mature NODs. MiR399b, specifically, was highly induced in IRs and NODs, as well as by inorganic phosphate (Pi) starvation. In composite soybean plants overexpressing miR399b, PHOSPHATE2 ( PHO2 ), a known target of miR399b that inhibits the activities of high‐affinity Pi transporters, was strongly repressed. In addition, the overexpression of miR399b in the roots of transgenic composite plants significantly improved whole‐plant Pi and ureide concentrations and the overall growth in terms of leaf node numbers and whole‐plant dry weight. Our findings suggest that the induction of miR399b in NODs could enhance nitrogen fixation and soybean growth, possibly via improving Pi uptake to achieve a better Pi–nitrogen balance to promote SNF in nodules.
Publisher: Oxford University Press (OUP)
Date: 22-02-2023
Abstract: The mutualistic ectomycorrhizal (ECM) fungal genus Pisolithus comprises 19 species defined to date which colonize the roots of & hosts worldwide suggesting that substantial genomic and functional evolution occurred during speciation. To better understand this intra-genus variation, we undertook a comparative multi-omic study of nine Pisolithus species s led from North America, South America, Asia, and Australasia. We found that there was a small core set of genes common to all species (13%), and that these genes were more likely to be significantly regulated during symbiosis with a host than accessory or species-specific genes. Thus, the genetic “toolbox” foundational to the symbiotic lifestyle in this genus is small. Transposable elements were located significantly closer to gene classes including effector-like small secreted proteins (SSPs). Poorly conserved SSPs were more likely to be induced by symbiosis, suggesting that they may be a class of protein that tune host specificity. The Pisolithus gene repertoire is characterized by ergent CAZyme profiles when compared with other fungi, both symbiotic and saprotrophic. This was driven by differences in enzymes associated with symbiotic sugar processing, although metabolomic analysis suggest that neither copy number nor expression of these genes is sufficient to predict sugar capture from a host plant or its metabolism in fungal hyphae. Our results demonstrate that intra-genus genomic and functional ersity within ECM fungi is greater than previously thought, underlining the importance of continued comparative studies within the fungal tree of life to refine our focus on pathways and evolutionary processes foundational to this symbiotic lifestyle.
Publisher: MDPI AG
Date: 09-12-2020
DOI: 10.3390/IJMS21249378
Abstract: Nitrogen fixation in soybean consumes a tremendous amount of energy, leading to substantial differences in energy metabolism and mitochondrial activities between nodules and uninoculated roots. While C-to-U RNA editing and intron splicing of mitochondrial transcripts are common in plant species, their roles in relation to nodule functions are still elusive. In this study, we performed RNA-seq to compare transcript profiles and RNA editing of mitochondrial genes in soybean nodules and roots. A total of 631 RNA editing sites were identified on mitochondrial transcripts, with 12% or 74 sites differentially edited among the transcripts isolated from nodules, stripped roots, and uninoculated roots. Eight out of these 74 differentially edited sites are located on the matR transcript, of which the degrees of RNA editing were the highest in the nodule s le. The degree of mitochondrial intron splicing was also examined. The splicing efficiencies of several introns in nodules and stripped roots were higher than in uninoculated roots. These include nad1 introns 2/3/4, nad4 intron 3, nad5 introns 2/3, cox2 intron 1, and ccmFc intron 1. A greater splicing efficiency of nad4 intron 1, a higher NAD4 protein abundance, and a reduction in supercomplex I + III2 were also observed in nodules, although the causal relationship between these observations requires further investigation.
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/FP18200
Abstract: A major goal in agricultural research is to develop ‘elite’ crops with stronger, resilient root systems. Within this context, breeding practices have focussed on developing plant varieties that are, primarily, able to withstand pathogen attack and, secondarily, able to maximise plant productivity. Although great strides towards breeding disease-tolerant or -resistant root stocks have been made, this has come at a cost. Emerging studies in certain crop species suggest that domestication of crops, together with soil management practices aimed at improving plant yield, may hinder beneficial soil microbial association or reduce microbial ersity in soil. To achieve more sustainable management of agricultural lands, we must not only shift our soil management practices but also our breeding strategy to include contributions from beneficial microbes. For this latter point, we need to advance our understanding of how plants communicate with, and are able to differentiate between, microbes of different lifestyles. Here, we present a review of the key findings on belowground plant–microbial interactions that have been made over the past decade, with a specific focus on how plants and microbes communicate. We also discuss the currently unresolved questions in this area, and propose plausible ways to use currently available research and integrate fast-emerging ‘-omics’ technologies to tackle these questions. Combining past and developing research will enable the development of new crop varieties that will have new, value-added phenotypes belowground.
Publisher: Frontiers Media SA
Date: 02-2019
Publisher: Public Library of Science (PLoS)
Date: 08-09-2015
Publisher: Proceedings of the National Academy of Sciences
Date: 10-01-2022
Abstract: Plant genomes encode hundreds of genes controlling the detection, signaling pathways, and immune responses necessary to defend against pathogens. Pathogens, in turn, continually evolve to evade these defenses. Small RNAs, such as microRNAs (miRNAs), are one mechanism used by pathogens to overcome plant defenses and facilitate plant colonization. Mounting evidence would suggest that beneficial microbes, likewise, use miRNAs to facilitate symbiosis. Here, we demonstrate that the beneficial fungus Pisolithus microcarpus encodes a miRNA that enters plant cells and stabilizes the symbiotic interaction. These results demonstrate that beneficial fungi may regulate host gene expression through the use of miRNAs and sheds light on how beneficial microbes have evolved mechanisms to colonize plant tissues.
Publisher: MDPI AG
Date: 15-10-2015
Publisher: MDPI AG
Date: 07-02-2022
DOI: 10.3390/MICROORGANISMS10020383
Abstract: Austropuccinia psidii is a fungal plant pathogen that infects species within the Myrtaceae, causing the disease myrtle rust. Myrtle rust is causing declines in populations within natural and managed ecosystems and is expected to result in species extinctions. Despite this, variation in response to A. psidii exist within some species, from complete susceptibility to resistance that prevents or limits infection by the pathogen. Untargeted metabolomics using Ultra Performance Liquid Chromatography with Ion Mobility followed by analysis using MetaboAnalyst 3.0, was used to explore the chemical defence profiles of resistant, hypersensitive and susceptible phenotypes within Melaleuca quinquenervia during the early stages of A. psidii infection. We were able to identify three separate pools of secondary metabolites: (i) metabolites classified structurally as flavonoids that were naturally higher in the leaves of resistant in iduals prior to infection, (ii) organoheterocyclic and carbohydrate-related metabolites that varied with the level of host resistance post-infection, and (iii) metabolites from the terpenoid pathways that were responsive to disease progression regardless of resistance phenotype suggesting that these play a minimal role in disease resistance during the early stages of colonization of this species. Based on the classes of these secondary metabolites, our results provide an improved understanding of key pathways that could be linked more generally to rust resistance with particular application within Melaleuca.
Publisher: Wiley
Date: 2022
Abstract: Forest trees rely on ectomycorrhizal (ECM) fungi to obtain growth‐limiting nutrients. While addition of nitrogen (N) has the potential to disrupt these critical relationships, there is conflicting evidence as to the mechanism by which ECM:host mutualism may be affected. We evaluated how N fertilization altered host interactions and gene transcription between Eucalyptus grandis and Pisolithus microcarpus or Pisolithus albus , two closely related ECM species that typically co‐occur within the same ecosystem. Our investigation demonstrated species‐specific responses to elevated N: P. microcarpus maintained its ability to transport microbially sourced N to its host but had a reduced ability to penetrate into root tissues, while P. albus maintained its colonization ability but reduced delivery of N to its host. Transcriptomic analysis suggests that regulation of different suites of N‐transporters may be responsible for these species‐specific differences. In addition to N‐dependent responses, we were also able to define a conserved ‘core’ transcriptomic response of Eucalyptus grandis to mycorrhization that was independent of abiotic conditions. Our results demonstrate that even between closely related ECM species, responses to N fertilization can vary considerably, suggesting that a better understanding of the breadth and mechanisms of their responses is needed to support forest ecosystems into the future.
Publisher: Wiley
Date: 03-12-2020
DOI: 10.1111/PCE.13672
Abstract: Armillaria root rot is a fungal disease that affects a wide range of trees and crops around the world. Despite being a widespread disease, little is known about the plant molecular responses towards the pathogenic fungi at the early phase of their interaction. With recent research highlighting the vital roles of metabolites in plant root-microbe interactions, we sought to explore the presymbiotic metabolite responses of Eucalyptus grandis seedlings towards Armillaria luteobuablina, a necrotrophic pathogen native to Australia. Using a metabolite profiling approach, we have identified threitol as one of the key metabolite responses in E. grandis root tips specific to A. luteobubalina that were not induced by three other species of soil-borne microbes of different lifestyle strategies (a mutualist, a commensalist, and a hemi-biotrophic pathogen). Using isotope labelling, threitol detected in the Armillaria-treated root tips was found to be largely derived from the fungal pathogen. Exogenous application of d-threitol promoted microbial colonization of E. grandis and triggered hormonal responses in root cells. Together, our results support a role of threitol as an important metabolite signal during eucalypt-Armillaria interaction prior to infection thus advancing our mechanistic understanding on the earliest stage of Armillaria disease development. Comparative metabolomics of eucalypt roots interacting with a range of fungal lifestyles identified threitol enrichment as a specific characteristic of Armillaria pathogenesis. Our findings suggest that threitol acts as one of the earliest fungal signals promoting Armillaria colonization of roots.
Publisher: Wiley
Date: 16-11-2022
DOI: 10.1111/NPH.17825
Abstract: The pathways regulated in ectomycorrhizal (EcM) plant hosts during the establishment of symbiosis are not as well understood when compared to the functional stages of this mutualistic interaction. Our study used the EcM host Eucalyptus grandis to elucidate symbiosis‐regulated pathways across the three phases of this interaction. Using a combination of RNA sequencing and metabolomics we studied both stage‐specific and core responses of E. grandis during colonization by Pisolithus microcarpus . Using exogenous manipulation of the abscisic acid (ABA), we studied the role of this pathway during symbiosis establishment. Despite the mutualistic nature of this symbiosis, a large number of disease signalling TIR‐NBS‐LRR genes were induced. The transcriptional regulation in E. grandis was found to be dynamic across colonization with a small core of genes consistently regulated at all stages. Genes associated to the carotenoid/ABA pathway were found within this core and ABA concentrations increased during fungal integration into the root. Supplementation of ABA led to improved accommodation of P. microcarpus into E. grandis roots. The carotenoid pathway is a core response of an EcM host to its symbiont and highlights the need to understand the role of the stress hormone ABA in controlling host–EcM fungal interactions.
Publisher: Wiley
Date: 23-09-2020
DOI: 10.1111/NPH.16759
Abstract: Pathogenic microbes are known to manipulate the defences of their hosts through the production of secreted effector proteins. More recently, mutualistic mycorrhizal fungi have also been described as using these secreted effectors to promote host colonization. Here we characterize a mycorrhiza‐induced small secreted effector protein of 10 kDa produced by the ectomycorrhizal fungus Pisolithus albus , PaMiSSP10b. We demonstrate that PaMiSSP10b is secreted from fungal hyphae, enters the cells of its host, Eucalyptus grandis, and interacts with an S‐adenosyl methionine decarboxylase (AdoMetDC) in the polyamine pathway. Plant polyamines are regulatory molecules integral to the plant immune system during microbial challenge. Using biochemical and transgenic approaches we show that expression of PaMiSSP10b influences levels of polyamines in the plant roots as it enhances the enzymatic activity of AdoMetDC and increases the biosynthesis of higher polyamines. This ultimately favours the colonization success of P. albus . These results identify a new mechanism by which mutualistic microbes are able to manipulate the host´s enzymatic pathways to favour colonization.
Publisher: Elsevier BV
Date: 02-2022
Publisher: Cold Spring Harbor Laboratory
Date: 13-11-2022
DOI: 10.1101/2022.11.10.515791
Abstract: Members of the fungal genus Armillaria are necrotrophic pathogens with efficient plant biomass-degrading strategies. The genus includes some of the largest terrestrial organisms on Earth, spreading underground and causing tremendous losses in erse ecosystems. Despite their global importance, the mechanism by which Armillaria evolved pathogenicity in a clade of dominantly non-pathogenic wood-degraders (Agaricales) remains elusive. Here, using new genomic data, we show that Armillaria species, in addition to widespread gene duplications and de novo gene origins, appear to have at least 775 genes that were acquired via 101 horizontal gene transfer (HGT) events, primarily from Ascomycota. Functional and expression data suggest that HGT might have affected plant biomass-degrading and virulence abilities of Armillaria , two pivotal traits in their lifestyle. We further assayed gene expression during root and cambium colonization, and report putative virulence factors, extensive regulation of horizontally acquired and wood-decay related genes as well as novel pathogenicity-induced small secreted proteins (PiSSPs). Two PiSSPs induced necrosis in live plants, suggesting they are potential virulence effectors conserved across Armillaria . Overall, this study details how evolution knitted together horizontally and vertically inherited genes in complex adaptive traits, such as plant biomass degradation and pathogenicity, paving the way for development of infection models for one of the most influential pathogens of temperate forest ecosystems.
Publisher: Elsevier BV
Date: 12-2020
No related grants have been discovered for Johanna Wing-Hang Wong.