ORCID Profile
0000-0002-1028-6749
Current Organisations
Australian National University
,
University of Tasmania
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Publisher: MDPI AG
Date: 18-01-2023
Abstract: Legumes are generally considered to be more responsive to elevated CO2 (eCO2) conditions due to the benefits provided by symbiotic nitrogen fixation. In response to high carbohydrate demand from nodules, legumes display autoregulation of nodulation (AON) to restrict nodules to the minimum number necessary to sustain nitrogen supply under current photosynthetic levels. AON mutants super-nodulate and typically grow smaller than wild-type plants under ambient CO2. Here, we show that AON super-nodulating mutants have substantially higher biomass under eCO2 conditions, which is sustained through increased photosynthetic investment. We examined photosynthetic and physiological traits across super-nodulating rdn1-1 (Root Determined Nodulation) and sunn4 (Super Numeric Nodules) and non-nodulating nfp1 (Nod Factor Perception) Medicago truncatula mutants. Under eCO2 conditions, super-nodulating plants exhibited increased rates of carboxylation (Vcmax) and electron transport (J) relative to wild-type and non-nodulating counterparts. The substantially higher rate of CO2 assimilation in eCO2-grown sunn4 super-nodulating plants was sustained through increased production of key photosynthetic enzymes, including Rieske FeS. We hypothesize that AON mutants are carbon-limited and can perform better at eCO2 through improved photosynthesis. Nodulating legumes, especially those with higher nitrogen fixation capability, are likely to out-perform non-nodulating plants under future CO2 conditions and will be important tools for understanding carbon and nitrogen partitioning under eCO2 conditions and future crop improvements.
Publisher: Oxford University Press (OUP)
Date: 20-02-2022
DOI: 10.1093/JXB/ERAC065
Abstract: In plants with C3 photosynthesis, increasing the diffusion conductance for CO2 from the substomatal cavity to chloroplast stroma (mesophyll conductance) can improve the efficiencies of both CO2 assimilation and photosynthetic water use. In the diffusion pathway from substomatal cavity to chloroplast stroma, the plasmalemma and chloroplast envelope membranes impose a considerable barrier to CO2 diffusion, limiting photosynthetic efficiency. In an attempt to improve membrane permeability to CO2, and increase photosynthesis in tobacco, we generated transgenic lines in Nicotiana tabacum L. cv Petite Havana carrying either the Arabidopsis PIP1 (AtPIP1 ) or PIP1 (AtPIP1 ) gene driven by the constitutive dual 2x35S CMV promoter. From a collection of independent T0 transgenics, two T2 lines from each gene were characterized, with western blots confirming increased total aquaporin protein abundance in the AtPIP1 tobacco lines. Transient expression of AtPIP1 -mGFP6 and AtPIP1 -mGFP6 fusions in Nicotiana benthamiana identified that both AtPIP1 and AtPIP1 localize to the plasmalemma. Despite achieving ectopic production and correct localization, gas exchange measurements combined with carbon isotope discrimination measurements detected no increase in mesophyll conductance or CO2 assimilation rate in the tobacco lines expressing AtPIP. We discuss the complexities associated with trying to enhance gm through modified aquaporin activity.
Publisher: Cold Spring Harbor Laboratory
Date: 06-07-2022
DOI: 10.1101/2022.07.06.498957
Abstract: Photosynthetic manipulation provides new opportunities for enhancing crop yield. However, understanding and quantifying effectively how the seasonal growth and yield dynamics of target crops might be affected over a wide range of environments is limited. Using a state-of-the-art cross-scale model we predicted crop-level impacts of a broad list of promising photosynthesis manipulation strategies for C 3 wheat and C 4 sorghum. The manipulation targets have varying effects on the enzyme-limited ( A c ) and electron transport-limited ( A j ) rates of photosynthesis. In the top decile of seasonal outcomes, yield gains with the list of manipulations were predicted to be modest, ranging between 0 and 8%, depending on the crop type and manipulation. To achieve the higher yield gains, large increases in both A c and A j are needed. This could likely be achieved by stacking Rubisco function and electron transport chain enhancements or installing a full CO 2 concentrating system. However, photosynthetic enhancement influences the timing and severity of water and nitrogen stress on the crop, confounding yield outcomes. Strategies enhancing A c alone offers more consistent but smaller yield gains across environments, A j enhancement alone offers higher gains but is undesirable in less favourable environments. Understanding and quantifying complex cross-scale interactions between photosynthesis and crop yield will challenge and stimulate photosynthesis and crop research. Leaf–canopy–crop prediction using a state-of-the-art cross-scale model improves understanding of how photosynthetic manipulation alters wheat and sorghum growth and yield dynamics. This generates novel insights for quantifying impacts of photosynthetic enhancement on crop yield across environments.
Publisher: Oxford University Press (OUP)
Date: 23-10-2018
DOI: 10.1093/JXB/ERY366
Abstract: Global food security depends on three main cereal crops (wheat, rice and maize) achieving and maintaining high yields, as well as increasing their future yields. Fundamental to the production of this biomass is photosynthesis. The process of photosynthesis involves a large number of proteins that together account for the majority of the nitrogen in leaves. As large amounts of nitrogen are removed in the harvested grain, this needs to be replaced either from synthetic fertilizer or biological nitrogen fixation. Knowledge about photosynthetic properties of leaves in natural ecosystems is also important, particularly when we consider the potential impacts of climate change. While the relationship between nitrogen and photosynthetic capacity of a leaf differs between species, leaf nitrogen content provides a useful way to incorporate photosynthesis into models of ecosystems and the terrestrial biosphere. This review provides a generalized nitrogen budget for a C3 leaf cell and discusses the potential for improving photosynthesis from a nitrogen perspective.
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.FOODCHEM.2017.10.015
Abstract: β-conglutin has been identified as a major allergen for Lupinus angustifolius seeds. The aim of this study was to evaluate the binding of IgE to five recombinant β-conglutin isoforms (rβ) that we overexpressed and purified and to their natural counterparts in different lupin species and cultivars. Western blotting suggested β-conglutins were the main proteins responsible for the IgE reactivity of the lupin species and cultivars. Newly identified polypeptides from "sweet lupin" may constitute a potential new source of primary or cross-reactive sensitization to lupin, particularly to L. albus and L. angustifolius seed proteins. Several of them exhibited qualitative and quantitative differences in IgE-binding among these species and cultivars, mainly in sera from atopic patients that react to lupin rather than peanut. IgE-binding was more consistent to recombinant β2 than to any of the other isoforms, making this protein a potential candidate for diagnosis and immunotherapy.
Publisher: Elsevier BV
Date: 05-2015
Publisher: The Royal Society
Date: 12-02-2021
Abstract: The partial pressure of CO 2 at the sites of carboxylation within chloroplasts depends on the conductance to CO 2 diffusion from intercellular airspace to the sites of carboxylation, termed mesophyll conductance ( g m ). We investigated how g m varies with leaf age and through a tobacco ( Nicotiana tabacum ) canopy by combining gas exchange and carbon isotope measurements using tunable diode laser spectroscopy. We combined these measurements with the anatomical characterization of leaves. CO 2 assimilation rate, A , and g m decreased as leaves aged and moved lower in the canopy and were linearly correlated. This was accompanied by large anatomical changes including an increase in leaf thickness. Chloroplast surface area exposed to the intercellular airspace per unit leaf area ( S c ) also decreased lower in the canopy. Older leaves had thicker mesophyll cell walls and g m was inversely proportional to cell wall thickness. We conclude that reduced g m of older leaves lower in the canopy was associated with a reduction in S c and a thickening of mesophyll cell walls.
Publisher: Frontiers Media SA
Date: 15-12-2014
Publisher: Springer Science and Business Media LLC
Date: 13-08-2010
DOI: 10.1007/S00425-010-1248-0
Abstract: The synthesis and deactivation of bioactive gibberellins (GA) are regulated by auxin and by GA signalling. The effect of GA on its own pathway is mediated by DELLA proteins. Like auxin, the DELLAs promote GA synthesis and inhibit its deactivation. Here, we investigate the relationships between auxin and DELLA regulation of the GA pathway in stems, using a pea double mutant that is deficient in DELLA proteins. In general terms our results demonstrate that auxin and DELLAs independently regulate the GA pathway, contrary to some previous suggestions. The extent to which DELLA regulation was able to counteract the effects of auxin regulation varied from gene to gene. For Mendel's LE gene (PsGA3ox1) no counteraction was observed. However, for another synthesis gene, a GA 20-oxidase, the effect of auxin was weak and in WT plants appeared to be completely over-ridden by DELLA regulation. For a key GA deactivation (2-oxidase) gene, PsGA2ox1, the up-regulation induced by auxin deficiency was reduced to some extent by DELLA regulation. A second pea 2-oxidase gene, PsGA2ox2, was up-regulated by auxin, in a DELLA-independent manner. In Arabidopsis also, one 2-oxidase gene was down-regulated by auxin while another was up-regulated. Monitoring the metabolism pattern of GA(20) showed that in Arabidopsis, as in pea, auxin can promote the accumulation of bioactive GA.
No related grants have been discovered for Victoria Clarke.