77 research outputs found
Water flow in the roots of crop species: The influence of root structure, aquaporin activity, and waterlogging
No full textCopyright © 2007 Elsevier Inc. All rights reserved.The hydraulic properties of plant roots depend on the morphology and anatomy of the root system, the length of the absorbing region and the influence of aquaporins (AQPs). These features change during development and in response to environmental stimuli, and alter the hydraulic conductivity of the root system (Lpr). AQPs are proteins that form water selective channels to facilitate water flow across membranes. A large proportion of AQP isoforms are predominantly expressed in roots and their localization indicates a putative role in the transport of water across the root. AQP activity can finely regulate the rate of water flow across the root by changes in abundance and opening/closing the water channels. Since water will flow by the pathway of least resistance, AQPs will only influence radial water flow if the hydraulic conductivity of the apoplast is relatively less than that of the cell-to-cell pathway. There is growing evidence that AQPs influence water flow through the roots of some, but not all, species. Waterlogging is a significant environmental constraint to crop growth, but its influence on Lpr is poorly understood. Depending on the tolerance of the species, waterlogging through oxygen deficiency reduces root growth and tends to reduce Lpr. Oxygen deficiency can directly or indirectly close AQPs or alter their abundance. Changes in AQP activity may be the key component which ultimately influences water transport through waterlogged roots. © 2007 Elsevier Inc. All rights reserved.H. Bramley, D.W. Turner, S.D. Tyerman and N.C. Turne
Differential fruitset between grapevine cultivars is related to differences in pollen viability and amine concentration in flowers
No full textVersion of Record online: 12 NOV 2015Background and Aims: Reproductive capacity among grapevine cultivars varies considerably and impacts yield. Bioactive amines are reported to be involved in many aspects of plant reproductive physiology. We aimed to examine the association between the reproductive performance of cultivars and the concentration of amines in the reproductive organs. Methods and Results: The reproductive performance of Shiraz, Merlot and Cabernet Sauvignon was assessed by determining fruitset, coulure index, millerandage index, pollen tube growth and stigma receptivity. Endogenous concentration of amines in flowers and berries was measured. Poor reproductive performance exhibited by Cabernet Sauvignon and Merlot compared with that of Shiraz was correlated with poor pollen viability. Amine profiles in the flowers and berries varied significantly among cultivars. A significantly higher concentration of diaminopropane was found in Merlot and Cabernet Sauvignon and correlated with a higher proportion of underdeveloped berries. An aromatic amine phenylethylamine was found to be the major free amine in the flowers of Merlot, a cultivar susceptible to poor fruitset. Conclusion: Variable reproductive performance exhibited by grapevine cultivars is related to differences in pollen viability and amine concentration in the reproductive organs. Significance of the Study: A better understanding of the association between reproductive performance and amines in the reproductive organs of grapevines has been achieved.T. Baby, M. Gilliham, S.D. Tyerman and C. Collin
The VvBAP1 gene is identified as a potential inhibitor of cell death in grape berries
No full textCell death (CD) in Vitis vinifera L grape berries, exemplified in Shiraz, occurs late in ripening influencing yield, berry and wine quality. Here we isolated and functionally characterised a BON1-associated gene, VvBAP1 from Shiraz berries, encoding a small protein with a C2 domain. VvBAP1 transcript increased during fruit development from veraison to harvest, and was significantly inhibited by drought stress 92 days after flowering when CD normally begins. This was correlated with high CD in Shiraz berries. The agrobacterium-mediated transient expression of VvBAP1 in tobacco leaves led to a decrease in electrolyte leakage and downregulated a marker gene (Hsr203J) for cell death. Expressing VvBAP1 in yeast (Saccharomyces cerevisiae) also alleviated cell death induced by hydrogen peroxide (H₂O₂). Overexpression of VvBAP1 in Arabidopsis increased resistance to H₂O₂ and reduced CD due to higher expression of genes involved in anti-oxidative responses. Arabidopsis overexpressing VvBAP1 displayed higher tolerance to drought accompanied by upregulation of antioxidant-related gene expression. VvBAP1 complemented an Arabidopsis bap1 knockout by abolishing its CD phenotypes. These results indicate that VvBAP1 may play a role in alleviating CD in grape berries and its downregulation under drought stress may be responsible for the generally observed increase in CD within the berry.Shifeng Cao, Zeyu Xiao, Vladimir Jiranek and Stephen D. Tyerma
Cytosolic GABA inhibits anion transport by wheat ALMT1
No full textFirst published: 07 October 2019.
Corrected by: Corrigendum: Cytosolic GABA inhibits transport by wheat ALMT1 (vol 225, pg 671, 2020), in Early view - https://doi.org/10.1111/nph.18214. Since its publication, the authors of Long et al. (2020) have brought to our attention an error in their article. In the Acknowledgements section, the support for the work from the Australian Research Council Centre of Excellence funding to Matthew Gilliham and Stephen Tyerman was incorrectly listed under the number ‘CE14010008’. The correct funding number is ‘CE140100008’, and the corrected Acknowledgements section is shown below. We apologize to our readers for this mistake.Anion transport by Aluminium-activated malate transporter (ALMT) proteins is negatively regulated by gamma-aminobutyric acid (GABA), which increases in concentration during stress. Here, the interaction between GABA and wheat (Triticum aestivum, Ta) TaALMT1 heterologously-expressed in Xenopus laevis oocytes was investigated. GABA inhibited anion transport by TaALMT1 in membrane patches from the cytosolic, not extracellular membrane face, via a reduction in open probability (NPopen ), not an inhibition of channel current magnitude. TaALMT1 currents in patches frequently exhibited rundown with complete removal of cytosolic factors, but were partially sustained by protein kinase C dependent phosphorylation. When applied to whole oocytes a GABA-analogue-BODIPY conjugate inhibited TaALMT1 anion currents from the cytoplasmic face only, whereas free GABA inhibited from both the inside and outside consistent with GABA traversing the TaALMT1 pore then acting from the inside. We propose GABA does not competitively inhibit ALMT conductance through the same pore but rather leads to an allosteric effect, reducing anion channel opening frequency. Across plants GABA is a conserved regulator of anion transport via ALMTs - a family with numerous physiological roles beyond Al3+ tolerance. Our data suggests that a GABA-ALMT interaction from the cytosolic face has the potential to form part of a novel plant signalling pathway.Yu Long, Stephen D. Tyerman, Matthew Gilliha
Role of TaALMT1 malate-GABA transporter in alkaline pH tolerance of wheat
No full textMalate exudation through wheat (Triticum aestivum L) Aluminium-activated Malate Transporter 1 (TaALMT1) confers Al³⁺ tolerance at low pH, but is also activated by alkaline pH, and is regulated by and facilitates significant transport of gamma-aminobutyric acid (GABA, a zwitterionic buffer). Therefore, TaALMT1 may facilitate acidification of an alkaline rhizosphere by promoting exudation of both malate and GABA. Here, the performance of wheat near isogenic lines (NILs) ET8 (Al⁺³ -tolerant, high TaALMT1 expression) and ES8 (Al⁺³ -sensitive, low TaALMT1 expression) are compared. Root growth (at 5-weeks) was higher for ET8 than ES8 at pH 9. ET8 roots exuded more malate and GABA at high pH and acidified the rhizosphere more rapidly. GABA and malate exudation was enhanced at high pH by the addition of aluminate in both ET8 and transgenic barley expressing TaALMT1. Xenopus laevis oocytes expressing TaALMT1 acidified an alkaline media more rapidly than controls corresponding to higher GABA efflux. TaALMT1 expression did not change under alkaline conditions but key genes involved in GABA turnover changed in accord with a high rate of GABA synthesis. We propose that TaALMT1 plays a role in alkaline tolerance by exuding malate and GABA, possibly coupled to proton efflux.Muhammad Kamran, Sunita A. Ramesh, Matthew Gilliham, Stephen D. Tyerman, Jayakumar Bos
Roles of membrane transporters: connecting the dots from sequence to phenotype
No full textBackground: Plant membrane transporters are involved in diverse cellular processes underpinning plant physiology, such as nutrient acquisition, hormone movement, resource allocation, exclusion or sequestration of various solutes from cells and tissues, and environmental and developmental signalling. A comprehensive characterization of transporter function is therefore key to understanding and improving plant performance. Scope and conclusions: In this review, we focus on the complexities involved in characterizing transporter function and the impact that this has on current genomic annotations. Specific examples are provided that demonstrate why sequence homology alone cannot be relied upon to annotate and classify transporter function, and to show how even single amino acid residue variations can influence transporter activity and specificity. Misleading nomenclature of transporters is often a source of confusion in transporter characterization, especially for people new to or outside the field. Here, to aid researchers dealing with interpretation of large data sets that include transporter proteins, we provide examples of transporters that have been assigned names that misrepresent their cellular functions. Finally, we discuss the challenges in connecting transporter function at the molecular level with physiological data, and propose a solution through the creation of new databases. Further fundamental in-depth research on specific transport (and other) proteins is still required; without it, significant deficiencies in large-scale data sets and systems biology approaches will persist. Reliable characterization of transporter function requires integration of data at multiple levels, from amino acid residue sequence annotation to more in-depth biochemical, structural and physiological studies.Rakesh David, Caitlin S. Byrt, Stephen D. Tyerman, Matthew Gilliham, and Stefanie Weg
Barley Nodulin 26-like intrinsic protein permeates water, metalloids, saccharides, and ion pairs due to structural plasticity and diversification
No full textPublished, Papers in Press, October 31, 2023,Aquaporins can facilitate the passive movement of water, small polar molecules and some ions. Here, we examined solute selectivity for the barley Nodulin 26-like Intrinsic Protein (HvNIP2;1) embedded in liposomes and examined through stopped-flow light scattering spectrophotometry and Xenopus laevis oocyte swelling assays. We found that HvNIP2;1 permeates water, boric and germanic acids, sucrose, and lactose but not d-glucose or d-fructose. Other saccharides, such as neutral (d-mannose, d-galactose, d-xylose, d-mannoheptaose) and charged (N-acetyl d-glucosamine, d-glucosamine, d-glucuronic acid) aldoses, disaccharides (cellobiose, gentiobiose, trehalose), trisaccharide raffinose, and urea, glycerol, and acyclic polyols were permeated to a much lower extent. We observed apparent permeation of hydrated KCl and MgSO4 ions, while CH3COONa and NaNO3 permeated at significantly lower rates. Our experiments with boric acid and sucrose revealed no apparent interaction between solutes when permeated together, and AgNO3 or H[AuCl4] blocked the permeation of all solutes. Docking of sucrose in HvNIP2;1 and spinach water-selective SoPIP2;1 aquaporins revealed the structural basis for sucrose permeation in HvNIP2;1 but not in SoPIP2;1, and defined key residues interacting with this permeant. In a biological context, sucrose transport could constitute a novel element of plant saccharide-transporting machinery. Phylogenomic analyses of 164 Viridiplantae and 2,993 Archaean, bacterial, fungal, and Metazoan aquaporins rationalized solute poly-selectivity in NIP3 sub-clade entries and suggested that they diversified from other sub-clades to acquire a unique specificity of saccharide transporters. Solute specificity definition in NIP aquaporins could inspire developing plants for food production.Akshayaa Venkataraghavan, Julian G. Schwerdt, Stephen D. Tyerman, Maria
Hrmov
Tree water sources over shallow, saline groundwater in the lower River Murray, south-eastern Australia: implications for groundwater recharge mechanisms
No full textThe decline of riparian vegetation in the lower River Murray, south-eastern Australia, is associated with a reduction in flooding frequency, extent and duration, and increased salt accumulation. The plant water sources of healthy Eucalyptus largiflorens trees growing over highly saline (>40 dS m⁻¹) groundwater were investigated during summer when water deficit is greatest. The study found low-salinity soil water overlying highly saline groundwater at most sites. This deep soil water, rather than the saline groundwater, was identified as the plant water source at most sites. Stable isotopes of water and water potential measurements were used to infer how the deep soil water was recharged. The low-salinity, deep soil water was recharged in the following two ways: (1) vertically through the soil profile or via preferential flow paths by rainfall or flood waters or (2) horizontally by bank recharge from surface water on top of the saline groundwater. Vertical infiltration of rainfall and floodwaters through cracking clays was important for trees growing in small depressions, whereas infiltration of rainfall through sandy soils was important for trees growing at the break of slope. Bank recharge was important for trees growing within ~50 m of permanent and ephemeral water bodies. The study has provided a better understanding of the spatial patterns of recharge at a scale relevant to riparian vegetation. This understanding is important for the management of floodplain vegetation growing in a saline, semi-arid environment.K.L. Holland, S.D. Tyerman, L.J. Mensforth and G.R. Walke
Root ideotype influences nitrogen transport and assimilation in maize
No full textPublished: 24 April 2018Maize (Zea mays, L.) yield is strongly influenced by external nitrogen inputs and their availability in the soil solution. Overuse of nitrogen-fertilizers can have detrimental ecological consequences through increased nitrogen pollution of water and the release of the potent greenhouse gas, nitrous oxide. To improve yield and overall nitrogen use efficiency (NUE), a deeper understanding of nitrogen uptake and utilization is required. This study examines the performance of two contrasting maize inbred lines, B73 and F44. F44 was selected in Florida on predominantly sandy acidic soils subject to nitrate leaching while B73 was selected in Iowa on rich mollisol soils. Transcriptional, enzymatic and nitrogen transport analytical tools were used to identify differences in their N absorption and utilization capabilities. Our results show that B73 and F44 differ significantly in their genetic, enzymatic, and biochemical root nitrogen transport and assimilatory pathways. The phenotypes show a strong genetic relationship linked to nitrogen form, where B73 showed a greater capacity for ammonium transport and assimilation whereas F44 preferred nitrate. The contrasting phenotypes are typified by differences in root system architecture (RSA) developed in the presence of both nitrate and ammonium. F44 crown roots were longer, had a higher surface area and volume with a greater lateral root number and density than B73. In contrast, B73 roots (primary, seminal, and crown) were more abundant but lacked the defining features of the F44 crown roots. An F1 hybrid between B73 and F44 mirrored the B73 nitrogen specificity and root architecture phenotypes, indicating complete dominance of the B73 inbred. This study highlights the important link between RSA and nitrogen management and why both variables need to be tested together when defining NUE improvements in any selection program.Julie Dechorgnat, Karen L. Francis, Kanwarpal S. Dhugga, J. A. Rafalski, Stephen D. Tyerman and Brent N. Kaise
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