Biology subjects

Tyerman, S. D.

Publications and source records attributed to Tyerman, S. D..

5 recordsLinked to original sources

bioRxiv2023

Barley HvNIP2;1 aquaporin permeates water, metalloids, saccharides, and ion pairs due to structural plasticity and diversification

Aquaporins can facilitate the passive movement of water and small polar molecules and some ions. The barley Nodulin 26-like Intrinsic Protein (HvNIP2;1) embedded in liposomes and examined through stopped-flow light scattering spectrophotometry and Xenopus oocyte swelling assays was found to permeate water, boric and germanic acids, sucrose and L-arabinose 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 (lactose, cellobiose, gentiobiose, trehalose), trisaccharide raffinose, and urea, glycerol, and acyclic polyols were permeated to a much lower extent. Apparent permeation of hydrated KCl and MgSO4 ion pairs was observed, while CH3COONa and NaNO3 permeated at significantly lower rates. Experiments with boric acid and sucrose revealed no apparent interaction between solutes when permeated together, and AgNO3 blocked the permeation of all solutes. Full-scale steered molecular dynamics simulations of HvNIP2;1 and spinach SoPIP2;1 revealed possible rectification for water, boric acid, and sucrose transport, and defined key residues interacting with permeants. In a biological context, the simulated sucrose rectification could mediate its apoplastic-to-intracellular transport but not the reverse, thus, constituting a novel element of plant saccharide-transporting machinery. Phylogenomic analyses of 164 Viridiplantae and 2,993 Archaean, bacterial, fungal, and Metazoan aquaporins rationalised 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 sustained food production. Significance StatementAquaporins are fundamental to water and solute movements in nearly all living organisms. Solute selectivity inspections of the HvNIP2;1 aquaporin revealed that it transported water, hydroxylated metalloids boric and germanic acids, sucrose, L-arabinose, KCl, and MgSO4 ion pairs, but not D-glucose or D-fructose and to lesser extent urea, and acyclic polyols. This poly-selective transport by HvNIP2;1 classified in the NIP3 sub-clade aquaporins may afford nutritional and protective roles during plant development and in response to abiotic stresses. It is anticipated that the solute specificity definition of HvNIP2;1 inspires protein engineering and in silico mining to develop plants, which when exposed to suboptimal soil conditions of high soil metalloids, would overcome toxicity for sustained food production.

biophysics↗

bioRxiv2022

The wheat multi-pathogen resistance gene, Lr67res, confers a novel gain-of-function phenotype involving anion fluxes

Partial resistance to multiple biotrophic fungal pathogens in wheat (Triticum aestivum L.) is conferred by the Lr67 gene, which encodes a Sugar Transport Protein 13 (STP13) family hexose-proton symporter variant. Two mutations (G144R, V387L) differentiate the resistant and susceptible protein variants (Lr67res and Lr67sus). The molecular function of the Lr67res protein is not well understood. We functionally characterized the wheat Lr67res protein variant using two heterologous expression systems - Xenopus laevis oocytes and Saccharomyces cerevisiae yeast. Wheat and barley (Hordeum vulgare) were used to verify disease resistance capability of Lr67/STP13 variants. The Lr67res allele, but not Lr67sus, induced large sugar-independent, anion-dominated currents in oocytes and an increased sensitivity to ions in yeast, implicating a novel gain-of-function. We demonstrate that the single mutant variant, Lr67susG144R, confers disease resistance in wheat and that transgenic barley (Hordeum vulgare L.) plants expressing the orthologous HvSTP13 gene carrying the equivalent mutations present in Lr67res exhibited increased resistance to Puccinia hordei. NaCl treatment was found to induce leaf tip necrosis in Lr67res wheat. An Lr67res-like gain-of-function can be introduced into orthologous plant hexose transporters via single amino acid mutation, highlighting the possibility of generating disease resistance in other crop species, especially with gene editing. One sentence summaryThe wheat Lr67res protein responsible for multipathogen resistance has a gain-of-function over the Lr67sus protein, that is associated with anion fluxes and likely contributes to disease resistance.

plant biology↗

bioRxiv2020

Identification of a unique ZIP transporter involved in zinc uptake via the arbuscular mycorrhizal fungal pathway

Low soil zinc (Zn) availability is a limiting factor for crop yield, and increasing Zn content is a major target for the biofortification of major crops. Arbuscular mycorrhizal (AM) fungi associate with the roots of most terrestrial plant species and improve the host plants growth and nutrition through the mycorrhizal pathway of nutrient uptake. Although the physiology of Zn uptake through the mycorrhizal pathway is well established, the identity of the molecular components responsible for Zn transport in the mycorrhizal pathway are unknown. RNA-seq analysis identified the putative Zn transporter gene MtZIP14 by its marked up-regulation in Medicago truncatula roots when colonised by the AM fungus Rhizophagus irregularis under varying soil Zn supply. Expression of GFP-tagged MtZIP14 in roots revealed that it is exclusively localised to the site of plant-fungal nutrient exchange in cortical cells, the peri-arbuscular membrane. Expression of MtZIP14 in a yeast mutant lacking Zn transport function restored growth under low Zn availability. M. truncatula MtZIP14 loss-of-function mutants had reduced shoot biomass compared to the wild-type when colonised by AM fungi and grown under low Zn. Vesicular and arbuscular colonisation, but not hyphal colonisation, were also lower in mtzip14 mutant plants. Based on these results we propose that MtZIP14 plays a key role in the transport of Zn from AM fungus to plant across the peri-arbuscular membrane, and MtZIP14 function is crucial to plant competitiveness in a low Zn soil. Significance statementMajority of crop plant species associate with arbuscular mycorrhizal fungi, which can increase plant nutrient uptake. Improving our knowledge of how Zn is taken up in mycorrhizal plants will lead to improved plant and human Zn nutrition outcomes. Here, we report a novel plant transporter with a major role in Zn nutrition of mycorrhizal plants. MtZIP14 is involved in Zn transport, is exclusively localised to the specialised plant-fungal interface in roots, and impairment of MtZIP14 gene function results in negative impacts on both plant growth and Zn nutrition.

plant biology↗

bioRxiv2017

A comparison of root and shoot hydraulics, aquaporin expression and leaf gas exchange between two grapevine cultivars reveals differences in hydraulic control mediated by aquaporins

Hydraulics of plants that take different strategies of stomatal control under water stress are still relatively poorly understood. Here we explore how root and shoot hydraulics, gas exchange, aquaporin expression and abscisic acid (ABA) concentration in leaf xylem sap ([ABA]xylem) may be involved and coordinated. A comparison in responses to mild water stress and ABA application was made between two cultivars of Vitis vinifera L. previously classified as isohydric (Grenache) and anisohydric (Syrah). Grenache showed stronger adjustments of leaf, plant, and root hydraulic conductances to decreased soil moisture and a steeper correlation of stomatal conductance (gs) to [ABA]xylem than Syrah resulting in greater conservation of soil moisture, but not necessarily more isohydric behaviour. Under well-watered conditions, changes in vapour pressure deficit (VPD) had a strong influence on gs in both cultivars with adjustments of leaf hydraulic conductance. Grenache was more sensitive to decreases in soil water availability compared to Syrah that rather responded to VPD. There were stronger correlations between plant hydraulic parameters and changes in aquaporin gene expression in leaves and roots of Grenache. Overall, the results reinforce the hypothesis that both hydraulic and chemical signals significantly contribute to the differences in water conservation behaviours of the two cultivars.

plant biology↗

bioRxiv2017

Split personality of Aluminum Activated Malate Transporter family proteins: facilitation of both GABA and malate transport

Plant aluminum activated malate transporters (ALMTs) are currently classified as anion channels; they are also known to be regulated by diverse signals leading to a range of physiological responses. Gamma-aminobutyric acid (GABA) regulation of anion flux through ALMT proteins requires the presence of a specific amino acid motif in ALMTs that shares similarity with a GABA-binding site in mammalian GABAA receptors. Here, we explore why TaALMT1-activation leads to a negative correlation between malate efflux and endogenous GABA concentrations ([GABA]i) in both wheat root tips and in heterologous expression systems. We show that TaALMT1 activation reduces [GABA]i because TaALMT1 facilitates GABA efflux. TaALMT1-expression also leads to GABA transport into cells, demonstrated by a yeast complementation assay and via 14CGABA uptake into TaALMT1-expressing Xenopus laevis oocytes; this was found to be a general feature of all ALMTs we examined. Mutation of the GABA motif (TaALMT1F213C) prevented both GABA influx and efflux, and uncoupled the relationship between malate efflux and [GABA]i. We conclude that ALMTs are likely to act as both GABA and anion transporters in planta. GABA and malate appear to interact with ALMTs in a complex manner regulating each others transport, suggestive of a role for ALMTs in communicating metabolic status.

plant biology↗