Biology subjects

Wege, S.

Publications and source records attributed to Wege, S..

9 recordsLinked to original sources

bioRxiv2025

Detection of Cytosolic Ion Concentrations by the Trans-Golgi Network/Early Endosome is Important for Salt Tolerance

Plant survival requires cellular sensing systems that detect and respond to nutrient and ion fluctuations. The ability to monitor and adjust solute concentrations is essential for managing environmental stresses, particularly salt stress, yet the molecular mechanisms underlying cellular ion sensing remain largely unknown. Here, we combine luminal pH measurements with mathematical modelling of ion transport to investigate the role of the Trans-Golgi Network/Early Endosome (TGN/EE) for cellular ion homeostasis. Our results demonstrate that cytosolic concentrations of Cl-, Na+ and K+ directly impact ion transport activity at the TGN/EE, thereby influencing luminal pH dynamics. Specifically, we find that the TGN/EE lumen becomes more alkaline when plants are exposed to elevated NaCl concentrations, indicating a previously unrecognised role for endomembrane pH regulation in salt stress responses. Furthermore, we demonstrate that TGN/EE ion transport mutants that fail to exhibit NaCl-induced alkalisation display hypersensitivity to Na+. These findings indicate that the translation of elevated cytosolic ion concentrations into TGN/EE luminal alkalisation, represents an important mechanism for conferring Na+ tolerance in plant cells.

plant biology↗

bioRxiv2024

NUDIX Hydrolases Target Specific Inositol Pyrophosphates and Regulate Phosphate and Iron Homeostasis, and the Expression of Defense Genes in Arabidopsis

Inositol pyrophosphates (PP-InsPs) are important signaling molecules that regulate diverse cellular processes in eukaryotes, including energy homeostasis, phosphate (Pi) signaling, and phytohormone perception. Yet, in plants, the enzymes responsible for their turnover remain largely unknown. Using a non-hydrolysable PP-InsP analog in a pull-down approach, we identified a family of Arabidopsis NUDIX hydrolases (NUDTs) that group into two closely related subclades. Through in vitro assays, heterologous expression systems, and higher-order gene-edited mutants, we explored the substrate specificities and physiological roles of these hydrolases. Using a combination of strong anion exchange (SAX)-HPLC, PAGE, and capillary electrophoresis electrospray ionization mass spectrometry (CE-ESI-MS), we found that their PP-InsP pyrophosphatase activity is enantiomer-selective and Mg2+-dependent. Specifically, subclade I NUDTs preferentially hydrolyze 4-InsP7, while subclade II NUDTs target 3-InsP7, with minor activity against other PP-InsPs, including 5-InsP7. In higher-order mutants of subclade II NUDTs, we observed defects in both Pi and iron homeostasis, accompanied by increased levels of 1/3-InsP7 and 5-InsP7, with a markedly larger increase in 1/3-InsP7. Ectopic expression of NUDTs from both subclades induced local Pi starvation responses (PSRs), while RNA-seq analysis comparing wildtype (WT) and subclade II nudt12/13/16 loss-of-function plants indicates additional PSR-independent roles, potentially involving 1/3-InsP7 in the regulation of plant defense. Consistently, nudt12/13/16 mutants displayed enhanced resistance to Pseudomonas syringae infection, indicating a role in bacterial pathogen susceptibility. Expanding beyond subclade II NUDTs, we demonstrated susceptibility of the 3PP-position of PP-InsPs to enzymatic activities unrelated to NUDTs, and found that such activities are conserved across plants and humans. Additionally, we found that NUDT effectors from pathogenic ascomycete fungi exhibit a substrate specificity similar to subclade I NUDTs. Collectively, our findings reveal new roles for NUDTs in PP-InsP signaling, plant nutrient and immune responses, and highlight a cross-kingdom conservation of PP-InsP-metabolizing enzymes.

plant biology↗

bioRxiv2023

PLANT UNCOUPLING MITOCHONDRIAL PROTEIN 2 localizes to the Golgi

Mitochondria act as cellular hubs of energy transformation and metabolite conversion in most eukaryotes. Plant mitochondrial electron transport chains are particularly flexible, featuring alternative components, such as ALTERNATIVE NAD(P)H DEHYDROGENASES and ALTERNATIVE OXIDASES (AOXs), that can bypass proton translocation steps. PLANT UNCOUPLING MITOCHONDRIAL PROTEINS (named PUMPs or plant UCPs) have been identified in plants as homologues of mammalian Uncoupling Proteins (UCPs), and their biochemical and physiological roles have been investigated in the context of mitochondrial energy metabolism. To dissect UCP function in Arabidopsis, the two most conserved (UCP1 and UCP2) have been targeted in recent work by combining mutant lines to circumvent potential functional redundancy in vivo. Such approaches rely on the assumption that both proteins reside in the inner mitochondrial membrane as a prerequisite for functional redundancy. Yet, contradicting results have been reported on UCP2 localization in plants. Here we provide evidence that, conversely to UCP1, which is an abundant inner mitochondrial membrane protein, UCP2 localizes to the Golgi rather than to mitochondria. Based on multiple lines of new and prior evidence, we summarize the consensus view that we have reached and provide an example of how open, critical exchange within the research community is able to constructively address ambiguities. Our observations and considerations provide direction to the ongoing discussion about the functions of UCP proteins. They further offer new perspectives for the study of Golgi membrane transport and subcellular targeting principles of membrane proteins. Since 20 to 30 % of genes in plant genomes are predicted to encode transmembrane proteins and the function of most of those proteins has not been experimentally investigated, we highlight the importance of using independent evidence for localization as a prerequisite for understanding physiological function of membrane proteins.

plant biology↗

bioRxiv2021

GmSALT3 expression improves reactive oxygen species detoxification in salt-stressed soybean roots

Soybean plants are salinity (NaCl) sensitive, with their yield significantly decreased under moderately saline conditions. GmSALT3 is the dominant gene underlying a major QTL for salt tolerance in soybean. GmSALT3 encodes a transmembrane protein belonging to the plant cation/proton exchanger (CHX) family. It is currently unknown through which molecular mechanism(s) the ER-localised GmSALT3 contributes to salinity tolerance, as its localisation excludes direct involvement in ion exclusion. In order to gain insights into potential molecular mechanism(s), we used RNA-seq analysis of roots from two soybean NILs (Near Isogenic Lines); NIL-S (salt-sensitive, Gmsalt3) and NIL-T (salt-tolerant, GmSALT3), grown under control and saline conditions (200 mM NaCl) at three time points (0h, 6h, and 3 days). Gene ontology (GO) analysis showed that NIL-T has greater responses aligned to oxidation reduction. ROS were shown less abundant and scavenging enzyme activity was higher in NIL-T, consistent with the RNA-seq data. Further analysis indicated that genes related to calcium signalling, vesicle trafficking and Casparian strip (CS) development were upregulated in NIL-T following salt treatment. We propose that GmSALT3 improves the ability of NIL-T to cope with saline stress through preventing ROS overaccumulation in roots, and potentially modulating Ca2+ signalling, vesicle trafficking and formation of diffusion barriers. HighlightRNA-seq analysis revealed that GmSALT3, which confers improved salt tolerance on soybean, improves reactive oxygen species detoxification in roots.

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↗

bioRxiv2020

A single nucleotide substitution in TaHKT1;5-D controls shoot Na+ accumulation in bread wheat

Improving salinity tolerance in the most widely cultivated cereal, bread wheat (Triticum aestivum L.), is essential to increase grain yields on saline agricultural lands. A Portuguese landrace, Mocho de Espiga Branca accumulates up to 6 folds greater leaf and sheath sodium (Na+) than two Australian cultivars, Gladius and Scout, under salt stress. Despite high leaf and sheath Na+ concentrations, Mocho de Espiga Branca maintained similar salinity tolerance compared to Gladius and Scout. A naturally occurring single nucleotide substitution was identified in the gene encoding a major Na+ transporter TaHKT1;5-D in Mocho de Espiga Branca, which resulted in a L190P amino acid residue variation. This variant prevents Mocho de Espiga Branca from retrieving Na+ from the root xylem leading to a high shoot Na+ concentration. The identification of the tissue tolerant Mocho de Espiga Branca will accelerate the development of more elite salt tolerant bread wheat cultivars.

plant biology↗

bioRxiv2020

A Grain of Salt

We quantified grain sodium (Na+) content across a barley GWAS panel grown under optimal conditions. We identified a strong association with a region containing two low and one high Na+ accumulating haplotypes of a Class 1 HIGH-AFFINITY POTASSIUM TRANSPORTER (HKT1;5) known to be involved in regulating plant Na+ homeostasis. The haplotypes exhibited an average 1.8-fold difference in grain Na+ content. We show that an L189P substitution disrupts Na+ transport in the high Na+ lines, disturbs the plasma membrane localisation typical of HKT1;5 and induces a conformational change in the protein predicted to compromise function. Under NaCl stress, lines containing P189 accumulate high levels of Na+, but show no significant difference in biomass. P189 increases in frequency from wild-species to elite cultivars leading us to speculate that the compromised haplotype is undergoing directional selection possibly due to the value of Na+ as a functional nutrient in non-saline environments.

genetics↗

bioRxiv2020

GmSALT3 confers shoot Na+ and Cl- exclusion in soybean via two distinct processes.

Soybean (Glycine max) yields are threatened by multiple stresses including soil salinity. GmSALT3 confers net shoot exclusion for both Na+ and Cl- and improves salt tolerance of soybean; however, how the ER-localised GmSALT3 achieves this is unknown. Here, GmSALT3s function was investigated in heterologous systems and near-isogenic lines that contained the full-length GmSALT3 (NIL-T; salt-tolerant) or a truncated transcript Gmsalt3 (NIL-S; salt-sensitive). GmSALT3 restored growth of K+-uptake-defective E. coli and contributed toward net influx and accumulation of Na+, K+, and Cl- in Xenopus laevis oocytes, while Gmsalt3 was non-functional. A time-course analysis of the NILs confirmed that shoot Cl- exclusion breaks down prior to Na+ exclusion, while grafting showed that shoot Na+ exclusion occurs via a root xylem-based mechanism. In contrast, NIL-T plants exhibited significantly greater Cl- content in both the stem xylem and phloem sap compared to NIL-S, indicating that shoot Cl- exclusion likely depends upon novel phloem-based Cl- recirculation. NIL-T shoots grafted on NIL-S roots contained low shoot Cl-, which confirmed that Cl- recirculation is dependent on the presence of GmSALT3 in shoots. Overall, these findings provide new insights on GmSALT3s impact on salinity tolerance and reveal a novel mechanism for shoot Cl- exclusion in plants. HighlightGmSALT3 improves soybean salt tolerance. Here, using heterologous expression, we found GmSALT3 is a functional ion transporter, and, in planta that it confers shoot salt exclusion through root-based Na+ xylem exclusion and shoot-based Cl- exclusion via phloem derived Cl- recirculation.

plant biology↗

bioRxiv2020

Endomembrane Cation Chloride Cotransporters (CCC1s) modulate endo- and exocytosis

Plant cells maintain a low luminal pH in the Trans-Golgi-Network/Early Endosome (TGN/EE), the organelle in which the secretory and endocytic pathways intersect. Impaired TGN/EE pH regulation translates into severe plant growth defects. The identity of the proton pump and proton/ion antiporters that regulate TGN/EE pH have been determined, but an essential component required to complete the TGN/EE membrane transport circuit remains unidentified - a pathway for cation and anion efflux. Here, we have used complementation, genetically encoded fluorescent sensors, and pharmacological treatments to demonstrate that the TGN/EE localised Arabidopsis Cation Chloride Cotransporter (CCC1) is this missing component necessary for regulating TGN/EE pH and function. Loss of CCC1 function leads to alterations in TGN/EE-mediated processes including endo- and exocytosis, and trafficking to the vacuole, and response to abiotic stress, consistent with the multitude of phenotypes observed in ccc1 knockout plants. This discovery places CCC1 as a central component of plant cellular function.

plant biology↗