Ion Transport and Abiotic Stress Tolerance

Angiosperm plants typically harbour large numbers of Cation H⁺ eXchangers (CHXs) in their genomes, with Arabidopsis containing 28 and soybean (Glycine max) 46. Yet, the transporters have distinct roles, especially in vegetative tissues where the loss of a single CHX can lead to phenotypic defects. In soybean, varieties with a non-functional GmSALT3 (=GmCHX1) are salt-sensitive, while plants with a functional GmSALT3 are more tolerant without a yield penalty (Guan et al 2014, Qu et al 2020). CHX20 is the closest homologue of GmSALT3 in Arabidopsis and loss of CHX20 leads to defects in stomata guard cell aperture regulation (Padmanaban et al 2007). Both transporters are localised in the Endoplasmic Reticulum (ER). Using a combination of genetically encoded fluorescent sensors, physiology and biochemistry, we aim to decipher the mechanism by which these endomembrane transporters contribute to abiotic stress tolerance and cellular osmoregulation.

We have previously identified Arabidopsis Cation Chloride Cotransporter 1 (CCC1) as a missing component of the TGN/EE lumen pH regulating transporter circuit (McKay et al 2022). Plants with loss of CCC1 function show severe phenotypic defects, including a strongly reduced fertility and a highly distorted inflorescence architecture. In addition, they exhibit an altered response to salt and osmotic shock induced intracellular pH changes. Our work focuses on connecting the observed altered abiotic stress responses and decreased yield to the endomembrane localised transporter.