Cytosolic malate and oxaloacetate activate S‐type anion channels in Arabidopsis guard cells
Year: 2018
Type: article
Abstract: Summary Intracellular malate–starch interconversion plays an important role in stomatal movements. We investigated whether malate or oxaloacetate from the cytosolic membrane side regulate anion channels in the plasma membrane of Arabidopsis thaliana guard cells. Physiological concentrations of cytosolic malate have been reported in the range of 0.4–3 mM in leaf cells. Guard cell patch clamp and two‐electrode oocyte voltage‐clamp experiments were pursued. We show that a concentration of 1 mM cytosolic malate greatly activates S‐type anion channels in Arabidopsis thaliana guard cells. Interestingly, 1 mM cytosolic oxaloacetate also activates S‐type anion channels. Malate activation was abrogated at 10 mM malate and in SLAC 1 anion channel mutant alleles. Interestingly, malate activation of S‐type anion currents was disrupted at below resting cytosolic‐free calcium concentrations ([Ca 2+ ] cyt ), suggesting a key role for basal [Ca 2+ ] cyt signaling. Cytosolic malate was not able to directly activate or enhance SLAC 1‐mediated anion currents in Xenopus oocytes, whereas in positive controls, cytosolic Na HCO 3 enhanced SLAC 1 activity, suggesting that malate may not directly modulate SLAC 1. Cytosolic malate activation of S‐type anion currents was impaired in ost1 and in cpk5/6/11/23 quadruple mutant guard cells. Together these findings show that these cytosolic organic anions function in guard cell ‘plasma membrane’ ion channel regulation.
Source: New Phytologist
DOI: 10.1111/nph.15292
Institutions: University of California San Diego, Northwest A&F University
Language: English
Subfield: Plant Science
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2810592212