CAM guard cell anion channel activity follows transcript abundance and is suppressed by apoplastic malate

Lefoulon, C., Boxall, S. F., Hartwell, J. and Blatt, M. R. (2020) CAM guard cell anion channel activity follows transcript abundance and is suppressed by apoplastic malate. New Phytologist, (doi: 10.1111/nph.16640) (Early Online Publication)

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Abstract

* Plants utilizing crassulacean acid metabolism (CAM) concentrate CO2 around RuBisCO while reducing transpirational water loss associated with photosynthesis. Unlike stomata of C3 and C4 species, CAM stomata open at night for the mesophyll to fix CO2 into malate (Mal) and store it in the vacuole. CAM plants decarboxylate Mal in the light, generating high CO2 concentrations within the leaf behind closed stomata for refixation by RuBisCO. * CO2 may contribute to stomatal closure but additional mechanisms, plausibly including Mal activation of anion channels, ensure closure in the light. * In the CAM species Kalanchoë fedtschenkoi, we found that guard cell anion channel activity, recorded under voltage clamp, follows KfSLAC1 and KfALMT12 transcript abundance, declining to near‐zero by the end of the light period. Unexpectedly, however, we found that extracellular Mal inhibited the anion current of Kalanchoë guard cells, both in wild‐type and RNAi mutants with impaired Mal metabolism. * We conclude that the diurnal cycle of anion channel gene transcription, rather than the physiological signal of Mal release, is a key factor in the inverted CAM stomatal cycle.

Item Type:Articles
Status:Early Online Publication
Refereed:Yes
Glasgow Author(s) Enlighten ID:Blatt, Professor Michael and Lefoulon, Dr Cecile
Authors: Lefoulon, C., Boxall, S. F., Hartwell, J., and Blatt, M. R.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:New Phytologist
Publisher:Wiley
ISSN:0028-646X
ISSN (Online):1469-8137
Published Online:05 May 2020
Copyright Holders:Copyright © 2020 The Authors
First Published:First published in New Phytologist 2020
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
172302Dissecting a new and vital checkpoint in SNARE recycling and plant growthMichael BlattBiotechnology and Biological Sciences Research Council (BBSRC)BB/N006909/1MCSB - Plant Sciences
173107SAURs in stomatal regulation New Title: 15 NSFBIO SAUR regulation of stomatal apertureMichael BlattBiotechnology and Biological Sciences Research Council (BBSRC)BB/P011586/1MCSB - Plant Sciences
172696Synthesis of Microcompartments in Plants for Enhanced Carbon FixationMichael BlattBiotechnology and Biological Sciences Research Council (BBSRC)BB/N01832X/1MCSB - Plant Sciences