Crassulacean acid metabolism guard cell anion channel activity follows transcript abundance and is suppressed by apoplastic malate

Lefoulon, Cecile, Boxall, Susanna F ORCID: 0000-0002-8753-101X, Hartwell, James ORCID: 0000-0001-5000-223X and Blatt, Michael R (2020) Crassulacean acid metabolism guard cell anion channel activity follows transcript abundance and is suppressed by apoplastic malate NEW PHYTOLOGIST, 227 (6). pp. 1847-1857. ISSN 0028-646X, 1469-8137

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Abstract

Plants utilising crassulacean acid metabolism (CAM) concentrate CO<inf>2</inf> around RuBisCO while reducing transpirational water loss associated with photosynthesis. Unlike stomata of C<inf>3</inf> and C<inf>4</inf> species, CAM stomata open at night for the mesophyll to fix CO<inf>2</inf> into malate (Mal) and store it in the vacuole. CAM plants decarboxylate Mal in the light, generating high CO<inf>2</inf> concentrations within the leaf behind closed stomata for refixation by RuBisCO. CO<inf>2</inf> 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:	Article
Uncontrolled Keywords:	apoplast, circadian stomatal regulation, crassulacean acid metabolism, guard cell anion channel, Kalanchoe fedtschenkoi, malic acid metabolism, voltage clamp
Depositing User:	Symplectic Admin
Date Deposited:	15 May 2020 10:32
Last Modified:	16 Jun 2026 07:29
DOI:	10.1111/nph.16640
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3087402
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