GABA does not regulate stomatal CO2 signalling in Arabidopsis

Adriane Piechatzek; Xueying Feng; Na Sai; Changyu Yi; Bhavna Hurgobin; Mathew Lewsey; Johannes Herrmann; Marcus Dittrich; Peter Ache; Tobias Müller; Johannes Kromdijk; Rainer Hedrich; Bo Xu; Matthew Gilliham

doi:10.1093/jxb/erae168

GABA does not regulate stomatal CO2 signalling in Arabidopsis

J Exp Bot. 2024 Apr 17:erae168. doi: 10.1093/jxb/erae168. Online ahead of print.

Authors

Adriane Piechatzek^{1

2}, Xueying Feng^{1

2}, Na Sai^{1

2}, Changyu Yi³, Bhavna Hurgobin³, Mathew Lewsey^{3

4

5}, Johannes Herrmann⁶, Marcus Dittrich^{7

8}, Peter Ache⁶, Tobias Müller⁷, Johannes Kromdijk⁹, Rainer Hedrich⁶, Bo Xu^{1

2

10}, Matthew Gilliham^{1

2

10}

Affiliations

¹ Plant Transport and Signalling Lab, ARC Centre of Excellence in Plant Energy Biology, Waite Research Institute, Glen Osmond, SA 5064, Australia.
² School of Agriculture, Food and Wine, Waite Research Precinct, University of Adelaide, Glen Osmond, SA 5064, Australia.
³ La Trobe Institute for Agriculture and Food, AgriBio Building, La Trobe University, Bundoora, VIC 3086, Australia.
⁴ Australian Research Council Research Hub for Medicinal Agriculture, AgriBio Building, La Trobe University, Bundoora, VIC 3086, Australia.
⁵ ARC Centre of Excellence in Plants for Space, AgriBio Building, La Trobe University, Bundoora, VIC 3086, Australia.
⁶ Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Würzburg 97078, Germany.
⁷ Department of Bioinformatics, University of Würzburg, Würzburg 97078, Germany.
⁸ Institute of Human Genetics, University of Würzburg, Würzburg 97074, Germany.
⁹ Department of Plant Sciences, University of Cambridge, Downing St., Cambridge, CB2 3EA, UK.
¹⁰ ARC Centre of Excellence in Plants for Space, Waite Research Institute, Glen Osmond, SA 5064, Australia.

PMID: 38628155
DOI: 10.1093/jxb/erae168

Abstract

Optimal stomatal regulation is important for plant adaptation to changing environmental conditions and for maintaining crop yield. The guard-cell signal GABA is produced from glutamate by Glutamate Decarboxylase (GAD) during a reaction that generates carbon dioxide (CO2) as a by-product. Here, we investigated a putative connection between GABA signalling and the more clearly defined CO2 signalling pathway in guard cells. The GABA-deficient mutant lines gad2-1, gad2-2 and gad1/2/4/5 were examined for stomatal sensitivity to various CO2 concentrations. Our findings show a phenotypical discrepancy between the allelic mutant lines gad2-1 and gad2-2 - a weakened CO2 response in gad2-1 (GABI_474_E05) in contrast to a wild-type response in gad2-2 (SALK_028819) and gad1/2/4/5. Through transcriptomic and genomic investigation, we traced the response of gad2-1 to a deletion of full-length Mitogen-activated protein kinase 12 (MPK12) in the GABI-KAT line, thereafter as renamed gad2-1*. Guard cell-specific complementation of MPK12 restored the gad2-1* CO2 phenotype, which confirms the proposed importance of MPK12 to CO2 sensitivity. Additionally, we found that stomatal opening under low atmospheric CO2 occurs independently of the GABA-modulated opening-channel ALMT9. Our results confirm that GABA has a role in modulating the rate of stomatal opening and closing - but not in response to CO2 per se.

Keywords: ALMTs; CO2 signalling; GABA; MPK12; genomics; stomatal movement.