Stomatal glutamate signalling and the role of AtPKG in the control of gene expression.

Abstract

Regulation of stomatal opening is essential to control gaseous exchange, water loss and hence is integral to plant productivity. Stomata comprise of two guard cells flanking a central pore, with a variable aperture that is modulated by complex signalling networks. Uniquely for an amino acid, glutamate (Glu) is both a key metabolite and signalling molecule within plants, found to mediate stomatal closure. Whilst the signalling role of Glu has been extensively characterised in animals, its role in plants is largely unexplored. Thus, here using A. thaliana I investigated the signalling components that mediate guard cell response to L-Glu. I provide evidence for an essential role for respiratory burst oxidase homologues (RBOH) RBOHD and RBOHF, and the protein kinase OST1, in L-Glu-induced stomatal closure. In addition, building on the central role of Ca2+ in this guard cell response, I used the genetically encoded Ca2+ indicator R-GECO1 to reveal the interdependence of ROS and Ca2+ in Glu-induced stomatal closure. Finally, due to the essential role of cGMP activated protein kinase (PKG) in L-Glu-induced stomatal closure, I identified candidate gene targets of AtPKG using transcriptome analysis of Atpkg-1 and Atpkg-2. Vitally, I find PKG is associated with downstream SA-, ion homeostasis-, ribosomal- and chloroplast structural processes- gene networks. This links AtPKG to previously elucidated cGMP-dependent processes and provides novel evidence of the unexplored role of PKG in A. thaliana. Together these findings develop understanding of the molecular toolkit fine-tuning stomatal responses to Glu.

Date of Award	3 Oct 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Alistair Hetherington (Supervisor)