The role of glutamate, Cyclic Guanosine Monophosphate and calcium in stomatal responses

Abstract

Stomata are microscopic pores which regulate gaseous exchange in plants. This regulation is achieved through changes in pore aperture and plants must balance aperture to optimise gaseous exchange and changing environmental condition. Stomatal aperture determined by the action of a pair of specialised cells, known as guard cells, which shrink and swell in response to environmental stimuli. Information from these stimuli is encoded by specific signals which instruct the guard cells how to respond; however, there is some heterogeneity in stomatal response – a phenomenon known as patchy stomatal conductance. Many different signalling pathways operate in guard cells, and these often interact and can also encode specificity. Cyclic Guanosine Monophosphate (cGMP) has been shown to have a role in stomatal signalling but specific aspects, particularly the role of cGMP regulatory components, remain to be studied in any great detail. In this thesis, it was demonstrated that the recently discovered cGMP phosphodiesterase (PDE1) had a role in extracellular calcium induced closure, but not in Abscisic Acid (ABA) induced closure. Furthermore, PDE1 was found to have a role in glutamate induced stomatal closure; little is known about how glutamate signalling functions in stomata, but it has been shown to function independently of ABA. Moreover, cGMP signalling components, including the guanyl cyclase (GC1) and newly discovered protein kinase G (PKG), were also shown to function in glutamate-induced stomatal closure. In addition to this, the two-pore channel (TPC1) was shown to function in glutamate induced closure and plays a role in glutamate-induced [Ca²⁺]cyt increases in guard cells. As well as these findings, the use of a new microscope known as the Mesolens was assessed for its ability to study patchy stomatal conductance.

Date of Award	21 Jun 2022
Original language	English
Awarding Institution	University of Bristol
Supervisor	Alistair Hetherington (Supervisor) & Keith Edwards (Supervisor)