L-Glutamate activates salicylic acid signalling to promote stomatal closure and PR1 expression in Arabidopsis.

Glutamate (L-Glu), an animal neurotransmitter, plays an essential role in plant signalling and regulates various plant physiological responses. We previously showed that L-Glu regulates stomatal closure in Arabidopsis via the glutamate receptor-like 3.5 gene (GLR3.5). Here, we showed that L-Glu activates salicylic acid (SA) signalling in Arabidopsis. L-Glu not only promoted stomatal closure but also triggered the expression of the PR1 gene via GLR3.5. These L-Glu-dependent actions were strongly suppressed in SA-insensitive npr1-1 and -deficient sid2-2 mutants, indicating that SA is involved in L-Glu signalling. A loss-of-function mutant of the gene encoding the SRK2E/OST1 kinase, which plays a pivotal role in abscisic acid signalling, was insensitive to both L-Glu-induced stomatal closure and PR1 expression. The glr3.5 mutants did not alleviate SA-induced stomatal closure, indicating that SA may function downstream of GLR3.5. These results indicate that L-Glu activates SA signalling, and that SRK2E/OST1 may play pivotal roles in such signalling. This article is protected by copyright. All rights reserved.