Yingbai Shen

Gamma-aminobutyric acid (GABA) is a four-carbon non-protein amino acid that acts as a defense substance and a signaling molecule in various physiological processes, and which helps plants respond to biotic and abiotic stresses. This review focuses on the role of GABA’s synthetic and metabolic pathways in regulating primary plant metabolism, redistributing carbon and nitrogen resources, reducing the accumulation of reactive oxygen species, and improving plants’ tolerance of oxidative stress. This review also highlights the way in which GABA maintains intracellular pH homeostasis by acting as a buffer and activating H⁺-ATPase. In addition, calcium signals participate in the accumulation process of GABA under stress. Moreover, GABA also transmits calcium signals through receptors to trigger downstream signaling cascades. In conclusion, understanding the role of GABA in this defense response provides a theoretical basis for applying GABA in agriculture and forestry and feasible coping strategies for plants in complex and changeable environments.

Plants produce ethyl vinyl ketone (evk) in response to biotic stress, but the evk’s identification and downstream defense response remain unclear. In this paper, it is predicted by docking for the first time that evk can be recognized by RBOH protein and assist the electron transfer of RBOHD/RBOHF by binding to its FAD or NADPH binding site. Here, we show that evk treatment increased H ₂ O ₂ and intracellular calcium concentrations in Arabidopsis thaliana mesophyll cells, as observed by confocal laser scanning microscopy and non-invasive micro-test technology, and that H ₂ O ₂ signaling functioned upstream of Ca ²⁺ signaling. Yeast two-hybrid, firefly luciferase complementation imaging, and in vitro pull-down assays demonstrated that the ACA8 (AUTOINHIBITED Ca ²⁺ -ATPASE, ISOFORM 8)–CML8 (CALMODULIN-LIKE 8) interaction promoted Ca ²⁺ efflux to return Ca ²⁺ levels to the resting state. Evk treatment led to the antagonism of salicylic acid (SA) and jasmonic acid (JA). CALMODULIN 5 (CAM5) positively regulates WRKY53 expression, and CAM5 and WRKY53 positively regulate SA-related gene expression. These proteins physically interact and form a complex that is unlocked by Ca ²⁺ to release WRKY53. An electrophoretic mobility shift assay and dual-luciferase reporter assay demonstrated that WRKY53 and TGA5 cooperate to enhance the expression of the defense gene PATHOGENESIS-REALTED 1 ( PR1 ) and that WRKY53 enhances the binding of TGA5 to the PR1 promoter. This paper proposes a framework that evk, as a RES substance, can achieve plant’s ‘REScue’ through complete defense response.