GRAS-type transcription factor CaGRAS1 functions as a positive regulator of the drought response in Capsicum annuum

Transcription factor-mediated gene expression is essential for the regulation of most cellular processes, including the responses to abiotic and biotic stresses. Although a range of plant-specific GRAS transcription factors are involved in stress responses, their precise biological functions in pepper (Capsicum annuum) have yet to be ascertained. In this study, we isolated 10 pepper GRAS genes belonging to the PHYTOCHROME A SIGNAL TRANSDUCTION1 (PAT1) subfamily and identified the CaGRAS1 protein as being highly induced by abscisic acid (ABA), dehydration, and/or salt stress treatments. CaGRAS1 harbors a GRAS domain in the C-terminal region and an acidic domain in the N-terminal region, which have transcriptional activities. CaGRAS1-overexpressing (OX) Arabidopsis plants were found to show ABA-sensitive and drought-resistant phenotypes, whereas compared with wild-type plants, CaGRAS1-OX plants showed no specific phenotypic differences under high salt stress conditions. In contrast, CaGRAS1-silenced pepper plants exhibited a drought-sensitive phenotype characterized by ABA insensitivity. Furthermore, compared with control plants, we found that in response to drought stress, the expression patterns of Arabidopsis and pepper stress-responsive genes showed greater induction and reduction in CaGRAS1-OX and CaGRAS1-silenced plants, respectively. Collectively, our findings indicate that CaGRAS1 acts as a positive regulator in drought resistance by controlling the expression of stress-responsive genes.