GOLDEN2-LIKE Transcription Factors Regulate WRKY40 Expression in Response to Abscisic Acid

Arabidopsis (Arabidopsis thaliana) GARP (Golden2, ARR-B, Psr1) family transcription factors, GOLDEN2-LIKE1 and -2 (GLK1/2), function in different biological processes; however, whether and how these transcription factors modulate the response to abscisic acid (ABA) remain unknown. In this study, we used a glk1 glk2 double mutant to examine the role of GLK1/2 in the ABA response. The glk1 glk2 double mutant displayed ABA-hypersensitive phenotypes during seed germination and seedling development and an osmotic stress-resistant phenotype during seedling development. Genome-wide RNA sequencing analysis of the glk1 glk2 double mutant revealed that GLK1/2 regulate several ABA-responsive genes, including WRKY40, in the presence of ABA. Chromatin immunoprecipitation and gel retardation assays showed that GLK1/2 directly associate with the WRKY40 promoter via the recognition of a consensus sequence. Additionally, RNA sequencing analysis of the glk1 glk2 double mutant and wrky40 single mutant revealed that GLK1/2 and WRKY40 control a common set of downstream target genes in response to ABA. Furthermore, results of a genetic interaction test showed that the glk1 glk2 wrky40 triple mutant displayed similar ABA hypersensitivity to the wrky40 single mutant and the glk1 glk2 double mutant, while the glk1 glk2 wrky40 abi5-c (ABI5 CRISPR/Cas9 mutant) quadruple mutant displayed similar ABA hyposensitivity to the abi5-7 single mutant. Based on these results, we propose that the GLK1/2-WRKY40 transcription module plays a negative regulatory role in the ABA response.