GOLDEN2-LIKE Transcription Factors Regulate <i>WRKY40</i> Expression in Response to Abscisic Acid

Abstract

Arabidopsis (<i>Arabidopsis thaliana</i>) 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 <i>glk1 glk2</i> double mutant to examine the role of GLK1/2 in the ABA response. The <i>glk1 glk2</i> 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 <i>glk1 glk2</i> double mutant revealed that GLK1/2 regulate several ABA-responsive genes, including <i>WRKY40</i>, in the presence of ABA. Chromatin immunoprecipitation and gel retardation assays showed that GLK1/2 directly associate with the <i>WRKY40</i> promoter via the recognition of a consensus sequence. Additionally, RNA sequencing analysis of the <i>glk1 glk2</i> double mutant and <i>wrky40</i> 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 <i>glk1 glk2 wrky40</i> triple mutant displayed similar ABA hypersensitivity to the <i>wrky40</i> single mutant and the <i>glk1 glk2</i> double mutant, while the <i>glk1 glk2 wrky40 abi5-c</i> (<i>ABI5 CRISPR/Cas9</i> mutant) quadruple mutant displayed similar ABA hyposensitivity to the <i>abi5-7</i> single mutant. Based on these results, we propose that the GLK1/2-WRKY40 transcription module plays a negative regulatory role in the ABA response.