Cys2His2 zinc finger transcription factor BcabaR1 positively regulates abscisic acid production in Botrytis cinerea

Abstract

Abscisic acid (ABA) is one of the five classical phytohormones involved in increasing the tolerance of plants for various kinds of stresses caused by abiotic or biotic factors, and it also plays important roles in regulating the activation of innate immune cells and glucose homeostasis in mammals. For these reasons, as a "stress hormone," ABA has recently received attention as a candidate drug for agriculture and biomedical applications, prompting significant development of ABA synthesis. Some plant-pathogenic fungi can synthesize natural ABA. The fungus Botrytis cinerea has been used for biotechnological production of ABA. Identification of the transcription factors (TFs) involved in regulation of ABA biosynthesis in B. cinerea would provide new clues to understand how ABA is synthesized and regulated. In this study, we defined a novel Cys2His2 TF, BcabaR1, that regulates the transcriptional levels of ABA synthase genes (bcaba1, bcaba2, bcaba3, and bcaba4) in an ABA-overproducing mutant, B. cinerea TBC-A. Electrophoretic mobility shift assays revealed that recombinant BcabaR1 can bind specifically to both a 14-nucleotide sequence motif and a 39-nucleotide sequence motif in the promoter region of bcaba1 to -4 genes in vitro. A decreased transcriptional level of the bcabaR1 gene in B. cinerea led to significantly decreased ABA production and downregulated transcription of bcaba1 to -4. When bcabaR1 was overexpressed in B. cinerea, ABA production was significantly increased, with upregulated transcription of bcaba1 to -4. Thus, in this study, we found that BcabaR1 acts as a positive regulator of ABA biosynthesis in B. cinerea.