Cys2His2 Zinc Finger Transcription Factor BcabaR1 Positively Regulates Abscisic Acid Production in Botrytis cinerea

Abscisic acid (ABA) is one of the five classical phytohormones involved in increasing the tolerance of plants to 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 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 Cys 2 His 2 transcription factor (TF) BcabaR1, which 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 bcaba1-4 genes in vitro . Decreased transcriptional level of bcabaR1 gene in B. cinerea led to significantly decreased ABA production and downregulated transcription of bcaba1-4 . When bcabaR1 was overexpressed in B. cinerea , ABA production was significantly increased with upregulated transcription of bcaba1-4 . Thus, in this study we find that BcabaR1 acts as a positive regulator toward ABA biosynthesis in B. cinerea. IMPORTANCE The abscisic acid (ABA) has a potentially important contribution to theoretical researches and applications in agriculture and medicine. Botrytis cinerea is a plant pathogenic fungus discovered to produce ABA. There has been a view that ABA is related to the interaction between pathogenic fungi and plants. Identification of regulatory genes involved in the ABA biosynthesis may facilitate to understand the underlying molecular mechanisms of ABA biosynthesis and pathogenesis about B. cinerea . Here, we presented a positive regulator BcabaR1 of ABA biosynthesis in B. cinerea , which can active the transcriptional level of ABA biosynthesis gene cluster bcaba1-4 by directly binding to the conserved sequence elements in the promoter of bcaba1-4 genes. This TF was found to be specifically involved in regulation of ABA biosynthesis. This work provides new clues for finding other ABA biosynthesis genes and improving ABA yield in B.cinerea .