Cold induced Botrytis cinerea enolase (BcEnol-1) functions as a transcriptional regulator and is controlled by cAMP

Botrytis cinerea is a necrotrophic fungal plant pathogen that can survive, grow and infect crops under cold stress. In an attempt to understand the molecular mechanisms leading to cold tolerance of this phytopathogen, we identified an enolase, BcEnol-1. BcEnol-1 encodes a 48 kDa protein that shows high identity to yeast, Arabidopsis and human enolases (72, 63 and 63%, respectively). Northern analysis confirms that an increase in transcript abundance of BcEnol-1 was observed when B. cinerea mycelium was shifted from 22 to 4°C. In order to understand its regulation during cold stress, BcEnol-1 expression was studied in B. cinerea mutants viz Δbcg1 (mutant of B. cinerea for bcg1), Δbcg3 (mutant of B. cinerea for bcg3) and Δbac (mutant of B. cinerea for adenylate cyclase). A decrease in enolase expression in these mutants was observed during cold stress suggesting enolase activation by a cAMP mediated cascade. Expression of enolase was restored with the exogenous addition of cAMP to the Δbac mutant. Recombinant enolase protein was also found to bind to the promoter elements of transcripts belonging to the Zinc-C₆ protein family and calpain like proteases. Based on these results we conclude that enolase from Botrytis is cold responsive, influenced by cAMP and acts putatively as a transcriptional regulator.