Expression analysis of defensin-like genes (Defl) in grapevine in response to Botrytis cinerea and plant defense hormones

Defensins are a class of small, basic, cysteine-rich peptides found in plant, insect and vertebrates, which share a common tertiary structure and show broad antimicrobial activity. By using a combination of HMM and BLAST searches to scan the Vitis vinifera Pinot noir genome, 79 defensin-like sequences (DEFLs) have been identified, which correspond to 46 putative defensin genes. To better understand the involvement of this gene family in the signalling and defense against Botrytis cinerea, a necrotrophic fungus and agent of the gray rot, we investigated the changes in expression of 14 grapevine defensins in berries and inflorescences following artificial inoculation with the fungus. In parallel, we measured the content of some jasmonates (jasmonate, methyl jasmonate, OPDA) and salicylic acid (SA) in berries infected with Botrytis cinerea and tested whether these defensins are modulated by treatments with these typical mediators of defense. Among the 14 defensins, five were significantly induced upon B. cinerea infection either in inflorescences or in berries. Analytical measurements revealed that SA, JA and OPDA, but not MeJA were accumulated in infected inflorescences and berries. Preliminary data on berries treated with different hormones showed that none of the tested defensins was induced by treatment with MeJA and BTH (an analogue of salicylic acid), whereas one defensin gene was up-regulated after treatment with ethephon -a precursor of ethylene. Our results suggest a role of specific DEFLs genes in the grapevine defense against B. cinerea and the involvement of both MeJA and SA in the plant response. Preliminary data on the regulation of defensin genes by hormones have also been acquired.