Subtilisin like proteins in the war between Grapevine and Plasmopara viticola isolates with contrasting aggressiveness

Abstract

Grapevine, one of the most important fruit crops worldwide is host to various pathogens, some of which have been spread intercontinentally in the early history of viticulture. One of the most problematic diseases is downy mildew, caused by the oomycete Plasmopara viticola (Berk. & Curt.) Berl. & de Toni which was introduced to Europe from North America in the 19th century. In addition to the establishment of chemical plant protection measures, extensive resistance breeding activities have succeeded in establishing varieties that are able to limit the propagation of this pathogen Recent studies have indicated an important role of subtilisin-like serine proteases (subtilases) in association with this increased disease tolerance. Gene expression analysis of two candidate subtilases was performed in seven cultivars with different levels of susceptibility to P. viticola. Two P. viticola isolates with different degrees of virulence were tested. Our results show that subtilases display different patterns of expression: Cucumisin exhibits peaks of expression, while VviSBT5.3a presents a bimodal behaviour. Nevertheless, both subtilases have a more pronounced response to the more virulent P. viticola isolate, which supports the hypothesis that the two subtilases are involved in the early events of the defense mechanisms.