The taxon-specific paralogs of grapevine PRLIP genes are highly induced upon powdery mildew infection

Abstract

PRLIP (pathogenesis-related lipase) is a gene family encoding class 3 lipase-like proteins originally described and first characterized in Arabidopsis thaliana. Nine paralog genes of Arabidopsis can be separated into two groups based on expression characteristics and pathogen responses. Genes of Group 1 are clustered on chromosome 5 and show either high inducibility to different stress hormones and in response to pathogen attack or are undetectable at the transcript level. Group 2 contains the remaining genes, spread over the genome and are expressed constitutively in all the tissues tested. The aim of the present study was to determine the distribution of these two groups among plants, and to verify their differential expression. Orthologs of constitutively active members (Group 2) were found in all angiosperms, with available genome sequences. They are referred to as "core PRLIPs". In contrast, the gene cluster containing the pathogen-inducible PRLIPs (Group 1) was unique for Arabidopsis. Among other angiosperms, grapevine also possesses such a unique genome-specific group of PRLIP genes. To investigate whether these genes are also counterparts in pathogen responses, their expression pattern was tested under stress conditions. Two of the specific Vitis PRLIPs were highly induced in response to both powdery mildew infection and benzothiadiazole (BTH) treatment. Core Vitis PRLIPs, however, were not responsive to either pathogen attack or the chemical inducer. Our data provide insights into the distribution of a pathogenesis-related gene family in different plant lineages, and might reveal common characteristics with other inducible defense-related gene families.