Identification of new Dickeya dadantii virulence factors secreted by the type 2 secretion system

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Liu, Lulu | Rascle, Christine | Gonçalves, Isabelle, R | Poussereau, Nathalie | Rodrigue, Agnès | Le Derout, Bastien | Condemine, Guy

Edité par CCSD -

International audience. Dickeya are plant pathogenic bacteria able to provoke disease on a wide range of plants. A type 2 secretion system (T2SS) named Out is necessary for bacterial virulence. Its study in D. dadantii showed that it secretes a wide range of plant cell wall degrading enzymes, including pectinases and a cellulase. However, the full repertoire of exoproteins it can secrete has probably not yet been identified. Secreted proteins are first addressed to the periplasm before their secretion by Out. No secretion signal present on the protein allows the identification of substrates of a T2SS. To identify new Out substrates, we analyzed D. dadantii transcriptome data obtained in plant infection condition and searched for genes strongly induced encoding a protein with a signal sequence. We identified five new Out-secreted proteins: the iron-binding protein IbpS, the expansin YoaJ, the putative virulence factor VirK and two proteins of the DUF 4879 family, SvfA and SvfB. We showed that IbpS, SvfA and SvfB are required for full virulence of D. dadantii. Homologues of IbpS are present in other phytopathogenic microorganisms (fungi and oomycetes) where they also play a role in virulence. svf genes are present in a variable number of copies in other Pectobacteriaceae, up to three in D. fanghzongdai. This work opens the way to the study of the role of non-pectinolytic proteins secreted by the Out pathway in Pectobacteriaceae.

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