The myosin motor domain-containing chitin synthase PdChsVII is required for development, cell wall integrity and virulence in the citrus postharvest pathogen Penicillium digitatum

Chitin is an essential component of the fungal cell wall and a potential target in the development of new antifungal compounds, due to its presence in fungi and not in plants or vertebrates. Chitin synthase genes (chs) constitute a complex family in filamentous fungi and are involved in fungal development, morphogenesis, pathogenesis and virulence. In this study, additional chs genes in the citrus postharvest pathogen Penicillium digitatum have been identified. Comparative analyses included each PdChs in each one of the classes I to VII previously established, and support the grouping of these into three divisions. Disruption of the gene coding PdChsVII, which contains a short version of a myosin motor domain, has been achieved by using Agrobacterium tumefaciens-mediated transformation and revealed its role in the life cycle of the fungus. Disruption strains were viable but showed reduced growth and conidia production. Moreover, Pdchs mutants developed morphological defects as balloon-like enlarged cells and increased chitin content, indicative of an altered cell wall structure. Gene disruption also increased susceptibility to antifungal compounds such as calcofluor white (CFW), sodium dodecyl sulfate (SDS), hydroxide peroxide (H2O2) and commercial fungicides, but significantly no change was observed in the sensitivity to antifungal peptides. The PdchsVII mutants were able to infect citrus fruit and produced tissue maceration, although had reduced virulence and most importantly were greatly impaired in the production of visible mycelium and conidia on the fruit.

This work was funded by Grants BIO2009-12919 and BIO2012-34381 from the “Ministerio de Economía y Competitividad” (MINECO, Spain), and ACOMP/2011/258 and PROMETEO2010/010 from “Conselleria d’Educaciò” (Generalitat Valenciana, Comunitat Valenciana, Spain). MG was hired by the JAE-DOC postdoc program (CSIC) and EH was recipient of a scholarship within the JAE-PREDOC program (CSIC) funded both by the European FEDER funds.

Peer reviewed