Phytopathogenicity of xylella fastidiosa cvc strain: genetic analysis by gene inactivation.

Abstract

Xylella fastidiosa is the causal agent of citrus variegated chlorosis (CVC). The genome of the CVC strain 9a5c was sequenced and revealed several genes and mechanisms potentially involved in X. fastidiosa phytopathogenicity such as exopolysaccharide production, toxins and cell wall degradation. Recently, transformation of several CVC strain was obtained by Monteiro and co-workers with artificial plasmids which were found to be integrated into the chromosome by homologous recombination with one crossing-over. The main purpose of this project is to produce mutants by homologous recombination with one crossing-over in an attempt to clarify the role of genes involved in exopolysaccharide synthesis, toxins production and cell wall degradation in the phytopathogenicity of X. fastidiosa. Truncated copies of the candidate genes will be cloned into the artificial plasmids and used to inactivate the homologous genes of the wild-type strain. Mutagenesis by random insertion of transposons into the genome of X. fastidiosa will also be used to identify others genes involved in pathogenicity. Mutants will be further characterized and inoculated to periwinkle plants and citrus seedlings to evaluate their pathogenicity. (AU)