Role of Col-kin, a putative kinesin gene, in the pathogenicity of Colletotrichum sp

A heterologous transposition system was successfully developed in the Colletotrichum sp. causing olive anthracnose in southern Italy, leading to the isolation of mutants with altered virulence. The impala transposable element of Fusarium oxysporum was used for insertional mutagenesis in Colletotrichum sp. Two impala transformants, named R31 and R39, among 24 analysed, showed an altered ability to cause necrotic lesions on olives; R39 was more virulent than the wild type strain, whereas R31 resulted to be significantly less virulent. Moreover, this latter mutant was affected in the production of both conidia and appressoria whose morphology appeared different from that of the wild type strain, and furthermore they are differentiated more slowly with the respect to the wild type. In the R31 non-pathogenic mutant, the transposon flanking regions were rescued by inverse-PCR. Subsequent cloning, sequence and BLAST analysis of these regions, named Col-kin fragments, showed that the mutagenic element was inserted into a putative ORF, harbouring a conserved domain belonging to the kinesin protein family. The kinesin family are motor proteins which are involved in several fungal process such as karyogamy, nuclear division and hyphal morphogenesis. Moreover, it was shown that these proteins could be related to pathogenicity as in the case of the phytopathogenic fungus Ustilago maydis; in this pathogen a kinesin protein is required for hyphal extension and also affects fungal virulence. To demonstrate a possible involvement of the Col-kin gene in the pathogenicity of Colletotrichum sp., the inactivation of the putative kinesin gene in the wild type pathogenic strain is presently carrying out through the gene disruption strategy.