Most heterothallic Ascomycetes carry a single mating-type (MAT) locus with two alternate idiomorphs (MAT1-1 and MAT1-2) and sexual reproduction results when strains carrying different idiomorphs come into contact. Homothallic strains where a single individual carries both MAT1-1 and MAT 1-2 have also been described. In the genus Glomerella mating pairs in which both individuals carry MAT 1-2 have been characterized but to date the corresponding MAT1-1 idiomorph has not been identified for this genus. Both heterothallic and homothallic isolates of Glomerella have been reported, with heterothallic strains showing significant differences in fertility levels during sexual reproduction. Several models have been proposed to explain the mating system in Glomerella including: a. unbalanced heterothallism, b. the presence of multiple alleles at MAT1-2, c. the presence of more than 1 MAT locus. Although many reports exist on classical genetic analysis of mating in Glomerella, little is known in regard to the genes involved and the regulation of their expression. In order to identify and characterize genes involved in sexual reproduction in Glomerella we have generated mutants in this process for the phytopathogenic fungus Colletotrichum gloeosporioides (teleomorph, Glomerella cingulata). The mutants were obtained via Agrobacterium tumefaciens-mediated-transformation (ATMT) using ascospores of a homothallic strain of C. gloeosporioides and strain LBA4404 of A. tumefaciens carrying the binary vector pGFP-HPH (whose T-DNA contains both the green fluorescent protein (GFP) and the hygromycin B phosphotransferase (HPT) genes under the control of the Aspergillus nidulans glyceraldehyde-3-phosphate dehydrogenase promoter). ATMT of C. gloeosporioides resulted in a high transformation efficiency (1000 transformants per 106 ascospores). Putative transformants were confirmed by the detection of GFP and/or the presence of the HPT gene. This result is superior or similar to transformation efficiencies previously reported for conidia or mycelia in other Glomerella species. Screening of candidates affected in their capacity to undergo sexual reproduction is underway.
Full conference title:
9th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 9th (2008)