Use of genes encoding cellobiohydrolase-C and topoisomerase II as targets for phylogenetic analysis and identification of Fusarium

Molecular identification and phylogenetic studies rely to a large extent on rDNA sequence polymorphism. In the field of fungal taxonomy, despite the use of huge amounts of rDNA data available, some species within a given genus remain indistinguishable. Therefore, new target sequences need to be selected and validated. This is the case for Fusarium, which includes numerous species most of which are involved in both animal and plant pathologies. In addition to the rDNA fragment encompassing the internal transcribed spacers ITS1 and ITS2 and the 5.8 S sequence, two newly characterized genes were used as molecular markers for Fusarium species genotyping. The cellobiohydrolase-C (cbh-C) and the topoisomerase II (topII) gene parts were cloned and sequenced for at least one isolate of each of the eleven different species of our collection. Both cbh-C and topII were found to be single copy genes. DNA fragments amplified by PCR in order to establish phylogenetic trees range from 1123 to 1157 bp for rDNA and from 327 to 344 bp for cbh-C (this part contains one intron). The topII gene part encoding the carboxy-terminus of the ATP binding domain of the enzyme is constant in length with a value of 724 bp. PAUP-generated phylogenetic analyses based either on cbh-C or topII data enabled all species to be distinguished, and were more informative than those resulting from rDNA sequences. Furthermore, a combination of the three datasets enhanced the accuracy of the analyses and open up new possibilities for rapid molecular identification and evolution studies within the Fusarium genus. [Copyright &y& Elsevier]