Primary structure of a chitinase-encoding gene (chi1) from the filamentous fungus Aphanocladium album: similarity to bacterial chitinases.

Chitinase 1 (Chi1) is the major extracellular chitinase from the hyperparasitic fungus, Aphanocladium album. We determined the complete sequence of the chromosomal and cDNA copies of the structural gene (chi1) coding for Chi1. The coding region is interrupted by three short introns (55, 53 and 49 bp long). Chi1 is 423 aa long and begins with a stretch of 34 aa not found in the mature protein. The Chi1 sequence presents overall similarities with bacterial chitinases from Serratia marcescens and Bacillus circulans. Compared with other chitinases, A. album Chi1 has only two short similarity regions (12 and 8 aa long), which are also found in bacterial, yeast and some plant chitinases.

Phylogeny of some Fusarium species, as determined by large-subunit rRNA sequence comparison.

Fifty-two strains from eight species of Fusarium were analyzed by rapid rRNA sequencing. Two highly variable stretches (138 and 214 nucleotides) of the 5' end of the 28S-like rRNA molecule were sequenced. Such stretches permit evaluation of the divergence between closely related species and even between varieties within a species. The phylogenetic tree computed from the number of nucleotide differences shows seven Fusarium species to be more closely related to one another than the eighth species, F. nivale, is to them. On the basis of these data, we discuss both the phylogenetic value of taxonomical criteria and the impact of our findings on the demarcation of the genus Fusarium. We conclude that this method is suitable for establishing a precise phylogeny between closely related species within a genus.