Abstract

Previous studies have demonstrated that the machinery for sulfate assimilation influences the capacity of pathogenic microorganisms to invade a minor or major range of hosts, and this machinery appears to be dispensable when the lifestyle of the organism allows it. Colletotrichum lindemuthianum is the etiological agent of anthracnose, which is an important disease of beans (Phaseolus vulgaris) and an interesting model of study due to its hemibiotrophic lifestyle. We report the isolation, sequence and analysis of a 442 bp DNA fragment from the Clsir gene, which encodes the β subunit of sulfite reductase from C. lindemuthianum. The Clsir nucleotide sequence showed an identity of 97% with Trichoderma atroviride, 81% with Gibberella zeae, 77% with Penicillium chrysogenum, Arthroderma otae and 74% with Leptosphaeria maculans. In addition, we performed a phylogenetic analysis of the deduced amino acid sequence of Clsir and 48 reported SiR sequences from fungi with different lifestyles. The distance tree showed diverse clusters of fungi related with different lifestyles and host types: pathogens of animals, saprophytic/opportunistic, phytopathogens, endophytes and mycoparasites/saprophytes. The deduced amino acid sequence of ClSiR from C. lindemuthianum was grouped with the sequences of SiRs from T. atroviride, Trichoderma virens and Trichoderma reesei. Based on the fact that T. atroviride is a mycoparasite, this result suggests horizontal gene transfer.

Key words: Colletotrichum lindemuthianum, sulfite reductase, pathogen, lifestyle, host type.