A strain-specific cyclin homolog in the fungal phytopathogen Colletotrichum gloeosporioides.

The fungus, Colletotrichum gloeosporioides, which infects the tropical pasture legume, Stylosanthes guianensis, contains highly variable mini-chromosomes. The transcription of strain-specific genomic DNA clones previously isolated from one variable mini-chromosome was investigated by using these clones to screen a cDNA library prepared from the fungus grown in liquid medium. A cDNA clone was obtained with one of the genomic clones and was sequenced. A single long open reading frame of 259 amino acids (aa) was detected with significant homology to cyclin proteins in other organisms. Northern blot analysis indicated that the cDNA corresponded to a low-abundance mRNA (approximately 0.001% of poly(A)+RNA). Southern blot analysis indicated that genes encoding this mRNA were discontinuously distributed in this fungal species, indicating it encodes a dispensable function. This result suggests that natural populations of fungi may have variable complements of cyclin-encoding genes.