SINGLE MATING TYPE-SPECIFIC GENES AND THEIR 3'-UTRS CONTROL MATING AND FERTILITY IN COCHLIOBOLUS-HETEROSTROPHUS

To determine the number of proteins required for mating type (MAT) loc us-regulated control of mating in Cochliobolus heterostrophus, MAT fra gments of various sizes were expressed in MAT deletion strains. As lit tle as 1.5 kb of MAT sequence, encoding a single unique protein in eac h mating type (MAT-1 and MAT-2), conferred mating ability, although an additional 160 bp of 3' UTR was needed for production of ascospores. No other mating type-specific genes involved in mating identity or fer tility were found. Thus, although homologs of the C. hererostrophus MA T-I and MAT-2 genes exist in the filamentous ascomycetes Neurospora cr assa and Podospora anserina, C. heterostrophus does not appear to have mating type-specific homologs of two additional genes required by bot h N. crassa and P. anserina for successful sexual reproduction. Three genes were identified in the common DNA flanking the MAT locus: a gene encoding a GTPase-activating protein and an ORF of unknown function l ie 5' while a beta-glucosidase encoding gene lies found 3'. None of th ese genes appears to be involving in the mating process.