Identification and characterization of a novel gene, TrCCD1, and its possible function in hyphal growth and...

To investigate genes with essential functions during hyphal growth or sporulation in the asexual filamentous fungus Trichoderma reesei, we screened a collection of T-DNA insertion mutants and identified the genomic integration events. Two mutants with abnormal phenotypes, named as ccdO and ccdP, were found to have independent T-DNA insertions into a putative TrCCD1 gene locus, the product of which has significant homology to carotenoid cleavage dioxygenases (CCDs). Compared to the parental strain, both mutants tended to produce slow-growing hyphae and had a more than 50% reduction in colony growth rate. Simultaneously, the hyphae of the growing mutants formed wilting tip while the parental strain elongated straightly. To the effect of the TrCCD1 mutation on the conidiospore development, less spores were formed in the mutants than in the parental strain. In addition, disruption of TrCCD1 resulted in another phenotype characterized by a remarkable enhancement in the total carotenoid content. When the wild-type TrCCD1 gene was reintroduced into the ccd mutants, the abnormal phenotypes were rescued. These results suggest that TrCCD1 is involved in carotenoid metabolism and likely required for hyphal growth and conidiospore development in filamentous fungi T. reesei.