PNNL

Abstract

The filamentous fungus Trichoderma reesei is predominantly found in the tropics, but also in more temperate regions, such as Europe and is widely known as producer of high amounts of plant cell wall degrading enzymes. We sequenced the genome of the sexually competent isolate CBS999.97, which is phenotypically different from female sterile QM6a, but can cross sexually with QM6a. Transcriptome data for growth on cellulose showed that entire CAZyme families are consistently differentially regulated between these strains. We evaluated backcrossed strains of both mating types, which acquired female fertility from CBS999.97, but maintained a mostly QM6a genetic background and could thereby distinguish between effects of strain background and female fertility or mating type. We found clear regulatory differences associated with female fertility and female sterility, that included CAZyme and transporter genes. Analysis of carbon source utilization, transcriptome and secondary metabolites in these strains revealed that only a few changes in gene regulation are consistently correlated with different mating types. Different strain backgrounds (QM6a versus CBS999.97) resulted in the most significant alterations in the transcriptome and in carbon source utilization, with decreased growth of CBS999.97 on several amino acids (for example proline or alanine) which further correlated with down-regulation of genes involved in the respective pathways. In combination, our findings support a role of fertility associated processes in physiology and gene regulation and are of high relevance for the use of sexual crossing in combining characteristics of two compatible strains or QTL analysis.