Sulyok M, Schmoll M, Böhmdorfer S, Hsu PW, Tisch D, Schuster A, Baker SE, Dattenböck C, Chuang YC, Chen CL, Pomraning KR, Wang TF, Collett JR, Freitag M, Oberlerchner J, Stappler E
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.ImportanceTrichoderma reesei is a filamentous fungus with a high potential for secretion of plant cell wall degrading enzymes. We sequenced the genome of the fully fertile field isolate CBS999.97 and analyzed its gene regulation characteristics in comparison with the commonly used lab-wildtype QM6a, which is not female fertile. Additionally, we also evaluated fully fertile strains with a genotype very close to QM6a in order to distinguish between strain specific and fertility specific characteristics. We found that QM6a and CBS999.97 clearly differ in growth patterns on different carbon sources, CAZyme gene regulation and secondary metabolism. Importantly, we found altered regulation of 90 genes associated with female fertility including CAZyme genes and transporter genes, but only minor mating type dependent differences. Hence, when using sexual crossing in research and for strain improvement it is important to consider female fertile and female sterile strains for comparison with QM6a and to achieve optimal performance.
