Feed or fight - light, nutrients and toxins in fungi

In their natural habitat, fungi constantly face the challenge to outcompete other organisms in complex ecosystems. Therefore they developed powerful enzyme systems for degradation of substrate, which provide for fast growth and efficient colonization of their environment. However, also their ability to produce toxic chemicals (secondary metabolites) serves as defense against competitors. Our studies with Trichoderma reesei (Hypocrea jecorina), a model organism for investigation of plant cell wall degradation and the interplay between light response and metabolism, revealed a light regulated secondary metabolite gene cluster. Transcription of the genes of this cluster is repressed by the photoreceptors BLR1 and BLR2 in light. In darkness, however, this cluster is regulated by the carbon catabolite repressor CRE1 and the cAMP pathway component protein kinase A (PKA). Consequently, a tightly regulated mechanism for balancing resources for nutrient acquisition (feed) and biosynthesis of secondary metabolites (fight) appears to be operative and its effect is dependent on light. In the course of the proposed project we intend to evaluate this hypothesis. We will investigate the light dependent posttranslational regulation and function of CRE1, as well as its assumed direct or indirect interplay with the photoreceptor BLR1. Metabolomic analyses will complement these studies and reveal the secondary metabolite profile of T. reesei as well as the structure of the secondary metabolite produced by the two polyketide synthetases as central components. In order to understand secondary metabolite production in T. reesei, the influence of light and CRE1 on this process in T. reesei in general shall be studied. Therefore we will investigate the function of CRE1 in chromatin rearrangement, which is already known from cellulase regulation, in a broader context also considering the involvement of photoreceptors. Paralleling the studies on secondary metabolism, we will also survey cellulase gene expression as a model output pathway for nutrient degradation throughout the project. This strategy will allow us to put substrate degradation and secondary metabolism in context and thereby gain intriguing new insights into the balance of investing resources in growth or fending off competitors during the life of a fungus.

No additional funding sources recorded.