Email updates

Keep up to date with the latest news and content from BMC Genomics and BioMed Central.

Open Access Highly Accessed Research article

Targets of light signalling in Trichoderma reesei

Doris Tisch1 and Monika Schmoll2*

Author Affiliations

1 Research Area of Gene Technology and Applied Biochemistry, Institute for Chemical Engineering, Vienna University of Technology, Gumpendorferstraße 1a, Wien A-1060, Austria

2 Department Health and Environment – Bioresources, AIT Austrian Institute of Technology, Konrad-Lorenz Strasse 24, Tulln 3430, Austria

For all author emails, please log on.

BMC Genomics 2013, 14:657  doi:10.1186/1471-2164-14-657

Published: 26 September 2013

Abstract

Background

The tropical ascomycete Trichoderma reesei (Hypocrea jecorina) represents one of the most efficient plant cell wall degraders. Regulation of the enzymes required for this process is affected by nutritional signals as well as other environmental signals including light.

Results

Our transcriptome analysis of strains lacking the photoreceptors BLR1 and BLR2 as well as ENV1 revealed a considerable increase in the number of genes showing significantly different transcript levels in light and darkness compared to wild-type. We show that members of all glycoside hydrolase families can be subject to light dependent regulation, hence confirming nutrient utilization including plant cell wall degradation as a major output pathway of light signalling. In contrast to N. crassa, photoreceptor mediated regulation of carbon metabolism in T. reesei occurs primarily by BLR1 and BLR2 via their positive effect on induction of env1 transcription, rather than by a presumed negative effect of ENV1 on the function of the BLR complex. Nevertheless, genes consistently regulated by photoreceptors in N. crassa and T. reesei are significantly enriched in carbon metabolic functions. Hence, different regulatory mechanisms are operative in these two fungi, while the light dependent regulation of plant cell wall degradation appears to be conserved.

Analysis of growth on different carbon sources revealed that the oxidoreductive D-galactose and pentose catabolism is influenced by light and ENV1. Transcriptional regulation of the target enzymes in these pathways is enhanced by light and influenced by ENV1, BLR1 and/or BLR2. Additionally we detected an ENV1-regulated genomic cluster of 9 genes including the D-mannitol dehydrogenase gene lxr1, with two genes of this cluster showing consistent regulation in N. crassa.

Conclusions

We show that one major output pathway of light signalling in Trichoderma reesei is regulation of glycoside hydrolase genes and the degradation of hemicellulose building blocks. Targets of ENV1 and BLR1/BLR2 are for the most part distinct and indicate individual functions for ENV1 and the BLR complex besides their postulated regulatory interrelationship.

Keywords:
Trichoderma reesei; Hypocrea jecorina; Light response; Glycoside hydrolases; D-galactose; L-arabinose; ENVOY; BLR1; BLR2