Transcriptomic profiles of Heterobasidion annosum under abiotic stresses and during saprotrophic growth in bark, sapwood and heartwood.

The success of many wood decaying fungi lies in their ability to overcome unfavourable environmental conditions within and outside of litter and wood debris. Although so much has been learned about the ecology, taxonomy and physiology of several wood decaying basidiomycete fungi, the molecular basis for their survival in a diverse range of substrates and ecological habitats has been very little studied. Using the wood decay fungus (Heterobasidion annosum s.s.) as a model, we investigated its transcriptomic response when exposed to several environmental stressors (high and low temperature, osmotic stress, oxidative stress and nutrient starvation) and during growth on specific pine wood compartments (bark, sapwood and heartwood). Among other genes and pathways, we documented the specific induction of the major facilitator superfamily 1 and cytochrome P450 families at low temperature, and protein kinases together with transcription factors during starvation. On the other hand, during saprotrophic growth, we observed the induction of many glycosyl hydrolases, three multi-copper oxidases (MCO), five manganese peroxidases (MnP) and one oxidoreductase which are specific for wood degradation. This is the first study providing insights on the potential mechanisms for adaptation to abiotic stresses and pine heartwood degradation in H. annosum s.s.