Looking for REX (looking for Phanerochaete chrysosporium mutants Resistant to EXtractives)

PI : Rodnay Sormani (UMR 1136 Interactions ARbres/Micro-organismes – IAM)

Co-applicants : Stéphane Dumarçay (Laboratoire d’Etudes et de Recherche sur le Matériau Bois – LERMAB)


Context — The interest for wood decaying fungi has increased in the last few years mainly because of their potential use in biomass valorization, of their function in global carbon cycle and of the damages that they can cause on wood material. Indeed, these fungi are efficient organisms for the degradation and use of cellulose and hemicelluloses as carbon and energy sources. However, the oxidative processes used by these fungi to decompose wood generates a myriad of potential toxic molecules including extractives. Extractives are non structural components of wood that are responsible for wood properties such as color and durability. To adapt to that toxic environment, wood decaying fungi have developed various detoxification strategies. Genomic studies have highlighted some gene families coding for detoxification systems in wood decaying fungi, but still the general lack of physiological data concerning detoxification pathways is mainly due to the absence of available genetic tools for these organisms.

Objectives — Phanerochaete chrysosporium is a wood decaying fungus able to degrade all components of wood. The efficiency of degradation to decompose both cellulose and lignin is not only based on the extracellular enzymatic system but also to the ability of the fungus to cope with the extractives. The aim of this work is to decipher the ability of this fungus to cope with toxic molecules.

Approaches — To investigate the response of P. chrysosporium to the toxicity of wood extractives without a priori, we propose to perform a forward genetic strategy to identify genes involved in the resistance/detoxification process developed by the fungus. We propose to generate a UV mutant library of P. chrysosporium and screen extractive-resistant strains (rex mutants) using a lethal concentration of extractives.

Expected results and impacts — The characterization of the identified mutants and the analysis of their genome will allow us to identify the systems allowing fungi to cope with the toxic extractives during wood degradation.