Inactivation of a P leurotus ostreatus versatile peroxidase‐encoding gene ( mnp2 ) results in reduced lignin degradation

Abstract

Summary Lignin biodegradation by white‐rot fungi is pivotal to the earth's carbon cycle. Manganese peroxidases ( MnP s), the most common extracellular ligninolytic peroxidases produced by white‐rot fungi, are considered key in ligninolysis. P leurotus ostreatus , the oyster mushroom, is a preferential lignin degrader occupying niches rich in lignocellulose such as decaying trees. Here, we provide direct, genetically based proof for the functional significance of MnP to P . ostreatus ligninolytic capacity under conditions mimicking its natural habitat. When grown on a natural lignocellulosic substrate of cotton stalks under solid‐state culture conditions, gene and isoenzyme expression profiles of its short MnP and versatile peroxidase ( VP )‐encoding gene family revealed that mnp2 was predominately expressed. mnp2 , encoding the versatile short MnP isoenzyme 2 was disrupted. Inactivation of mnp2 resulted in three interrelated phenotypes, relative to the wild‐type strain: (i) reduction of 14% and 36% in lignin mineralization of stalks non‐amended and amended with M n 2+ , respectively; (ii) marked reduction of the bioconverted lignocellulose sensitivity to subsequent bacterial hydrolyses; and (iii) decrease in fungal respiration rate. These results may serve as the basis to clarify the roles of the various types of fungal MnP s and VPs in their contribution to white‐rot decay of wood and lignocellulose in various ecosystems.

Bibliographic Information