title: Inactivation of a Pleurotus ostreatus versatile peroxidase-encoding gene (mnp2) results in reduced lignin degradation.
abstract: Lignin biodegradation by white-rot fungi is pivotal to the earth's carbon cycle. Manganese peroxidases (MnPs), the most common extracellular ligninolytic peroxidases produced by white-rot fungi, are considered key in ligninolysis. Pleurotus 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 Mn(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 MnPs and VPs in their contribution to white-rot decay of wood and lignocellulose in various ecosystems.
authors.affiliation: Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 76100, Israel.
authors.forename: Tomer M
authors.initials: TM
authors.lastname: Salame
authors.forename: Doriv
authors.initials: D
authors.lastname: Knop
authors.forename: Dana
authors.initials: D
authors.lastname: Levinson
authors.forename: Sameer J
authors.initials: SJ
authors.lastname: Mabjeesh
authors.forename: Oded
authors.initials: O
authors.lastname: Yarden
authors.forename: Yitzhak
authors.initials: Y
authors.lastname: Hadar
mesh_terms: D000595:Amino Acid Sequence; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D020868:Gene Silencing; D008031:Lignin / Q000378:metabolism*; D008969:Molecular Sequence Data; D010544:Peroxidases / Q000235:genetics* / Q000378:metabolism; D020076:Pleurotus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D014934:Wood / Q000378:metabolism / Q000382:microbiology*
chemical_list: D005656:Fungal Proteins; C036909:lignocellulose; D008031:Lignin; D010544:Peroxidases; C051129:manganese peroxidase