Genomic and transcriptomic analyses of the basidiomycete Irpex lacteus CD2 reveal unique enzymatic mechanisms in lignocellulose degradation


Xing Qin;Xiaoyun Su;


The white rot basidiomycete fungus Irpex lacteus is potent in degrading lignocellulose;however,the molecular mechanism involved is poorly understood.An I.lacteus CD2 strain was isolated from Shennong Natural Reserve,Hubei Province,China.One homokaryon derivative of CD2 was isolated and sequenced by the PacBio sequencing technology to obtain a genome of 43 Mb.The genome of CD2 encodes an impressive number of peroxidases,oxidoreductase and hydrolytic enzymes that are supposed to cooperate in lignocellulose degradation.Among these enzymes,CD2 possesses a remarkable enzyme arsenal for lignin breakdown including manganese peroxidases(MnPs),lignin peroxidases(LiPs)and dye-decolorizing peroxidases(DyPs),which is a newly identified heme peroxidase family.Ligninolytic enzymes,but not cellulolytic and xylanolytic enzymes,were highly expressed on day 3 post culture on corn stover at the transcript and protein levels.With the time going on,cellulases and xylanases gradually increased with the lignin-degrading enzymes diminished.The enzymatic profile over time is suggestive of a mechanism involved successive degradation of cellulose,xylan,and lignins by I.lacteus.In addition,our transcriptomic analysis also indicated that the oxidative enzymatic system including peroxidases,oxidoreductase and reactive oxygen species such as hydroxyl radicals,peroxyl radicals and hydroperoxyl radicals,are involved in lignin depolymerization by I.lacteus.Further comparative genomic analysis with other white rots will allow us to gain more insights into how lignocellulose is degraded by this organism.And functional genomics studies are under way for candidate regulatory genes involved in lignocellulose degradation by I.lacteus.




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