3.2 Genes related to biodegradation in G.lucidum
Aside from its medicinal and economic value，limited studies focused on the biodegradation function of G.lucidum so far.JGIsequenced its genome because of its ability in wood degradation and potential value in bio-energy production.In our analysis，we found that many genes might be involved in biodegradation in G.lucidum genome.G.lucidum could degrade the major components of plant cell walls including cellulose，hemicelluloses and lignin.After predicted the CAZymes in G.lucidum，199 putative Glycoside Hydrolase(GH)genes and 79 putative Glycosyl Transferase(GT)genes were found.While the number of GHs was comparatively larger than GTs，it is maybe related to its lifestyle that it survived dependent upon decomposing lignocellulose，thus decomposing polysaccharides is more important than constructing.The same phenomenon is also observed in P.chrysosporium［26］.
Lignin is the second most abundant renewable organic polymer and its degradation has great potential value to reproductive energy.Thus the research about lignin degradation especially in white rot fungi is increasing.We checked the FOLymes enzymes in G.lucidum and found that it had 15 laccase(LO1)，7 peroxidases(LO2)and 10 glyoxal oxidases(LDA3)genes.Laccase is one of the most applied ligninolytic enzymes，for its broad substrate specificity and the generation of water as by-product［34］.However，we found no laccase genes in the lignin-degrading fungus P.chrysosporium and more than 10 laccase genes in two fungi(C.cinerea and L.bicolor)，which may be poorly efficient degradation of lignocellulose.It seems that laccase was unessential for wood and lignin decomposition and it might involve in other function，such as pigments synthesis，fruiting bodies and spores formation［35］.Makela et al.found multiple lip，mnp and lac transcripts are coexpressed in P.radiate and indicated the potential synergy of the fungal heme peroxidases and laccases upon white rot fungal decay of wood［36］.(https://www.daowen.com)
Peroxidases(LO2)mainly existed in white rot and wood-colonising basidiomycetes(P.chrysosporium，P.ostreatus，and G.lucidum).This suggested LO2 played important roles in the decomposition of lignin.It has been reported that glyoxal oxidases(LDA3)were inactive unless they coupled to the peroxidase reaction［37］.Here，we identified 10 glyoxal oxidases in the G.lucidum.Considering the total number of LO2 and LDA3 genes in all the fungi we analyzed，P.ostreatus(25 genes)and P.chrysosporium(23 genes)were the top two fungi which are reported with strong ligninolytic ability.G.lucidum had the third largest number of LO2 and LDA3 genes(17 genes)，which might suggest its strong ligninolytic ability.In addition，in G.lucidum we also found one LDA1 gene，which could reduce the radical compounds and quinonoids produced by laccase(LO1)，may form an oxidative enzyme system with laccase(LO1)［38］.
Moreover，G.lucidum showed rich P450 family，abundant GST enzymes(mainly Omega class)and abundant genes involved in“Xenobiotics Biodegradation and Metabolism”pathways.Some of these pathways are related to the degradation of refractory compounds，such as dioxin and naphthalene.These enzymes have potential to degrade various industrial pollutants［39］.In view of the extensive contamination of the environment by persistent and toxic chemical pollutants，the utility of the degradation of fungi including G.lucidum may be an attractive and effective approach on pollution controlling.