Difterential CAZyme Genes Expression Of Homo-and Hetero-Karyon Of The Straw-Degrading Mushroom Volvariella Volvacea Identified By3'-tag Digital Gene Expression Profiling

Volvariella volvacea (Bull.: Fr.) Singer, the Chinese straw mushroom, is astraw-degrading basidomycete fungus that is an important edible fungus of the tropicsand subtropics. Due to its cellulolytic characteristics, V. volvacea had been cultivatedon an array of agro-industrial residues. But low biological efficiency (i.e. conversionof growth substrate into mushroom fruiting bodies) has limited its production onlignocellulosic wastes. In this study, we report the3'-tag digital gene expression(DGE) of the two monokaryotic V. volvacea strains PYd15and PYd21and aheterokaryotic strain H1521which is a hybird strain of PYd15and PYd21. With thesupport of genome and transcriptome sequencing data of V. volvacea, we have studiedCAZymes families and gene subfamilies (cellulose, hemicellulose and pectindegradation) of V. volvacea and analysed the comparison of the number of CAZymesin V. volvacea with those in other11biomass-degrading fungi genomes. And on thebasis of DGE, we detected and analysed the differential CAZymes gene expression ofhomo-and hetero-karyon of V. volvacea to reveal how the differential expression ofgenes encoding Carbohydrate-active enzymes (CAZymes) impacts the biologicalefficiency of V. volvacea.The Carbohydrate-Active Enzyme database (CAZy) identified192glycosidehydrolases (GH),44glycosyl transferases (GT),19polysaccharide lyases (PL) and31carbohydrate esterases (CE) encoded in the genome of V. volvacea. It is demonstratedthat the size of CAZyme families of V. volvcea is larger than those of most otherbiomass-degrading fungi. Among12biomass-degrading fungi genomes used in thisstudy, V. volvacea has the forth large CAZyme families' size, just smaller than that ofAspergillus nidulans,Schizophyllum commune and Coprinopsis cinerea. Comparedto the genomes of other basidiomycetes, V. volvacea has higher number of GH,PLand CE than the average number of those found in this lineage (161,8,24,respectively). But the number of GT in V. volvacea is slightly below the averagenumber of GT found in this lineage (65). V. volvacea is rich in genes encoding enzymes that degrade pectin, hemicellulose and cellulose. In fact, V. volvacea has thehighest number of genes involved in the degradation of these plant cell wallpolysaccharides among the basidiomycetes we analyzed. The V. volvacea genome isparticularly rich in members of the glycosyl hydrolase families GH10(hemicellulosedegradation) and GH43(hemicellulose and pectin degradation), and the lyase familiesPL1, PL3and PL4(pectin degradation).Using DGE, we compared whole-genome expression of the three strains PYd21,PYd15and H1521. Of the30,845reference genes,54.47%are expressed in at leastone strain. Whereas fewer of the unique expressed genes of every strain, in this study,were observed, suggesting that the genes only expressed in one strain of V. volvaceawere more stringently regulated. To identify global transcriptional changes in thethree strains,6465genes were declared to be differentially expressed between thehomo-and hetero-karyon. Among the three V. volvacea strains which have beensequenced using DGE technology, there are246genes encoding CAZymes expressedin at least one strain. Of these genes,177are expressed in all the three strains.21genes of H1521encoding CAZymes are up-regulated compared with PYd15, and40genes of H1521encoding CAZymes are up-regulated compared with PYd21. It isdemonstrated that heterokaryon strains of V. volvacea has obviously predominantcapacity to degrade biomass, compared with homokaryon strains of V. volvacea.Here, We compared CAZyme families and gene subsets (cellulose, hemicelluloseand pectin degradation) with the corresponding gene subsets from11biomass-degrading fungi for which genome sequences are available, including V. volvacea.And high-throughput sequencing and bioinformatics were utilized to analyze therelationship between gene expression profile and haploid homo-and hetero-karyon.Futher to study the CAZymes of V. volvacea and to reveal the differential expressionof genes encoding CAZymes between the three V. volvacea strains. Gain some insightinto the CAZymes families and the capacity to degrade biomass in V. volvacea, withthe support of genome sequence and transcriptome.