Research On The Enzymes Activities And Gene Expression Of Hemicellulase In Volvariella Volvacea

Volvariella volvacea is one of important grass-rot fungi which grow in the environment of high humidity and temperature. Volvariella volvacea uses the crop straw riched in cellulose and hemicellulase as the growth substrate. Straw mushroom can secrete hemicellulase to provide the nutrients needed for growth through degradating hemicellulose. But Volvariella volvacea shows a low biological transformation efficiency with only 10-40% compared to other edible mushrooms, such as Agaricus bisporus shows biological efficiency up to 80-100%. The hemicellulose degradation mechanism of Volvariella volvacea is very complex. We study the hemicellulase genes expression and cellulase activity in straw mushroom, and try to find the relationship among the hemicellulose degrading enzyme gene, enzyme activity and biological transformation efficiency. The results may help to improve the biological transformation efficiency of Volvariella volvacea and have benefits for straw mushroom industry.In previous studies, the whole-genome sequencing project of Volvariella volvacea had been completed, and the genome-wide framework map had been established. Based on these results, we find out the gene encoding hemicellulase degrading enzymes by bioinformatics analysis. Hemicellulase degrading enzymes structure between grass-rotting fungi and wood-rotting fungi were compared and try to explore the reasons for the low biological transformation efficiency.1. There are 17 straw mushroom strains used for fruiting experiment. Through calculating the biological transformation efficiency,17 strains were divided into 9 categories through significant analysis:First, Pinyouyihao; Second, Vn-1, Z-VH3; Third, Vn-3,0229, V23; Fourth, VH3, TaiguoNO.1, WG, Vbl; Fifth, Z-VH3, Dagutuo34, Tuo31, A8; Sixth, Siliancaogu No.4,427-434; Seventh,3560. There are no significant differences of biological transformation efficiency in internal strains of each type, but there are significant differences between classes. The strain Pinyouyihao has the highest biological efficiency of 21.73%, while 3560 has the lowest biological efficiency of 1.95%. Three strains of high, medium and low biological transformation efficiency are sampled for study the enzyme activity and gene expression.2. The results of the phylogenetic tree show that XynⅡ and Xy1 are similar with those in wood-rotting fungus. Xyn1, α-L-arabinofuranosidase, α-glucosiduronase, acetylxylan esterase in Volvariella volvacea are far apart from those in wood-rotting fungus. According to this research, we suggest that some correlation may exist between the hemicellulose degradation ability and genetic differences.3. The xylanase activity in 0229 is significantly higher than that in Vb1, while A8 is the least. It is significantly different between xylanase activity in Volvariella volvacea 0229、Vb1 and A8. Xylosidase activity in Vb1 is highest. There is no significantly different between xylosidase activity in Volvariella volvacea 0229 and A8. It is indicated that cellulase activity may be positive correlated with biological efficiency in Volvariella volvacea, suggesting that xylanase is crucial.4. For gene expression, xynⅡ expression in Vb1 is lower than in 0229, A8 is lower than that in Vb1. There is some correlation between the hemicellulose degradation ability and genetic differences. The secretion of xylanase maybe different at transcriptional level, suggesting that xynⅡ is more important than others. The xyl expression in Vb1 is highest. in 0229 and A8 simliar. We speculate that the activity and secretion of xylosidase are regulated by xyl expression level.