The Phylogenetic And Function Analysis Of Cellulase Gene Families In Sugarcane

Sugarcane belongs to the grass family (Poaceae), is an economically improtant seed plant with highest biomass among the crops. Sugarcane bagasse is a potentially abundant source of energy with main compotent of cellulose. The cellulase plays key role for cellulose accumation in plant. However, in sugarcane, very limited information for its molecular study is available so far. In this study, aim to investigate the molecular basis for the gene involving in cellulose accumlation, we identified the cellulase gene families by comparative genomics and explored the gene function by using model plant Arabidopsis.Based on comparative genomices study,73 members of 7 families for cellulase gene were predicted to exist in sorghum, of them,24 were indentified and sequenced from Saccharum spontaneum BAC library. Phylogenetic analysis showed that 7 family in separate branch in evolutionary tree, suggesting distinct divergence for their functions. The sequences comparison between sorghum and sugarcane demonstrate that the gene families shared high homology above 90%. Futhermore, GH9A and GH9C in the GH9 subfamilies were observed to keep more stable gene structure with slower evolutionary rate, indicating the two subfamilies were the major funcational gene among the family, In addition, GH9B subfamily contained more members, large difference of gene structure and low evolutionary rate, which guggested that potential gene functional redundancy existed in the family.The gene express profile were investigated by using RNA-seq with RPKM analysis and great variation of gene expression level among celllulase gene famlies were observed in Saccharum species, S.spontaneum, Saccharum robustum, Saccharum officinarum. Of the gene in the family,6 high-expressed genes presented very abundant expression level with ScGH9A3 ranked as the top, and 9 medium-expressed genes were espressed in most of tissues, while, the rest genes were low express and absented in most of tissues. Also, the high-expressed genes mainly expressed in tender parts and was sensitive to the drought stress. Under draught stress, the gene was down-regulated expression besides ScGH47-4. Among the three Saccharum species, S.officinarum had most number of cellulose genes, while S.spontenum had the least gene number reponsing to drought stress.Arabidopsis mutants was used to explore the functions of sugarcane cellulase gene. Based on the phenotype of T-DNA insertion Arabidopsis mutant, AtGH9B8 was observed to played a role in cellulose synthesis, AtGH9B3, AtGH9B19,AtGH9B4 and AtGH9B18 involvedin cellulose hydrolyzation. The functions of cellulase gene family members could interact with each other both synergistically or antagonistically. Secondly, we cloned 10 cellulase cDNA from sugarcane, and 5 cellulase genes and 13 promoters from Arabidopsis.We constructed ScGH9A3, ScGH9B16, ScGH9B5, ScGH9B14 plant expression vectors and will transfer to Arabidopsis mutants for further sugarcane cellulase gene function analysis.