Differential expression patterns reveal the roles of cellulose synthase genes (CesAs) in primary and secondary cell wall biosynthesis in Miscanthus x giganteus

The second-generation biofuels utilizing the cellulose from non-food lignocellulosic biomass feedstocks are renewable, environmentally friendly, not in competition with food and have the potential to tackle global energy crisis. Miscanthus x giganteus, a promising lignocellulosic energy crop with advantages of vigorous growth, high biomass yield, and potential for using marginal lands has attracted the interest of researchers. However, the high cost of feedstock (similar to 39 % of the total) limits the selling price and consequent competitiveness of the ethanol produced from M. x giganteus. To cross the obstacle, lowering down the cost by improving the production and properties of cellulosic biomass thus becomes an import topic. In higher plants, CesA genes encode glycosyl-transferases that play key roles in the cellulose biosynthesis. To achieve higher yield and better efficient utilization of biomass in M. x giganteus, more knowledge on the function of each CesA in cellulose biosynthesis is urgent. In this study, the transcription of at least ten CesA genes was detected in M. x giganteus (MgCesAs). Among these, six full-length MgCesA genes were cloned. The functions of the MgCesAs were inferred based on their phylogenetic relationships and differential expression patterns. Specifically, MgCesA10, 11, 12 are likely involved in the secondary cell wall biosynthesis and form a cellulose synthase complex (CSC) with a ratio of 1:1:1. While MgCesA5, 6, which are constitutively expressed in all organs, together with MgCesA2, 3, 4, 7 and 8 tend to participate in the primary cell wall biosynthesis of M. x giganteus. This study not only lays a foundation for understanding the biosynthesis of cellulose and further functional analyses of CesAs in M. x giganteus, but also sheds light on future improving of the production and properties of cellulosic biomass in M. x giganteus.