Molecular and biochemical studies on cellulose synthase (OsCesA10) and root proteins from rice (Oryza sativa L.) under drought condition

Cellulose biosynthesis is important in drought tolerance, and a major candidate gene associated with cellulose biosynthesis, cellulose synthase 10 (OsCesA10) was studied. In silico analysis revealed that the promoter sequence of OsCesA10 has cis-acting elements associated with drought response and the OsCesA10 protein is transiently present in the ER, due to its hydrophobic character near the N-terminus and the absence of the KDEL signal. The OsCesA10 protein also possesses domains for both cellulose synthase and family 2 glycosyltransferase activities. Molecular analyses based on PCR and Southern hybridization revealed that OsCesA10 is present in Way Rarem and +QTL lines but absent in Vandana and -QTL lines. Cloning of OsCesA10 showed that Way Rarem, +83, and +21 were 100% similar, while the Way Rarem and the +QTLs were 99% similar with Nipponbare. The data from the quantitative PCR id not give any conclusive result as to whether OsCesA10 is upregulated under drought. Phenotype analysis by microscopy showed that +QTL lines have more cellulose than -QTL lines. Cellulose quantification by spectrophotometry showed that under drought stress there was a significant difference in the cellulose content of Way Rarem compared with +QTL and -QTL lines. After extraction of leaf and root proteins by Tris-HCl buffer, degradation of the leaf proteins by the root proteases in the leaf + root protein extracts from rice was shown to be inhibited by boiling of the leaf + root proteins after extraction, possibly due to inactivation of root proteases by boiling. The results of in silico data mining, genotypic and phenotypic characterization all implicate a role for OsCesA10 through affecting root hair proliferation towards drought tolerance. However, OsCesA10 by itself may not be sufficient for drought tolerance or root hair proliferation. Additional strong candidate genes may act in concert with OsCesA10 for the functionality of the rice chromosome 12 -QTL12.1 region. Additional expression analysis at the transcript and protein levels and silencing and over-expression of transgenic rice plant lines will confirm this direct relationship.