Molecular cloning and characterization of two differentially expressed Cellulose synthase gene isoforms in Leucaena leucocephala: A pulp yielding tree species

Leucaena leucocephala is fast growing leguminous tree species, acclimatized to variety of soil and climatic conditions. It is widely used for pulp production in India. Pulp mainly consists of cellulose, which is a simple polymer of unbranched β-1, 4-linked glucan chains. The polymerization of glucose residues into a β-1, 4-linked backbone is catalysed by the enzyme cellulose synthase (CesA). Here, cDNAs encoding CesA genes from Leucaena were isolated and characterized. The two complete cDNAs of 3.228 kb and 3.222 kb encoding CesA gene from L. leucocephala were designated as Ll-7CesA (FJ871987) and Ll-8CesA (GQ267555) respectively. In-silico studies showed that Ll-7CesA has 95.2% identities and Ll- 8CesA has 95.8% identities with Acacia mangium CesA2. Phylogenetic analysis revealed significant similarity with known dicot CesA genes. The deduced amino acid sequence of both CesA genes contained the conserved D, D, D, QxxRW motif, eight membrane spanning regions and a putative zinc binding domain, which are characteristic of glycosyltransferases. DNA blot analysis suggested, CesA gene to be in multiple copies in Leucaena genome. Semi quantitative and quantitative real-time PCR expression analysis of Ll-7CesA gene showed more expression in stem than leaf and not detected in root where as Ll-8CesA gene was expressed more in stem than leaf and root. Overall Ll-8CesA was expressed in all tested tissues and could be involved in active cellulose biosynthesis.