Molecular characterization of a cellulose synthase gene (AaxmCesA1) isolated from an Acacia auriculiformis x Acacia mangium hybrid

Cellulose is the major component of plant cell walls, providing mechanical strength to the structural framework of plants. In association with lignin, hemicellulose, protein and pectin, cellulose forms the strong yet flexible bio-composite tissue of wood. Wood formation is an essential biological process and is of significant importance to the cellulosic private sector industry. Cellulose synthase genes encode the catalytic subunits of a large protein complex responsible for the biogenesis of cellulose in higher plants. The hybrid Acacia auriculiformis x Acacia mangium represents an important source of tree cellulose for forest-based product manufacturing, with enormous economic potential. In this work, we isolate the first cellulose synthase gene, designated AaxmCesA1, from this species. The isolated full-length AaxmCesA1 cDNA encodes a polypeptide of 1,064 amino acids. Sequence analyses revealed that AaxmCesA1 cDNA possesses the key motif characteristics of a CesA protein. AaxmCesA1 shares more than 75 % amino acid sequence identity with CesA proteins from other plant species. Subsequently, the full-length AaxmCesA1 gene of 7,389 bp with partial regulatory and 13 intron regions was also isolated. Relative gene expression analysis by quantitative PCR in different tissues of the Acacia hybrid, suggests the involvement of the AaxmCesA1 gene in primary cell wall synthesis of rapidly dividing young root cells. Similarity analyses using Blast algorithms also suggests a role in primary cell wall deposition in the Acacia hybrid. Southern analysis predicts that AaxmCesA1 is a member of a multigene family with at least two isoforms in the genome of the Acacia hybrid.