Abstract: [Objective] Acacia mangium is widely cultivated in southern China for paper production. Cellulose synthase (CesA) plays a vital role in the synthesis of cellulose, which is an important factor in controlling the quality and yield of wood fiber. In this study, we cloned a cellulose synthase gene of A.mangium, and studied its response to hormones to help the understanding of the synthesis of cellulose and the high fiber yield of A.mangium.[Method] A CesA was obtained from A.mangium seedlings by RT-PCR and RACE, named AmCesA1 (AY643519). The gene was analyzed by bioinformatics software. The copy form of the gene was determined through using Southern analysis.The expression level of the gene in different tissues and the expression of gibberellin,6-BA and methyl jasmonate were determined by real-time fluorescence quantitative PCR.[Result] The molecular size of AmCesA1 is 3 793 bp, and its ORF is 3 249 bp,suggesting that this gene encodes 1 082 amino acids.Protein molecular formula is C₅₄₉₅H₈₄₉₁N₁₄₅₇O₁₅₇₉S₅₀. The number of positive charge amino acid residues (Arg + Lys) is 121, and the number of negative charge amino acid residues (Asp + Glu) is 125. The isoelectric point is 6.51, which means that it is acidic protein. Its instability coefficient is 40.82, belonging to the unstable protein. The amino acid primary structure analysis of AmCesA1 showed that it had the conserved D, D, D and QxxRW functional domains of cellulose synthase, and had a unique P-CR region and the HVR region and N-terminal zinc finger structure. There were six transmembrane regions at the C-terminus, but the two transmembrane regions at the N-terminus were not significant. Secondary structure analysis showed that it had more α-helix, random coil, but fewer β-turn, while β-sheet number varies greatly due to the different algorithms. Cluster analysis showed that AmCesA1 had similarity with Glycine max GmCesA1 and Arachis duranensis AdCesA1.But it did not appear to be close to the results of woody plants. Further comparison with Arabidopsis thaliana cellulose gene family amino acid sequence indicated a fact that AmCesA1 was similar to AtCesA1 and AtCesA10 in A.thaliana, and its similarity was 86% and 80%, suggesting that it had the same function as A.thaliana AtCesA1 and AtCesA10.Southern analysis showed that AmCesA1 was present in multiple copies of the Acacia tree genome. Real-time quantitative PCR showed that AmCesA1 was widely expressed in roots, stems and leaves, and the differences among them were not significant. AmCesA1 had a response to GA₃, 6-BA and MeJA treatments, in which the response to GA₃ was relatively strong.[Conclusion] AmCesA1 cloned in this study is a member of the plant CesA family, presumably involved in the formation of primary cell walls. The gene was responsive to gibberellin, 6-BA and methyl jasmonate, and the expression level of the gene was up-regulated in different hormone treatments,which indicates that the gene was involved in the positive regulation of the hormone response.

Key words: Acacia mangium, AmCesA1, gene cloning, cluster analysis, hormone response