Abstract:

Objective: Tubulin is an important component of plant cytoskeleton and plays an important role in plant cell division and growth,cell morphology maintenance,intracellular material transport and cell wall biosynthesis. In order to comprehensively understand the molecular characteristics of tubulin in Moso bamboo(Phyllostachys edulis),the genome-wide identification and analysis of tubulin were carried out,and the gene function of PeTUA3 was preliminarily studied,intending to provide evidences for revealing the role of tubulin involved in the growth and development of Moso bamboo. Method: A genome-wide analysis of tubulin genes in Moso bamboo was conducted using bioinformatics method. The tissue expression patterns of tubulin genes and their expression changes with increasing shoot height were analyzed by transcriptome data and real-time fluorescence quantitative PCR(qPCR) respectively. The function of PeTUA3 was preliminarily studied by ectopic expression in Arabidopsis thaliana followed by phenotypic observation. Result: A total of 18 tubulin gene sequences were obtained from the Moso bamboo genome,which encoded proteins with complete conserved domains of tubulin. The length of these proteins ranged from 430 aa to 634 aa with the molecular weight of 48.31-69.89 kDa. In the phylogenetic tree constructed with tubulins of Oryza sativa and A. thaliana, they were clustered into two subfamilies(TUA and TUB),and those members of Moso bamboo were closer to those of rice,which were named as PeTUA1-PeTUA6 and PeTUB1-PeTUB12, respectively. Subcellular localization prediction showed that all the PeTUAs were localized in the cytoplasm,while all the PeTUBs were localized in the nucleus. Gene-specific expression analysis based on transcriptome data showed that there were some differences in the expression levels of different tubulin genes in seven different tissues of Moso bamboo. For example,the expression levels of PeTUA3, PeTUA6, PeTUB2 and PeTUB3 were higher in each tissue,while those of PeTUA2 and PeTUB12 were lower in all the tissues. The qPCR demonstrated that with the increasing height of bamboo shoots,all the expression of the members in TUA subfamily was upregulated,while 8 genes in TUB subfamily showed upregulation trend,and 4 genes with fluctuations,indicating they may play different roles in different developmental stages of bamboo shoots. The expression of sense PeTUA3 in A. thaliana promoted the growth of transgenic plants,especially the elongation of the main roots,while that of antisense PeTUA3 inhibited the growth of transgenic plants,and the growth of the main roots was inhibited significantly. Conclusion: Six TUA genes and 12 TUB genes were identified in Moso bamboo. The molecular characteristics of each tubulin gene were different,and the expression of each gene in different bamboo tissues and shoots at different developmental stages showed different patterns,indicating that they may play different functions in different tissues and different growth stages of the same tissue. Overexpression of PeTUA3 could affect the growth of transgenic A. thaliana plants,suggesting that PeTUA3 may play an important role in the rapid growth of bamboo.

Key words: Phyllostachys edulis, tubulin, molecular characteristics, ectopic expression