Mao Jinyan, Jia Chang, Ling Jie, Chen Yingnan
State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China.
Jiangsu Huanghai Farm Co. Ltd, Yancheng, 224000, China.
BMC Plant Biol. 2025 Feb 20;25(1):234. doi: 10.1186/s12870-025-06228-z.
Tubulin proteins, the main components of microtubules in all eukaryotes, are involved in numerous aspects of plant morphogenesis and adaptation to the environment. In woody plants, microtubules are closely associated with the orientation of cellulose microfibril deposition in the secondary xylem cells and thereby exert an influence on the strength and flexibility of wood. Three major types of tubulin proteins-α-, β- and γ-tubulin-are ubiquitously present in all flowering plants, with α- and β- tubulin serving as basic subunits of microtubules and γ-tubulin directing microtubule nucleation. Compared with herbaceous plants, information on tubulin gene family has been limited in forest trees. This study aimed to characterize the tubulin gene family in the model forest tree Populus deltoides.
Based on the whole genome sequence of P. deltoides, 25 PdTubulin genes were identified, including 6 PdTUAs, 17 PdTUBs, and 2 PdTUBGs were identified, with an uneven distribution across 14 chromosomes. Unlike Arabidopsis, which has only three pairs of tubulin paralogs, nearly all PdTubulin were paralogous duplicates, primarily generated by p-whole genome duplication (WGD), γ-WGD, or segmental duplication, indicating multiple rounds of gene family expansion. After the duplication events, the number of TUA genes in Populus was more strictly constrained compared to TUB genes. All paralogous and orthologous tubulin pairs have been under strong purifying selection. Expression analysis revealed that each PdTubulin gene was preferentially expressed in one of three organs: root, leaf, or stem. 5 PdTUB paralogs exhibited similar expression patterns, suggesting potential redundancy. Additionally, expression analysis in male and female floral buds across developmental stages indicated that different members might be involved in sex-specific processes.
微管蛋白是所有真核生物中微管的主要成分，参与植物形态发生和环境适应的多个方面。在木本植物中，微管与次生木质部细胞中纤维素微纤丝沉积的方向密切相关，从而影响木材的强度和柔韧性。三种主要类型的微管蛋白——α-、β-和γ-微管蛋白——普遍存在于所有开花植物中，α-和β-微管蛋白作为微管的基本亚基，γ-微管蛋白指导微管成核。与草本植物相比，林木中微管蛋白基因家族的信息有限。本研究旨在对模式林木三角叶杨中的微管蛋白基因家族进行表征。
基于三角叶杨的全基因组序列，鉴定出25个PdTubulin基因，包括6个PdTUAs、17个PdTUBs和2个PdTUBGs，它们在14条染色体上分布不均。与拟南芥不同，拟南芥只有三对微管蛋白旁系同源物，几乎所有的PdTubulin都是旁系同源重复基因，主要由p-全基因组复制（WGD）、γ-WGD或片段重复产生，表明基因家族经历了多轮扩展。在复制事件之后，与TUB基因相比，杨树中TUA基因的数量受到更严格的限制。所有旁系同源和直系同源的微管蛋白对都受到强烈的纯化选择。表达分析表明，每个PdTubulin基因在根、叶或茎这三个器官之一中优先表达。5个PdTUB旁系同源物表现出相似的表达模式，表明可能存在潜在的冗余。此外，对不同发育阶段的雄花芽和雌花芽的表达分析表明，不同成员可能参与性别特异性过程。
