Cedroni M L, Cronn R C, Adams K L, Wilkins T A, Wendel J F
Departament of Botany, Iowa State University, Ames, IA 50011, USA.
Plant Mol Biol. 2003 Feb;51(3):313-25. doi: 10.1023/a:1022051100610.
R2R3-MYB transcription factors have been implicated in a diversity of plant-specific processes. Among the functions attributed to myb factors is the determination of cell shape, including regulation of trichome length and density. Because myb transcription factors are likely to play a role in cotton fiber development, the molecular evolutionary properties of six MYB genes previously shown to be expressed in cotton fiber initiation were examined. In accordance with their presumed central role, each of the genes display conservative substitution patterns and limited sequence divergence in diploid members of the genus Gossypium, and this pattern is conserved in allotetraploid cottons. In contrast to highly reiterated rDNA repeats, GhMYB homologues (duplicated gene pairs) exhibit no evidence of concerted evolution, but instead appear to evolve independently in the allopolyploid nucleus. Expression patterns for the MYB genes were examined in several organs to determine if there have been changes in expression patterns between the diploids (G. raimondii and G. arboreum) and the tetraploid (G. hirsutum) or between the duplicated copies in the tetraploid. Spatial and temporal expression patterns appear to have been evolutionarily conserved, both during divergence of the diploid parents of allopolyploid cotton and following polyploid formation. However, the duplicated copies of MYB1 in the tetraploid are not expressed at equal levels or equivalently in all organs, suggesting possible functional differentiation.
R2R3-MYB转录因子参与了多种植物特有的过程。在归因于MYB因子的功能中，包括细胞形状的确定，如对毛状体长度和密度的调控。由于MYB转录因子可能在棉花纤维发育中发挥作用，因此对先前显示在棉花纤维起始阶段表达的六个MYB基因的分子进化特性进行了研究。根据它们假定的核心作用，每个基因在棉属二倍体成员中显示出保守的替代模式和有限的序列差异，并且这种模式在异源四倍体棉花中得以保留。与高度重复的rDNA重复序列不同，GhMYB同源物（重复基因对）没有协同进化的证据，而是似乎在异源多倍体细胞核中独立进化。在几个器官中检测了MYB基因的表达模式，以确定二倍体（雷蒙德氏棉和亚洲棉）与四倍体（陆地棉）之间或四倍体中重复拷贝之间的表达模式是否发生了变化。在异源多倍体棉花的二倍体亲本分化期间以及多倍体形成之后，空间和时间表达模式在进化上似乎都是保守的。然而，四倍体中MYB1的重复拷贝在所有器官中的表达水平并不相等或等效，表示可能存在功能分化。
