Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, College of Life Sciences, Zhejiang University, Hangzhou, China.
BMC Evol Biol. 2013 Jul 8;13:143. doi: 10.1186/1471-2148-13-143.
GSK3 (glycogen synthase kinase 3) genes encode signal transduction proteins with roles in a variety of biological processes in eukaryotes. In contrast to the low copy numbers observed in animals, GSK3 genes have expanded into a multi-gene family in land plants (embryophytes), and have also evolved functions in diverse plant specific processes, including floral development in angiosperms. However, despite previous efforts, the phylogeny of land plant GSK3 genes is currently unclear. Here, we analyze genes from a representative sample of phylogenetically pivotal taxa, including basal angiosperms, gymnosperms, and monilophytes, to reconstruct the evolutionary history and functional diversification of the GSK3 gene family in land plants.
Maximum Likelihood phylogenetic analyses resolve a gene tree with four major gene duplication events that coincide with the emergence of novel land plant clades. The single GSK3 gene inherited from the ancestor of land plants was first duplicated along the ancestral branch to extant vascular plants, and three subsequent duplications produced three GSK3 loci in the ancestor of euphyllophytes, four in the ancestor of seed plants, and at least five in the ancestor of angiosperms. A single gene in the Amborella trichopoda genome may be the sole survivor of a sixth GSK3 locus that originated in the ancestor of extant angiosperms. Homologs of two Arabidopsis GSK3 genes with genetically confirmed roles in floral development, AtSK11 and AtSK12, exhibit floral preferential expression in several basal angiosperms, suggesting evolutionary conservation of their floral functions. Members of other gene lineages appear to have independently evolved roles in plant reproductive tissues in individual taxa.
Our phylogenetic analyses provide the most detailed reconstruction of GSK3 gene evolution in land plants to date and offer new insights into the origins, relationships, and functions of family members. Notably, the diversity of this "green" branch of the gene family has increased in concert with the increasing morphological and physiological complexity of land plant life forms. Expression data for seed plants indicate that the functions of GSK3 genes have also diversified during evolutionary time.
GSK3（糖原合成激酶 3）基因编码信号转导蛋白，在真核生物的各种生物过程中发挥作用。与动物中观察到的低拷贝数形成对比的是，GSK3 基因在陆生植物（有胚植物）中扩展为多基因家族，并且在各种植物特有的过程中也进化出了功能，包括被子植物的花发育。然而，尽管之前已经做了很多努力，陆生植物 GSK3 基因的系统发育仍然不清楚。在这里，我们分析了来自具有系统发育关键分类群的代表样本的基因，包括基生被子植物、裸子植物和颈卵器植物，以重建陆生植物 GSK3 基因家族的进化历史和功能多样化。
最大似然系统发育分析确定了一个具有四个主要基因复制事件的基因树，这些事件与新的陆生植物类群的出现相一致。从陆生植物的祖先继承的单个 GSK3 基因首先沿着现存维管植物的祖先分支复制，随后发生了三次复制，在 euphyllophytes 的祖先中产生了三个 GSK3 基因座，在种子植物的祖先中产生了四个，在被子植物的祖先中至少产生了五个。Amborella trichopoda 基因组中的单个基因可能是源自现存被子植物祖先的第六个 GSK3 基因座的唯一幸存者。在花发育中具有遗传确认作用的两个拟南芥 GSK3 基因（AtSK11 和 AtSK12）的同源物在几个基生被子植物中表现出花偏好表达，表明其花功能的进化保守性。其他基因谱系的成员似乎在个别分类群的植物生殖组织中独立进化出了作用。
我们的系统发育分析提供了迄今为止对陆生植物 GSK3 基因进化的最详细重建，并为该家族成员的起源、关系和功能提供了新的见解。值得注意的是，随着陆生植物生活形式的形态和生理复杂性的增加，这个“绿色”分支的基因家族的多样性也增加了。种子植物的表达数据表明，GSK3 基因的功能在进化过程中也多样化了。
