Yoo Mi-Jeong, Albert Victor A, Soltis Pamela S, Soltis Douglas E
Department of Botany, University of Florida, Gainesville, FL 32611, USA.
BMC Plant Biol. 2006 Feb 21;6:3. doi: 10.1186/1471-2229-6-3.
The glycogen synthase kinase 3 (GSK3)/SHAGGY-like kinases (GSKs) are non-receptor serine/threonine protein kinases that are involved in a variety of biological processes. In contrast to the two members of the GSK3 family in mammals, plants appear to have a much larger set of divergent GSK genes. Plant GSKs are encoded by a multigene family; analysis of the Arabidopsis genome revealed the existence of 10 GSK genes that fall into four major groups. Here we characterized the structure of Arabidopsis and rice GSK genes and conducted the first broad phylogenetic analysis of the plant GSK gene family, covering a taxonomically diverse array of algal and land plant sequences.
We found that the structure of GSK genes is generally conserved in Arabidopsis and rice, although we documented examples of exon expansion and intron loss. Our phylogenetic analyses of 139 sequences revealed four major clades of GSK genes that correspond to the four subgroups initially recognized in Arabidopsis. ESTs from basal angiosperms were represented in all four major clades; GSK homologs from the basal angiosperm Persea americana (avocado) appeared in all four clades. Gymnosperm sequences occurred in clades I, III, and IV, and a sequence of the red alga Porphyra was sister to all green plant sequences.
Our results indicate that (1) the plant-specific GSK gene lineage was established early in the history of green plants, (2) plant GSKs began to diversify prior to the origin of extant seed plants, (3) three of the four major clades of GSKs present in Arabidopsis and rice were established early in the evolutionary history of extant seed plants, and (4) diversification into four major clades (as initially reported in Arabidopsis) occurred either just prior to the origin of the angiosperms or very early in angiosperm history.
糖原合酶激酶3（GSK3）/类SHAGGY激酶（GSKs）是非受体丝氨酸/苏氨酸蛋白激酶，参与多种生物学过程。与哺乳动物中GSK3家族的两个成员不同，植物似乎拥有更多不同的GSK基因。植物GSKs由一个多基因家族编码；对拟南芥基因组的分析揭示了10个GSK基因的存在，这些基因分为四个主要类别。在此，我们对拟南芥和水稻GSK基因的结构进行了表征，并对植物GSK基因家族进行了首次广泛的系统发育分析，涵盖了分类学上多样的藻类和陆地植物序列。
我们发现，GSK基因的结构在拟南芥和水稻中总体上是保守的，尽管我们记录了外显子扩展和内含子丢失的例子。我们对139个序列的系统发育分析揭示了GSK基因的四个主要分支，它们与最初在拟南芥中识别的四个亚组相对应。所有四个主要分支中都有基部被子植物的EST；基部被子植物鳄梨（Persea americana）的GSK同源物出现在所有四个分支中。裸子植物序列出现在分支I、III和IV中，红藻紫菜（Porphyra）的一个序列是所有绿色植物序列的姐妹序列。
我们的结果表明：（1）植物特有的GSK基因谱系在绿色植物历史早期就已建立；（2）植物GSKs在现存种子植物起源之前就开始多样化；（3）拟南芥和水稻中存在的四个主要GSK分支中的三个在现存种子植物的进化历史早期就已建立；（4）分化为四个主要分支（如最初在拟南芥中报道的）发生在被子植物起源之前或被子植物历史的极早期。
