PGI Gene Sequences and Phylogenetic Inferences in Clarkia

进化生物学已在加州年度 植物Clarkia（Onagraceae）40年，该属已 提供了一些模型系统来研究 物种，自然种群的遗传变异，以及更多 最近，分子进化。 分子研究是 启动以确定复制的 存在的胞质磷酸葡萄糖异构酶（PGI）siozyme Clarkia属的12种中，有12种缺失。 PGI催化 糖代谢的重要反应。 迄今为止，几个PGI基因 已经被部分测序了 它们有着非常复杂的 结构与19个外显子（和18个内含子），迄今已确定编码 约88%的PGI蛋白（483/550氨基酸），最大的 任何植物基因已知的外显子数量。 基因编码 来自不同Clarkia的叶绿体PGI同工酶也已被 它有一个连续的开放阅读框架，没有外显子。 在目前的项目中，额外的PGI基因编码这两个 来自有和没有重复的克拉克氏菌的同工酶将被 克隆和序列测定 序列中的证据将用于 确定复制是否发生在进化的早期 属，并保留在一些血统，但失去了在其他或 是否是最近才出现的。 由于重复的PGI表征了 种在四个分类组，但在其他三个缺席 部分，证据可以预期解决系统发育 各部门之间的关系，这是一个问题， 尽管Clarkia已经被深入研究，但它仍然很难治愈。 的 序列证据也将用于比较 质体和胞质PGIs之间的分歧。 分析 将有助于理解 分子分歧，并构成了迄今为止为数不多的研究之一 植物核基因编码蛋白质的进化。

Evolutionary Biology has been studied in the California annual plant Clarkia (Onagraceae) for four decades and the genus has provided a number of model systems in which to study the origin of species, genetic variation in natural populations and, more recently, molecular evolution. The molecular studies were initiated to determine the mode of origin of the duplicated cytosolic phosphoglucose isomerase (PGI) siozymes that are present in 12 Clarkia species but absent in 12 others. PGI catalyzes an essential reaction in sugar metabolism. To date, several PGI genes have been partially sequenced. They have remarkably complex structure with 19 exons (and 18 introns) so far identified encoding about 88% of the PGI protein (483/550 amino acids), the largest number of exons known for any plant gene. A gene encoding the chloroplast PGI isozyme from a different Clarkia has also been sequenced; it has a continuous open reading frame with no exons. During the current project, additional PGI genes encoding both isozymes from clarkias with and without the duplication will be cloned and sequenced. Evidence from the sequences will be used to determine whether the duplication occurred early in the evolution of genus and was retained in some lineages but lost in others or whether it arose more recently. Since duplicated PGIs characterize species in four taxonomic sections but are absent in three other sections, the evidence can be expected to resolve the phylogenetic relationships among the sections, a problem that has remained refractory even though Clarkia has been studied intensively. The sequence evidence will also be used to compare the rate and amount of divergence between the plastid and cytosolic PGIs. The analysis will contribute to understanding the mechanisms that generate molecular divergence and constitutes one of the few studies to date of the evolution of plant nuclear genes encoding proteins.