Emshwiller E, Doyle J J
L. H. Bailey Hortorium, Cornell University, Ithaca, New York 14853, USA.
Mol Phylogenet Evol. 1999 Aug;12(3):310-9. doi: 10.1006/mpev.1999.0613.
Chloroplast-expressed glutamine synthetase (ncpGS), a nuclear-encoded gene containing several introns, is introduced as a tool for phylogenetic studies at lower taxonomic levels. This gene is a member of a multigene family, but it diverged long ago from the cytosolic-expressed members of the family and appears to be single copy in the majority of taxa examined to date. The conservation of both coding sequence and position of introns has allowed the design of primers for use in a broad range of dicot taxa to amplify and sequence a region of ncpGS that contains four introns. The utility of this region in phylogenetic studies of congeneric species is illustrated by an example using eight Oxalis species. The four introns in these taxa are typical in size (76 to 136 bp), base composition (high T content), and structure (e.g., sequence of splice sites and putative branch points) for plant internal introns. Levels of variation among these ncpGS sequences compare favorably with those of the internal transcribed spacer of nuclear ribosomal DNA (ITS) from the same taxa, and results of phylogenetic analysis of ncpGS data are generally congruent with previous results using ITS.
叶绿体表达的谷氨酰胺合成酶（ncpGS）是一个含有多个内含子的核编码基因，被作为一种在较低分类水平上进行系统发育研究的工具引入。该基因是一个多基因家族的成员，但它很久以前就与该家族中胞质表达的成员分化，并且在迄今为止所研究的大多数分类群中似乎是单拷贝的。编码序列和内含子位置的保守性使得能够设计引物，用于在广泛的双子叶植物分类群中扩增和测序ncpGS的一个包含四个内含子的区域。通过使用八个酢浆草属物种的例子说明了该区域在同属物种系统发育研究中的实用性。这些分类群中的四个内含子在大小（76至136 bp）、碱基组成（高T含量）和结构（例如，剪接位点和假定分支点的序列）方面对于植物内部内含子来说是典型的。这些ncpGS序列之间的变异水平与来自相同分类群的核糖体DNA（ITS）的内部转录间隔区的变异水平相比具有优势，并且ncpGS数据的系统发育分析结果通常与使用ITS的先前结果一致。
