Wei Xiao-Xin, Wang Xiao-Quan
Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Mol Phylogenet Evol. 2004 May;31(2):542-53. doi: 10.1016/j.ympev.2003.08.015.
The evolutionary dynamics of the 4CL gene encoding 4-coumarate:coenzyme A ligase was investigated in the genus Larix (Pinaceae) by comparing copy number, GC content and codon usage, sequence divergence, and phylogenetic analysis. All 4CL clones of Larix formed a strongly supported monophyletic group, in which two robust clades (4clA and 4clB) derived from an ancient gene duplication event in the common ancestor of Larix were identified. Further gene duplication in the 4clA clade gave rise to two subclades 4clA(1) and 4clA(2). Frequent duplication/deletion appears to be a common evolutionary phenomenon in the 4CL gene family and paralogous genes differ greatly in their evolution rate. The existence of L. speciosa in subclades 4clA(1) and 4clA(2) suggests that this species may represent a primitive form of Larix or the closest relative of the common ancestor of the Eurasian Sect. Multiserialis. In addition, cpDNA and nrDNA ITS analyses support the hypothesis of an early separation of Larix into a North American and a Eurasian clade, which is congruent with the results of previous allozyme and very recent AFLP analyses. The unexpected close relationship between North American larches and the short-bracted species L. gmelinii in East Asia, based on the 4CL gene tree, may stem from lineage sorting.
通过比较拷贝数、GC含量和密码子使用情况、序列分歧以及系统发育分析，研究了松科落叶松属中编码4-香豆酸:辅酶A连接酶的4CL基因的进化动态。落叶松的所有4CL克隆形成了一个得到有力支持的单系类群，其中鉴定出两个强大的分支（4clA和4clB），它们源自落叶松共同祖先中的一次古老基因复制事件。4clA分支中的进一步基因复制产生了两个亚分支4clA(1)和4clA(2)。频繁的复制/缺失似乎是4CL基因家族中常见的进化现象，旁系同源基因在进化速率上差异很大。4clA(1)和4clA(2)亚分支中存在日本落叶松，这表明该物种可能代表落叶松的原始形式或欧亚多脉叶亚组共同祖先的最亲近亲属。此外，叶绿体DNA和nrDNA ITS分析支持落叶松早期分为北美和欧亚分支的假说，这与之前的等位酶分析和最近的AFLP分析结果一致。基于4CL基因树，北美落叶松与东亚短苞鳞落叶松之间意外的密切关系可能源于谱系分选。
