Schein Manja, Yang Ziheng, Mitchell-Olds Thomas, Schmid Karl J
Department of Genetics and Evolution, Max-Planck-Institute of Chemical Ecology, Jena, Germany.
Mol Biol Evol. 2004 Apr;21(4):659-69. doi: 10.1093/molbev/msh059. Epub 2004 Jan 22.
It has been shown in a variety of species that genes expressed in reproductive tissues evolve rapidly, which often appears to be the result of positive Darwinian selection. We investigated the evolution of a family of seven pollen-specific oleosin-like proteins (or oleopollenins) in Arabidopsis thaliana and two closely related species. More than 30 kb of a genomic region that harbors the complete, tandemly repeated oleopollenin cluster were sequenced from Arabidopsis lyrata ssp. lyrata, and Boechera drummondii. A phylogenetic analysis of the complete gene cluster from these three species and from Brassica oleracea confirmed its rapid evolution resulting from gene duplication and gene loss events, numerous amino acid substitutions, and insertions/deletions in the coding sequence. Independent duplications were inferred in the lineages leading to Arabidopsis and to Brassica, and gene loss was inferred in the lineage leading to B. drummondii. Comparisons of the ratio of nonsynonymous (d(N)) and synonymous (d(S)) divergence revealed that the oleopollenins are among the most rapidly evolving proteins currently known from Arabidopsis and that they may evolve under positive Darwinian selection. Reverse transcriptase polymerase chain reaction analysis demonstrated the expression of oleopollenins in flowers of the outcrossing A. lyrata, the selfing B. drummondii, and the apomictic Boechera holboellii, suggesting that oleopollenins play an important role in species with different breeding systems. These results are consistent with a putative function in species recognition, but further analyses of protein function and sequence variation in species with different breeding systems are necessary to reveal the underlying causes for the rapid evolution of oleopollenins.
在多种物种中已表明，在生殖组织中表达的基因进化迅速，这往往似乎是正向达尔文选择的结果。我们研究了拟南芥及其两个近缘物种中一个由七个花粉特异性油质蛋白样蛋白（或油花粉蛋白）组成的家族的进化。从琴叶拟南芥、长柄芥中对包含完整的、串联重复的油花粉蛋白簇的超过30 kb的基因组区域进行了测序。对这三个物种以及甘蓝的完整基因簇进行系统发育分析，证实了其因基因复制和基因丢失事件、大量氨基酸替换以及编码序列中的插入/缺失而导致的快速进化。推断在导致拟南芥和甘蓝的谱系中发生了独立的复制事件，在导致长柄芥的谱系中发生了基因丢失事件。非同义（d(N)）与同义（d(S)）分歧率的比较表明，油花粉蛋白是目前已知的拟南芥中进化最快的蛋白质之一，并且它们可能在正向达尔文选择下进化。逆转录酶聚合酶链反应分析表明，油花粉蛋白在异交的琴叶拟南芥、自交的长柄芥和无融合生殖的全缘叶长柄芥的花中表达，这表明油花粉蛋白在具有不同繁殖系统的物种中发挥重要作用。这些结果与在物种识别中的假定功能一致，但需要对具有不同繁殖系统的物种中的蛋白质功能和序列变异进行进一步分析，以揭示油花粉蛋白快速进化的潜在原因。
