Department of Genetics, Heinrich Heine University, 40225 Düsseldorf, Germany.
Proc Natl Acad Sci U S A. 2010 Jul 27;107(30):13378-83. doi: 10.1073/pnas.1005617107. Epub 2010 Jul 12.
The most remarkable outcome of a gene duplication event is the evolution of a novel function. Little information exists on how the rise of a novel function affects the evolution of its paralogous sister gene copy, however. We studied the evolution of the feminizer (fem) gene from which the gene complementary sex determiner (csd) recently derived by tandem duplication within the honey bee (Apis) lineage. Previous studies showed that fem retained its sex determination function, whereas the rise of csd established a new primary signal of sex determination. We observed a specific reduction of nonsynonymous to synonymous substitution ratios in Apis to non-Apis fem. We found a contrasting pattern at two other genetically linked genes, suggesting that hitchhiking effects to csd, the locus under balancing selection, is not the cause of this evolutionary pattern. We also excluded higher synonymous substitution rates by relative rate testing. These results imply that stronger purifying selection is operating at the fem gene in the presence of csd. We propose that csd's new function interferes with the function of Fem protein, resulting in molecular constraints and limited evolvability of fem in the Apis lineage. Elevated silent nucleotide polymorphism in fem relative to the genome-wide average suggests that genetic linkage to the csd gene maintained more nucleotide variation in today's population. Our findings provide evidence that csd functionally and genetically interferes with fem, suggesting that a newly evolved gene and its functions can limit the evolutionary capability of other genes in the genome.
基因复制事件最显著的结果是产生新的功能。然而，关于新功能的出现如何影响其同源姐妹基因副本的进化，我们知之甚少。我们研究了雌性基因（fem）的进化，该基因最近通过串联复制在蜜蜂（Apis）谱系中衍生出互补性别决定基因（csd）。先前的研究表明，fem 保留了其性别决定功能，而 csd 的出现则建立了一个新的主要性别决定信号。我们观察到 Apis 到非 Apis fem 的非同义替换与同义替换比率的特定降低。我们在另外两个遗传上相关的基因中发现了一种相反的模式，表明 csd （处于平衡选择下的基因座）的 hitchhiking 效应不是这种进化模式的原因。我们还通过相对速率检验排除了更高的同义替换率。这些结果表明，在 csd 的存在下，更强的纯化选择作用于 fem 基因。我们提出，csd 的新功能干扰了 Fem 蛋白的功能，导致 fem 在 Apis 谱系中的分子约束和有限的可进化性。与全基因组平均水平相比，fem 中升高的沉默核苷酸多态性表明，与 csd 基因的遗传连锁在当今种群中维持了更多的核苷酸变异。我们的研究结果提供了证据表明，csd 在功能和遗传上干扰了 fem，表明新进化的基因及其功能可以限制基因组中其他基因的进化能力。
