Department of Plant Cell Biology, Radboud University Nijmegen, The Netherlands.
Mol Biol Evol. 2010 Feb;27(2):481-95. doi: 10.1093/molbev/msp279. Epub 2009 Nov 16.
The MADS-box transcription factor family has expanded considerably in plants via gene and genome duplications and can be subdivided into type I and MIKC-type genes. The two gene classes show a different evolutionary history. Whereas the MIKC-type genes originated during ancient genome duplications, as well as during more recent events, the type I loci appear to experience high turnover with many recent duplications. This different mode of origin also suggests a different fate for the type I duplicates, which are thought to have a higher chance to become silenced or lost from the genome. To get more insight into the evolution of the type I MADS-box genes, we isolated nine type I genes from Petunia, which belong to the Mgamma subclass, and investigated the divergence of their coding and regulatory regions. The isolated genes could be subdivided into two categories: two genes were highly similar to Arabidopsis Mgamma-type genes, whereas the other seven genes showed less similarity to Arabidopsis genes and originated more recently. Two of the recently duplicated genes were found to contain deleterious mutations in their coding regions, and expression analysis revealed that a third paralog was silenced by mutations in its regulatory region. However, in addition to the three genes that were subjected to nonfunctionalization, we also found evidence for neofunctionalization of one of the Petunia Mgamma-type genes. Our study shows a rapid divergence of recently duplicated Mgamma-type MADS-box genes and suggests that redundancy among type I paralogs may be less common than expected.
MADS 框转录因子家族在植物中通过基因和基因组倍增得到了极大的扩展，可以分为 I 型和 MIKC 型基因。这两类基因具有不同的进化历史。MIKC 型基因起源于古老的基因组倍增以及更近的事件，而 I 型基因座似乎经历了较高的周转率，存在许多近期的倍增。这种不同的起源模式也表明 I 型基因的命运不同，它们被认为更有可能被沉默或从基因组中丢失。为了更深入地了解 I 型 MADS 框基因的进化，我们从矮牵牛中分离出 9 个属于 Mgamma 亚类的 I 型基因，并研究了它们编码区和调控区的分化。分离出的基因可以分为两类：两个基因与拟南芥的 Mgamma 型基因高度相似，而其他七个基因与拟南芥基因的相似性较低，起源也较近。最近复制的两个基因在其编码区发现了有害突变，表达分析显示第三个旁系同源物的调控区突变使其沉默。然而，除了三个经历了非功能化的基因外，我们还发现了一个矮牵牛 Mgamma 型基因发生新功能化的证据。我们的研究表明，最近复制的 Mgamma 型 MADS 框基因迅速分化，并表明 I 型基因座的冗余可能比预期的要少。
