State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, Beijing 100093, China.
Planta. 2012 Oct;236(4):1247-60. doi: 10.1007/s00425-012-1684-0. Epub 2012 Jun 19.
The inflated calyx syndrome (ICS) is a post-floral novelty within Solanaceae. Previous work has shown that MPF2-like MADS-box genes have been recruited for the development and evolution of ICS through heterotopic expression from vegetative to floral organs. ICS seems to be a plesiomorphic trait in Physaleae, but it has been secondarily lost in some lineages during evolution. We hypothesized that molecular and functional divergences of MPF2-like proteins might play a role in the loss of ICS. In this study we analyzed the phylogeny, selection and various functions of MPF2-like proteins with respect to the evolution of ICS. Directional selection of MPF2-like orthologs toward evolution of ICS was detected. While auto-activation capacity between proteins varies in yeast, MPF2-like interaction with floral MADS-domain proteins is robustly detected, hence substantiating their integration into the floral developmental programs. Dimerization with A- (MPF3) and E-function (PFSEP1/3) proteins seems to be essential for ICS development within Solanaceae. Moreover, the occurrence of the enlarged sepals, reminiscent of ICS, and MPF2-like interactions with these specific partners were observed in transgenic Arabidopsis. The interaction spectrum relevant to ICS seems to be plesiomorphic, reinforcing the plesiomorphy of this trait. The inability of some MPF2-like to interact with either the A-function or any of the E-function partners characterized is correlated with the loss of ICS in the lineages that showed a MPF2-like expression in the calyx. Our findings suggest that, after recruitment of MPF2-like genes for floral development, diversification in their coding region due to directional selection leads to a modification of the MADS-domain protein interacting spectrum, which might serve as a constraint for the evolution of ICS within Solanaceae.
泡桐杯萼综合征（ICS）是茄科植物中的一种花期后 novelty。先前的研究表明，MPF2 样 MADS-box 基因通过从营养器官到花器官的异位表达，被招募用于 ICS 的发育和进化。ICS 似乎是 Physaleae 中的一个原始特征，但在进化过程中，它在一些谱系中已经被二次丢失。我们假设 MPF2 样蛋白的分子和功能分化可能在 ICS 的丢失中起作用。在这项研究中，我们分析了 MPF2 样蛋白的系统发育、选择和各种功能，以探讨其与 ICS 进化的关系。MPF2 样直系同源物在向 ICS 进化过程中存在定向选择。尽管在酵母中，MPF2 样蛋白的自动激活能力存在差异，但在酵母中检测到其与花 MADS 结构域蛋白的稳健相互作用，因此证实了它们整合到花发育程序中。与 A 功能（MPF3）和 E 功能（PFSEP1/3）蛋白的二聚化对于茄科植物中 ICS 的发育似乎是必需的。此外，在转基因拟南芥中观察到增大的萼片的发生，类似于 ICS，并且观察到 MPF2 样蛋白与这些特定伴侣的相互作用。与 ICS 相关的相互作用谱似乎是原始的，这加强了该特征的原始性。一些 MPF2 样蛋白不能与 A 功能或任何 E 功能伴侣相互作用的特征与在萼片中表现出 MPF2 样表达的谱系中 ICS 的丢失有关。我们的研究结果表明，在 MPF2 样基因被招募用于花发育之后，由于定向选择导致其编码区的多样化，导致 MADS 结构域蛋白相互作用谱的改变，这可能是茄科植物中 ICS 进化的一个限制因素。
