Understanding the molecular function of individual causal loci at the heterostyly supergene in Primula

异花柱是一种促进近亲繁殖的迷人适应，也是植物学的经典范例。在最常见的异质花柱类型中，植物形成的花要么有长花柱和短雄蕊，要么有短花柱和长雄蕊。这种相互的器官定位减少了花粉的浪费，促进了异花授粉，从而提高了雄性的适应性。此外，在许多异花柱物种中，自交和由于近交抑制而产生的不适合后代受到自交不亲和系统的限制，从而促进了雌性的适合度。在报春花（Primula）中，这两种花的形式是由s位点作为一个复杂的超基因遗传决定的，即染色体区域包含几个控制不同性状（如花柱或雄蕊长度）的单个基因，并且由于抑制重组而通过非常紧密的连锁结合在一起。在过去的几年里，我们已经确定并开始对报春花s座超基因上的个体因果位点进行功能表征，特别是关注由CYP734A50调节的花柱长度和雌性自交不亲和型的雌性性状，以及由GLO2控制的花药位置。最近，我们还获得证据表明，迄今为止知之甚少的花粉大小和雄性自交不亲和特性是由KFB-T和pumt基因之间的相互作用控制的。这些研究为更详细地了解编码蛋白如何在修饰形态之间的异质性状中发挥作用以及它们如何在进化过程中获得这些性状奠定了基础。为了解决这些问题，我们将(1)确定GLO2新功能化的结构和分子基础；(2)详细描述了KFB-T和pumt在调节花粉大小和雄性自交不亲和型中的作用；(3)利用衍生的同源报春花基因型，阐明雌性自交不亲和反应的分子基础。总之，这些研究将为植物遗传学和进化的教科书问题提供前所未有的见解，并为植物和动物的超基因进化和功能提供模型。

Heterostyly is a fascinating adaptation to promote outbreeding and a classical paradigm of botany. In the most common type of heterostyly, plants either form flowers with long styles and short stamens, or short styles and long stamens. This reciprocal organ positioning reduces pollen wastage and promotes cross-pollination, thus increasing male fitness. In addition, in many heterostylous species selfing and the generation of unfit progeny due to inbreeding depression is limited by a self-incompatibility system, thus promoting female fitness. In primroses (Primula) the two floral forms are genetically determined by the S-locus as a complex supergene, i.e. a chromosomal region containing several individual genes that control the different traits, such as style or stamen length, and are held together by very tight linkage due to suppressed recombination. Over the last years, we have identified and begun to functionally characterize the individual causal loci at the S-locus supergene in Primula, with a particular focus on the female traits of style length and female self-incompatibility type regulated by CYP734A50, and on the control of anther position by GLO2. More recently, we have also obtained evidence that the hitherto poorly understood characters of pollen size and male self-incompatiblity are controlled by an interplay between the KFB-T and PUM-T genes. These studies lay the groundwork for a more detailed mechanistic understanding of how the encoded proteins fulfil their roles in modifying the suite of heterostyly traits between the morph and how they have gained these in the course of evolution. To address these issues, we will (1) determine the structural and molecular basis for the neofunctionalization of GLO2; (2) characterize in detail the role of KFB-T and PUM-T in regulating pollen size and male self-incompatibility type; and (3) use derived homostylous Primula genotypes to elucidate the molecular basis of the female self-incompatibility reaction. Together, these studies will provide unprecedented insight into a textbook problem in plant genetics and evolution and a model for supergene evolution and function in plants and animals.