Testing genetic and evolutionary mechanisms of gamete signal divergence in Solanum

男性和女性在交配机会上的差异会导致不平等的进化压力，这被称为“性选择”。虽然性选择在动物中得到了很好的研究，但它在植物中的存在和进化却不为人所知。了解植物的这一过程有助于找到作物与其野生近缘种杂交的方法，从而允许将有用的野生性状转移到农业物种中。本研究考察了茄属几种植物中雄性和雌性配子（花粉和胚珠）之间化学信号的变化，茄属植物包括重要的作物物种：番茄、土豆和茄子。配子间的化学吸引对大多数动植物的繁殖是必不可少的。该项目将测量物种内部和物种之间配子信号的有效性，确定信号吸引力变化的遗传和化学原因，以及这种变化对受精成功模式的影响。这些发现将提供关于哪些信号相互作用对受精至关重要的新信息，并更好地理解雄性和雌性信号相互作用差异的进化原因和方式。此外，该项目将涉及研究生、本科生和高中生，包括妇女和来自科学领域代表性不足群体的个人。该项目研究配子化学吸引差异的机制基础，包括具体的因果分子变化、这种差异在物种间生殖障碍（配子隔离）中的作用，以及影响吸引信号变化率的生态和生殖条件。对野生番茄（茄属）的初步研究表明，配子识别是通过一种胚珠分泌的化学引诱剂发生的，这种化学引诱剂使生长中的花粉管重新定向到同种的雌性配子上。异种配子的特定组合显示出明显降低的吸引力，表明在胚珠分泌（雌性）信号中某些物种之间存在分歧。这项工作将：量化一组亲缘关系密切的物种内部和物种之间的胚珠基因表达差异和配子化学吸引之间的关系；鉴定潜在的分子位点，描述它们在进化中的分子进化模式，并将序列变化与配子吸引的功能行为差异联系起来；并且，评估一般的选择，特别是性选择，是配子信号进化的驱动因素，因此物种之间的化学吸引力出现了分歧。该研究结合了半体内行为分析，操纵相互作用配子伴侣的身份，靶向转基因标记，功能操作和分子进化分析，每一个都已经在这个实验系统中开发或应用。这些发现将为多个密切相关物种的配子识别分子的分子和功能差异之间的关系提供全面的经验评估。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Differences between males and females in mating opportunities can result in unequal evolutionary pressures that are termed "sexual selection." While sexual selection is well studied in animals, its existence and evolution in plants is not well known. Understanding this process in plants can contribute to methods for crossing crops with their wild relatives, thereby allowing the transfer of useful wild traits into agricultural species. This research examines variation in chemical signals between male and female gametes (pollen and ovules) in several species in the genus Solanum, a group that includes important crop species: tomato, potato and eggplant. Chemical attraction between gametes is essential for reproduction in most plants and animals. The project will measure the effectiveness of gamete signals within and between species, identify the genetic and chemical causes of variation in signal attractiveness, and the consequences of this variation for patterns of fertilization success. These findings will generate new information about which signaling interactions are essential for fertilization, and greater understanding of why and how differences in male-female signaling interactions evolve. In addition, the project will involve graduate students, undergraduates, and high school students, including women and individuals from groups that are underrepresented in the sciences. The project addresses the mechanistic basis of divergence in gamete chemoattraction, including the specific causal molecular changes, the role of this divergence in reproductive barriers (gamete isolation) between species, and the ecological and reproductive conditions that influence rates of change in the attraction signal. Preliminary research in the wild tomato group (Solanum) shows that gamete recognition occurs via an ovule-secreted chemoattractant that causes growing pollen tubes to reorient towards conspecific female gametes. Specific combinations of heterospecific gametes show significantly reduced attraction, indicating divergence between some species in this ovule-secreted (female) signal. The proposed work will: quantify the association between divergence in ovule gene expression and gamete chemoattraction within and between a group of closely related species; identify the underlying molecular loci, characterize their patterns of molecular evolution across the clade, and associate sequence changes with functional behavioral divergence in gamete attraction; and, evaluate evidence that selection in general, and sexual selection specifically, is a driver of gamete signal evolution and therefore divergence in chemoattraction between species. The research uses a combination of semi in vivo behavioral assays that manipulate the identity of interacting gametic partners, targeted transgenic markers, functional manipulation, and molecular evolutionary analysis, each of which has already been developed or applied in this experimental system. The findings will provide a comprehensive empirical assessment of the relationship between molecular and functional divergence in gamete recognition molecules, across multiple closely related species.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.