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可能会导致不平等的进化压力，这种压力被称为“性选择”。虽然性选择在动物身上得到了很好的研究，但它在植物中的存在和进化还不是很清楚。了解植物的这一过程有助于研究将作物与其野生近缘杂交的方法，从而将有用的野生性状转移到农业物种中。这项研究考察了茄属几个物种的雄配子和雌配子(花粉和胚珠)之间的化学信号变化，茄属包括重要的农作物物种：番茄、马铃薯和茄子。在大多数动植物中，配子之间的化学吸引是生殖所必需的。该项目将测量配子信号在物种内和物种之间的有效性，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。这些发现将产生关于哪些信号相互作用对受精至关重要的新信息，并更好地理解为什么以及如何进化男女信号相互作用的差异。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界代表性不足群体的个人。该项目研究了配子化学吸引中差异的机制基础，包括特定的原因分子变化，这种差异在物种之间生殖障碍(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。对野生番茄群体(Solanum)的初步研究表明，配子识别是通过一种胚珠分泌的化学吸引剂进行的，这种化学吸引剂会使正在生长的花粉管重新定向到同种的雌配子上。异种配子的特定组合表现出显著的吸引力减弱，表明在这种胚珠分泌(雌性)信号中，某些物种之间存在分歧。拟议的工作将：量化胚珠基因表达的差异和一组密切相关物种之间的配子化学吸引之间的关联；识别潜在的分子座位，描述其跨分支的分子进化模式，并将序列变化与配子吸引的功能行为差异相关联；以及评估总体上的选择，特别是性选择，是配子信号进化的驱动因素，从而在物种之间的化学吸引方面的差异。这项研究使用了半活体行为分析的组合，这些行为分析操纵相互作用的配子伙伴的身份、靶向转基因标记、功能操纵和分子进化分析，其中每一种都已经在本实验系统中开发或应用。这些发现将对配子识别分子中分子和功能差异之间的关系提供全面的经验性评估，涉及多个密切相关的物种。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.