DISSERTATION RESEARCH: Identifying the pollen tube chemoattractant regulating gamete recognition in the wild tomato clade (Solanum sect. Lycopersicon)

本研究旨在了解配子识别（雄性和雌性配子相互识别和吸引的化学线索）作为有性生殖的机制，以及它如何防止不同物种之间的生殖事件。本研究使用了驯化番茄及其12种不同的野生近缘种，它们在许多生殖和功能性状上存在差异。该项目将首先确定物种内雌性配子产生的吸引雄性配子的化学信号。其次，它将描述这种信号在物种间的变化，并将这种变化与之前观察到的物种间配子吸引力减少联系起来。除了了解正常和减弱生殖功能的分子机制外，这些数据还有助于克服驯化番茄与其遗传多样性的野生近缘种之间的育种障碍。该项目将包括来自代表性不足群体的本科生的研究，以及对作物育种的农业重要性的潜在见解。为了鉴定雌性配子来源的化学引诱剂及其特定组织来源，本项目将使用高深度核苷酸测序技术（RNA-seq）进行组织特异性表达分析。它将通过序列和/或表达在13个密切相关的物种中的变化来评估该信号蛋白的分子分化。这些结合的方法将明确地将分子表达和DNA变异模式与生殖行为的功能差异联系起来。尽管许多研究表明，物种表现出较低的性相容性，但其潜在的分子机制通常是未知的。总之，这项研究将提供一个前所未有的机会来检查生殖分子进化变化的模式和后果，包括新物种的发展。

This study aims to understand gamete recognition (chemical cues used by male and female gametes to recognize and attract each other) as a mechanism of sexual reproduction, and how it acts to prevent reproductive events between different species. This work uses the domesticated tomato and its twelve diverse wild species relatives, which vary in many reproductive and functional traits. The project will first identify the chemical signal derived from the female gamete that attracts the male gamete within species. Second, it will characterize variation in this signal across species and connect this variation to previously observed reduced gamete attraction between species. In addition to understanding molecular mechanisms of normal and attenuated reproductive function, these data could aid in overcoming breeding barriers between domesticated tomato and its genetically diverse wild relatives. This project will include research by undergraduates from underrepresented groups and potential insights of agricultural importance for crop breeding. To identify the female gamete-derived chemoattractant and its specific tissue of origin, this project will use high depth nucleotide sequencing technologies (RNA-seq) for tissue specific expression analysis. It will assess molecular divergence of this signaling protein via variation in sequence and/or expression across 13 closely related species. These combined approaches will explicitly link patterns of molecular expression and DNA variation to functional divergence in reproductive behaviors. Although many studies have demonstrated that species show reduced sexual compatibility, the underlying molecular mechanisms are generally unknown. Together, this research will provide an unprecedented opportunity to examine the patterns and consequences of evolutionary changes in a reproductive molecule, including for the development of new species.