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）作为有性生殖的一种机制，以及它如何阻止不同物种之间的生殖事件。这项工作使用了驯化的番茄及其12种不同的野生物种亲属，它们在许多生殖和功能性状上各不相同。该项目将首先确定来自雌性配子的化学信号，吸引物种内的雄性配子。其次，它将表征该信号在物种间的变化，并将这种变化与先前观察到的物种间配子吸引力降低联系起来。除了了解正常和减弱的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野生亲缘植物之间的育种障碍。该项目将包括来自代表性不足群体的本科生的研究，以及对作物育种农业重要性的潜在见解。为了鉴定雌配子衍生的化学引诱物及其特定组织来源，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13个密切相关物种的序列和/或表达变化来评估这种信号蛋白的分子差异。这些结合的方法将明确地将分子表达模式和DNA变异与生殖行为中的功能分歧联系起来。虽然许多研究表明，物种表现出降低的性相容性，基本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研究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.