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(雄配子和雌配子用来识别和吸引彼此的化学线索)作为有性繁殖的一种机制，以及它如何防止不同物种之间的生殖事件。这项工作使用了驯化的番茄和它的12个不同的野生物种近亲，它们在许多生殖和功能特征上存在差异。该项目将首先识别从物种内吸引雄配子的雌配子中获得的化学信号。其次，它将表征这种信号在不同物种之间的差异，并将这种差异与之前观察到的物种之间配子吸引力降低联系起来。除了了解正常和衰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亲之间的育种障碍。该项目将包括来自代表性不足群体的本科生的研究，以及对农业对作物育种重要性的潜在见解。为了识别雌性配子衍生的化学诱导剂及其特定的组织来源，该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。它将通过在13个密切相关物种中的序列和/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和DNA变异的模式与生殖行为中的功能差异联系起来。虽然许多研究表明，物种表现出降低的性亲和力，但其潜在的分子机制通常尚不清楚。总而言之，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，包括对新物种的发展。

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.