Collaborative research: The Evolutionary Genetics of Pollen-Pistil Incompatibility and Reproductive Isolation in Zea mays

由于植物物种之间的杂交通常会导致后代的适应性降低，所以为什么杂交会持续存在，甚至在自然界中相当普遍，这仍然是一个谜。为了解决这个基本问题，本研究调查了控制个体之间交配兼容性的基因。这些基因在玉米种群及其野生祖先大刍草种群中分布不同。Zea说，虽然这些是同一物种的一部分，但它们代表了不同的亚种，这些亚种的一些种群容易杂交，而另一些种群则不能。该系统为研究植物的杂交问题，特别是被忽视的雄性和雌性之间的冲突提供了有价值的遗传模型。拒绝来自错误物种的花粉的雌性会避免产生低质量的后代（避免杂交），而拥有可以受精的花粉的雄性，即使与密切相关的物种或亚种产生低质量的后代，也会有更高的适合度（促进杂交）。通过鉴定和研究这种被充分研究并具有重要经济意义的植物的潜在交配兼容性基因，该项目可能确定允许或阻止物种避免杂交的力量。这项研究结合了计算、数学和遗传方法来解决这些问题。研究团队将在加州和明尼苏达州培养本科生、研究生和博士后研究人员。他们还将为加州的K-12学生开发课堂教材，并为明尼苏达州的高中女生提供Biomath夏令营。这项研究解决了花粉和花柱之间的相互作用如何塑造植物拒绝来自错误物种的花粉的能力。该项目还研究了花粉如何克服这一障碍。这项工作从这一过程的种群遗传模型开始，并询问哪些参数允许雌性有效地拒绝来自另一个亚种的花粉，哪些参数允许花粉克服这一障碍。这项工作的第二个组成部分涉及到三个配子体因子中的一个的精细绘图，这些因子调节玉米亚种种群之间的杂交相容性，以便了解所有三个配子体因子的DNA序列背景。然后，研究人员将进行一系列遗传杂交，以确定墨西哥高地不同同域玉米和墨西哥型大刍动物种群配子体因子位点上替代等位基因的频率。最后，这些等位基因将被测序，使研究人员能够评估他们的数学模型的预测。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。

Because hybridization between plant species often results in offspring with reduced fitness, it remains a mystery why hybridization persists and is even fairly common in nature. To address this fundamental question, this research investigates genes that control the mating compatibility between individuals. These genes are distributed differently among populations of corn and its wild ancestor, teosinte. Although these are parts of the same species, Zea mays, they represent distinct subspecies and some populations of these subspecies interbreed easily and others do not. This system serves as a valuable genetic model to investigate the problem of hybridization and especially an overlooked conflict between males and females of the plant species. While females that reject pollen from the wrong species avoid producing low quality offspring (avoiding hybridization), males with pollen that can fertilize, and produce even low quality offspring with closely related species or subspecies will have higher fitness (promoting hybridization). By identifying and studying the genes underlying mating compatibility in this well-studied and economically important plant, this project may determine the forces that allow or prevent species from avoiding hybridization. This research combines computational, mathematical, and genetic approaches to address these questions. The research team will train undergraduates, graduate students, and postdoctoral researchers in California and Minnesota. They will also develop classroom materials for K-12 students in California and offer Biomath summer camps for high school girls in Minnesota.This research addresses how interactions between the pollen and style shape the ability of a plant to reject pollen from the wrong species. The project also addresses how pollen may overcome this barrier. The work begins with a population genetic model of this process, and asks which parameters allow for females to effectively reject pollen from another subspecies, and which parameters allow pollen to overcome this barrier. A second component of the work involves the fine mapping of one of the three gametophyte factors that modulate cross compatibility between populations of Zea mays subspecies so that the DNA sequence context around all three gametophyte factors is known. Researchers will then conduct a series of genetic crosses to identify the frequency of alternative alleles at the gametophyte factor loci in different sympatric maize and mexicana-type teosinte populations in the Mexican highlands. Finally, these alleles will be sequenced, allowing the researchers to evaluate the predictions of their mathematical model.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.