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往往导致后代的适应性降低，为什么杂交持续存在，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相容性的基因。这些基因在玉米及其野生祖先大刍草种群中的分布不同。虽然这些都是同一物种的一部分，玉米，他们代表不同的亚种和这些亚种的一些人口很容易杂交，而其他人没有。这一系统为研究杂交问题，特别是被忽视的植物物种的雌雄之间的冲突提供了一个有价值的遗传模型。虽然拒绝错误物种花粉的雌性避免产生低质量的后代（避免杂交），但具有可以受精的花粉的雄性，即使是与密切相关的物种或亚种产生低质量的后代，也会有更高的适应性（促进杂交）。通过识别和研究这种研究充分且具有经济重要性的植物中的交配相容性基因，该项目可能会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。该研究团队将在加州和明尼苏达州培训本科生、研究生和博士后研究人员。他们还将为加州的K-12学生开发课堂材料，并为明尼苏达州的高中女生提供生物数学夏令营。这项研究解决了花粉和风格之间的相互作用如何塑造植物拒绝错误物种花粉的能力。 该项目还讨论了花粉如何克服这一障碍。这项工作从这个过程的群体遗传模型开始，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，以及哪些参数允许花粉克服这一障碍。 工作的第二个组成部分涉及的三个配子体因子之一，调节玉米亚种的种群之间的交叉相容性，使周围的所有三个配子体因子的DNA序列上下文是已知的精细映射。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草种群配子体因子基因座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。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.