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

因为植物物种之间的杂交通常会导致适应性降低的后代，所以为什么杂交持续存在，甚至在自然界中相当常见，这仍然是一个谜。为了解决这个基本问题，这项研究调查了控制个体之间交配兼容性的基因。这些基因在玉米及其野生祖先teosinte的种群中分布不同。虽然这些都是同一物种的一部分，但它们代表着不同的亚种，这些亚种的一些种群很容易杂交，而另一些种群则不容易。这个系统作为一个有价值的遗传模型来研究杂交问题，特别是被忽视的植物物种之间的雄性和雌性之间的冲突。拒绝来自错误物种的花粉的雌性可以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会产生更高的适合度(促进杂交)，即使是与近缘物种或亚种的低质量后代。通过鉴定和研究这种研究得很好且具有重要经济意义的植物的交配亲和性基因，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。研究团队将在加利福尼亚州和明尼苏达州培训本科生、研究生和博士后研究人员。他们还将为加利福尼亚州的K-12学生开发课堂材料，并为明尼苏达州的高中女生提供Biomath夏令营。这项研究探讨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。该项目还探讨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对调节玉米亚种群体间杂交亲和性的三个配子体因子之一的精细定位，以便了解所有三个配子体因子周围的DNA序列背景。然后，研究人员将进行一系列遗传杂交，以确定墨西哥高原不同同域玉米和墨西哥高原类型的teosinte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，允许研究人员评估他们的数学模型的预测。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.