Pollen-pistil interactions and reproductive isolation in maize and teosinte

生殖隔离对物种形成至关重要。 这可以通过地理隔离或通过使植物生长在一起以防止外来植物群体的花粉受精来实现。 一些植物通过使用物种特异性的传粉者（例如单一的昆虫物种）来防止外来花粉的受精，以仅将正确的花粉传递到花的雌性部分，称为雌蕊。 然而，在风授粉物种中，许多类型的花粉都可以落在雌蕊上，生殖隔离是通过其他方式实现的，包括雌蕊对外来花粉粒的生理排斥。 人们对这种生殖隔离的理解很少，因为不同类型的植物不能杂交在一起。 第二种策略的一个例子发生在玉米的野生祖先大刍草的一些菌株和栽培玉米之间。 据推测，在玉米栽培过程中发生了对可以拒绝玉米花粉的大刍草的选择。 由于杂交种可以在受控条件下通过用大刍草为玉米植株授粉而产生，这种情况为研究风媒作物植株中的生理、生殖隔离提供了模型系统。通过用大刍草花粉杂交玉米雌性，这种性状已被赋予一些玉米品系，并且在许多情况下，该性状由单一基因座，大刍草杂交障碍1（Tcb 1）控制。 Tcb1基因位于4号染色体的一个小区域。本项目拟克隆Tcb 1基因并测定其DNA序列。 随着该基因的DNA序列的已知，由Tcb 1编码的蛋白质创建一个障碍玉米花粉的方式可以进行研究，Tcb 1样基因在风媒传粉植物家族的生殖隔离和物种形成的作用的研究将是可能的。 这个项目的更广泛的影响包括对物种形成的分子基础的更深入的理解，其影响远远超出了这个研究系统。 该项目还为高中生、本科生和博士后研究人员提供了培训机会。

Reproductive isolation is critical for speciation. This can be achieved by geographic isolation or by having plants that grow together to prevent fertilization by pollen from foreign populations of plants. Some plants prevent fertilization by foreign pollen by using a species-specific pollinator, such as a single insect species, to deliver only the correct pollen to the female parts of the flower, called the pistil. However, in wind-pollinated species in which many types of pollen can land on the pistil, reproductive isolation is achieved in other ways, including the physiological rejection of foreign pollen grains by the pistil. This type of reproductive isolation is poorly understood because of the simple fact that plants of different types cannot be crossed together. An example of this second strategy occurs between some strains of teosinte, the wild progenitor of maize, and cultivated maize. It is postulated that selection for teosintes that can reject maize pollen has occurred during maize cultivation. Because hybrids can be made in controlled conditions by pollinating maize plants with teosinte, this situation provides a model system for the study of physiological, reproductive isolation in a wind-pollinated crop plant. By crossing maize females by teosinte pollen this trait has been conferred to some maize lines, and in many cases the trait is controlled by a single locus, Teosinte crossing barrier1 (Tcb1). The Tcb1 gene has been located to a small region of chromosome 4. In this project, the Tcb1 gene is to be cloned and its DNA sequence determined. With the DNA sequence of the gene known, the manner in which the protein encoded by Tcb1 creates a barrier to maize pollen can be studied, and studies of the role of Tcb1 like genes in reproductive isolation and speciation of wind-pollinated plant families will be possible. The broader impacts of this project include a greater understanding of the molecular basis for speciation, which has implications far beyond this study system. This project also provides training opportunities for high school students, undergraduate students and a postdoctoral researchers.