Pollen-pistil Interactions in the Genus Nicotiana

花粉-雌蕊相互作用是控制植物繁殖的重要途径。控制烟草属花粉种内和种间识别的因素为探索这些相互作用提供了一个很好的系统。自交不亲和性烟叶中S-RNase介导的种内花粉识别已被广泛了解。此外，还很好地描述了阿拉木图与其自亲缘亲缘的种间杂交关系。这两种类型的花粉识别显然都需要花粉和雌蕊之间的相互作用。该研究项目使用生化和分子生物学工具来了解这些相互作用的分子细节。在之前的资助期内，克隆的S-RNase基因在转基因植物中表达，以研究其在控制传粉中的作用。主要结果包括：1)S-RNase控制着种内传粉的特异性；2)识别信息在S-RNase分子中广泛编码；3)至少有三种遗传上不同的机制有助于控制褐花与其自交亲缘种之间的种间传粉；4)S-RNase与种间花粉识别和排斥有关。这些结果很重要，因为它们暗示S-RNase有助于定义相容授粉的遗传亲缘关系窗口。它有拒绝自交花粉的作用，从而防止近亲繁殖。它也有拒绝种间花粉的作用，因此可以防止非常广泛的杂交。本研究的主要目标是：1)鉴定和表征与花粉识别有关的非srnase因子；2)研究RNase依赖性种间花粉排斥的特异性。已经通过差异cDNA克隆确定了一个假定的因素。这一新的序列将利用免疫学和转基因植物方法进行鉴定。cDNA克隆方法将进一步扩展到鉴定与花粉识别相关的非s - rnase因子。通过比较表达细菌RNase的转基因植物与表达S-RNase或识别缺陷S-RNase的植物的授粉行为，将解决种间花粉识别的特异性。通过了解控制烟草属植物种内和种间花粉识别的自然机制，这些研究可能有助于人为操纵重要经济植物的繁殖行为。

McClure 9604645 Pollen-pistil interactions provide an important avenue for controlling plant reproduction. The factors controlling intraspecific and interspecific pollen recognition in the genus Nicotiana provide an excellent system for exploring these interactions. A great deal is known about S-RNase mediated intraspecific pollen recognition in self-incompatible Nicotiana alata. Furthermore, the interspecific crossing relationships between N. alata and its self-compatible relatives have been well described. Both types of pollen recognition clearly entail interactions between the pollen and the pistil. This research project uses biochemical and molecular biological tools to understand the molecular details of these interactions. In the previous funding period, cloned S-RNase genes from N. alata were expressed in transgenic plants to examine their role in controlling pollination. The key results were: 1) that S-RNases control the specificity of intraspecific pollination, 2) that recognition information is diffusely encoded in the S-RNase molecule, 3) that at least three genetically distinct mechanisms contribute to controlling interspecific pollination between N. alata and its self-compatible relatives, and 4) that S-RNase was implicated in interspecific pollen recognition and rejection. These results are important because they imply that S-RNase helps to define a window of genetic relatedness for compatible pollination. It has a role in rejecting self-pollen, and thus prevents inbreeding. It also has a role in rejecting interspecific pollen, and so acts to prevent very wide crosses. The major goals in this new proposal are: 1) to identify and characterize non-SRNase factors that contribute to pollen recognition, and 2) to examine the specificity of RNase dependent interspecific pollen rejection. One putative factor has already been identified by differential cDNA cloning. This new sequence will be characterized using immunological and transgenic plant methods. The cDNA cloning appr oach will be extended to identify further non-S-RNase factors related to pollen recognition. The specificity of interspecific pollen recognition will be addressed by comparing the pollination behavior of transgenic plants expressing a bacterial RNase with plants expressing S-RNase or recognition defective S-RNase. By understanding the natural mechanisms that control intraspecific and interspecific pollen recognition in the genus Nicotiana, these studies may contribute to efforts to artificially manipulate the breeding behavior of economically important plants.