Investigating Gibberellin Phytohormone Metabolism

科学价值赤霉素是一大类复杂的二萜类天然产物，其中几种在植物中具有强大的生物活性，可作为激素。有趣的是，这些植物激素不仅是由植物产生的，它们可以调节植物的生长和发育，也可以由某些与植物相关的真菌和细菌微生物产生。虽然高等植物和真菌中赤霉素植物激素的生物合成已经得到了很大程度的阐明，它们似乎独立地进化/组装了相应的代谢途径，但细菌中这种生物合成的基础仍然是谜。即使在高等植物中，赤霉素代谢的起源仍然不清楚。此外，最近的发现表明高等植物中存在新的赤霉素代谢（特别是分解代谢），这在植物生物学中具有未被探索的意义。在先前nsf支持的研究的基础上，该项目将进一步研究高等植物中的赤霉素代谢，并确定细菌中类似的生物合成途径。细菌途径似乎代表了第三个趋同进化解决方案的例子，解决了如此复杂的天然产物生物合成所带来的难题。这些研究也将为植物中赤霉素代谢的进化起源提供见解。因此，计划广泛的研究将提供一个系统发育多样化的群体生物的赤霉素植物激素代谢的全面概述。赤霉素在农业中发挥着重要作用，因为正是这种植物激素代谢的改变导致了水稻和小麦的高产半矮秆品种，这是“绿色革命”的关键组成部分。促进植物生长的细菌对赤霉素激素的生物合成通常应用于豆科作物，具有额外的农业意义。此外，高等植物对赤霉素生产的绝对需求提供了一个生物合成基因的基因库，这些基因的重复导致了一个巨大的超家族（约7000个已知的）相关的二萜天然产物，表现出各种生物活性和生理作用（例如，作为防御性抗生素）。因此，该项目虽然专门针对赤霉素代谢，但将为更广泛的天然产物群体提供见解。更广泛的影响——正在进行的更广泛的外联工作也将继续和扩大。除了将本科生、研究生和博士后学生纳入研究之外，还将继续与高中生和来自代表性不足群体的学生合作。此外，该项目还包括向初中和高中科学教师进行演讲，以提供具体的例子，说明基础研究如何成为改善人类状况的技术进步的基础和信息。一个重要的例子是上面提到的赤霉素与“绿色革命”的关系。

Scientific MeritThe gibberellins are a large group of complex diterpenoid natural products, among which several have potent biological activity in plants, where they serve as hormones. Intriguingly, these phytohormones are made not only by the plants in which they serve to regulate growth and development, but by certain plant-associated fungal and bacterial microbes as well. While gibberellin phytohormone biosynthesis has been largely elucidated for higher plants and fungi, which seem to have independently evolved/assembled the corresponding metabolic pathway, the basis for such biosynthesis in bacteria remains enigmatic. Even in higher plants, the origins of gibberellin metabolism remains obscure. Further, there have been recent discoveries demonstrating the existence of novel gibberellin metabolism (particularly catabolism) in higher plants, which have unexplored implications in plant biology. Building on previous NSF-supported studies, this project will both further investigate gibberellin metabolism in higher plants and also define the analogous biosynthetic pathway in bacteria. The bacterial pathway appears to represent yet a third example of a convergent evolutionary solution to the puzzle presented by such complex natural products biosynthesis. These studies will also provide insight into the evolutionary origins of gibberellin metabolism in plants. Thus, the planned wide-ranging studies will provide a comprehensive overview of gibberellin phytohormone metabolism in a phylogenetically diverse group organisms. Gibberellins have played an important role in agriculture, as it was alterations in such phytohormone metabolism that led to high yielding semi-dwarf varieties of rice and wheat, which were a critical component of the "Green Revolution". The biosynthesis of gibberellin phytohormones by plant growth promoting bacteria that are commonly applied to legume crop plants offers additional agricultural significance. Further, the absolute requirement for gibberellin production in higher plants has provided a genetic reservoir of biosynthetic genes, duplication of which has led to a vast super-family (~7,000 known) of related diterpenoid natural products, exhibiting various biological activities and physiological roles (e.g., as defensive antibiotics). Hence, this project, while specifically directed at gibberellin metabolism, will offer insights into a much broader group of natural products.Broader ImpactOn-going broader outreach efforts also will be continued and expanded. Beyond the inclusion of undergraduate, graduate and postdoctoral students in research, work will be continued with high school students and those from under-represented groups. In addition, the project includes presentations to junior and senior high school science teachers to provide concrete examples of how basic research underlies and informs technological advancements that improve the human condition. An important example is the relationship of gibberellin to the "Green Revolution" as noted above.