EAGER-Forgotten N-conjugate cytokinins and their active role during senescence

细胞分裂素是一种植物激素，对植物的正常生长和发育至关重要。细胞分裂素的一个关键功能是通过延迟最终的黄化和衰老（称为衰老）来保持老叶的绿色和有效生长。研究细胞分裂素如何调节衰老的延迟将有助于研究人员了解如何提高农作物的生长、性能和产量。细胞分裂素是一类约30种化学相关化合物的总称，它们调节这些生长过程。一个亚组的研究不足的细胞分裂素化合物，称为N-共轭细胞分裂素，也参与延缓叶片衰老，但他们的作用和功能是未知的。这些N-共轭细胞分裂素没有被检查了近35年，直到最近才被确定为这个发展过程的积极监管机构。本研究旨在了解这些被遗忘的细胞分裂素在叶片衰老中的作用，使用经典的生物测定和生理测量与尖端分析配对。 研究生和本科生将接受基础研究培训，高中生将获得暑期研究经验，以增加对植物科学的接触。几乎所有的细胞分裂素研究都集中在细胞分裂素碱基形式上，如反式玉米素（tZ）和异戊烯基腺嘌呤（iP），已知它们结合细胞分裂素受体并触发典型的细胞分裂素反应，如延迟衰老。然而，最近的研究结果表明，未研究的N-共轭细胞分裂素形式也可以延缓衰老，这表明这些N-共轭物在衰老过程中的作用的重新检查。生物测定将用于直接测量所有细胞分裂素形式水平的变化，并将使用GC-MS/MS确定发育期间对细胞分裂素生物合成途径的影响。衰老期间的转录组和蛋白质组分析将与细胞分裂素水平的生理学和测量平行进行，以表征响应于N-缀合物细胞分裂素与基础细胞分裂素形式特异性发生的基因表达和蛋白质变化。这项高风险和高回报的奋进应该揭示这些未被充分研究的细胞分裂素的作用，并解释不同的细胞分裂素化合物如何在分子水平上延缓衰老。该奖项反映了NSF的法定使命，并被认为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来支持。

Cytokinin is a plant hormone that is essential to normal growth and development in plants. One key function of cytokinin is to keep older leaves green and growing efficiently by delaying their eventual yellowing and aging, called senescence. Study of how cytokinin regulates the delay of senescence will help researchers learn how to increase growth, performance, and yield of agricultural crops. Cytokinin is a blanket term for a class of about 30 chemically related compounds that regulate these growth processes. A sub-group of understudied cytokinin compounds, known as N-conjugate cytokinins, are also involved in delaying leaf senescence, yet their role and function are unknown. These N-conjugate cytokinins have not been examined for nearly 35 years and only recently were identified as being active regulators of this developmental process. This research aims to understand the role of these forgotten cytokinins in leaf aging using classical bioassays and physiological measurement paired with cutting edge analyses. Graduate and undergraduate students will be trained in basic research, and summer research experiences will be offered to high school students to increase exposure to the plant sciences.Nearly all cytokinin research has focused on cytokinin bases forms like trans-Zeatin (tZ) and isopentenyladenine (iP), which are known to bind cytokinin receptors and trigger canonical cytokinin responses, such as delaying senescence. Yet recently findings indicate that the unstudied N-conjugate cytokinins forms can also delay senescence suggesting a re-examination of the role of these N-conjugate during senescence. Bioassays will be used to directly measure changes in the levels of all cytokinin forms and will use GC-MS/MS to determine effects on the cytokinin biosynthesis pathway during development. Transcriptome and proteome analyses during senescence will be conducted in parallel with physiology and measurements of cytokinin levels to characterize gene expression and protein changes that specifically occur in response to N-conjugate cytokinin vs base cytokinin forms. This high risk and high reward endeavor should uncover the role of these otherwise under-studied cytokinins and explain how different cytokinin compounds delay senescence at the molecular level over development.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.