Cytokinins and source-sink relationships within plants

植物是通过不断增加专门模块--如根、枝、叶、茎节、花和果实--来生长的有机体。显然，不同模块化部分的增加和增长速度必须仔细协调。像动物一样，植物也使用激素来达到适当的组织水平。细胞分裂素就是这样一组激素，它是一个大约有25-30种相关化合物的家族。它们被认为通过刺激细胞更快地分裂或加工糖来促进生长。细胞分裂素是非常具有挑战性的工作，因为它们的许多形式和极低的浓度下运作。我将研究细胞分裂素如何通过扰乱细胞分裂素的存在形式和使用四种不同系统的生产平衡来指导植物模块化生长。我们对不同形式的细胞分裂素是如何相互转化的知之甚少;因此，我将分析那些经过基因修饰以沉默基因的植物，这些基因被认为是负责将高活性细胞分裂素转化为低活性细胞分裂素的。其次，我将使用基因工程植物，特别是在果实中积累异常大浓度的细胞分裂素，以确定这些器官在为植物其余部分提供细胞分裂素方面的作用。第三，为了确定不同形式的细胞分裂素在生长的种子中的活性水平，我将研究它们对它们通常不产生的细胞分裂素形式的基因组反应。最后，我将研究真菌感染对细胞分裂素产生的潜在影响及其在导致肿瘤中的作用，这些肿瘤本质上是巨大且异常强大的生长模块。结果将与想要知道如何将更多的植物资源用于种子生产的农学家，对改变性状感兴趣的园艺家，如对分枝或开花的投资或想要了解感染过程的植物病理学家有关。最重要的是，它将促进我们对植物如何生长的认识。

Plants are organisms that grow by the constant addition of specialized modules - organs like roots, branches, leaves, stem nodes, flowers and fruits. Obviously the addition and growth rates of the different modular parts must be carefully orchestrated. Like animals, plants use hormones to achieve the appropriate level of organization. One such group of hormones is the cytokinins, a family of about 25-30 related compounds. They are thought to encourage growth by stimulating cells to divide or process sugars more quickly. Cytokinins are very challenging to work with because of the numerous forms and extremely low concentrations at which they operate. I will study how cytokinins direct plant modular growth by perturbing the forms of cytokinins present and the balance of their production using four different systems. We know very little about how the different forms of cytokinin are interconverted; therefore I will be analyzing plants that have been genetically modified to silence genes that are thought responsible for converting high to low activity cytokinins. Secondly, I will use plants genetically engineered to accumulate unusually large concentrations cytokinin specifically in fruits to determine the role of those organs in providing the rest of the plant with cytokinin. Thirdly, to determine the activity levels of different forms of cytokinin in growing seeds, I will investigate their genomic response to forms of cytokinins that they usually do not make themselves. Finally I will investigate the potential impact that fungal infection has on cytokinin production and its role in causing tumors, which are essentially large and unusually strong growing modules. Results will be relevant to agronomists wanting know how to direct more plant resources into seed production, horticulturalists interested in changing traits like investment into branching or flowering or plant pathologists who want to understand infection processes. Above all, it will advance our state of knowledge about how plants grow.