Cytokinins and source-sink relationships within plants

植物是通过不断增加专门的模块而生长的有机体--根、枝、叶、茎节、花和果实等器官。显然，不同模块部件的添加和增长速度必须仔细协调。和动物一样，植物也使用荷尔蒙来达到适当的组织水平。其中一组激素是细胞分裂素，这是一个由大约25-30种相关化合物组成的家族。它们被认为通过刺激细胞分裂或更快地处理糖来促进生长。使用细胞分裂素是非常具有挑战性的，因为它们的作用形式繁多，浓度极低。我将使用四种不同的系统来研究细胞分裂素如何通过扰乱存在的细胞分裂素的形式和它们的生产平衡来指导植物的模块化生长。我们对不同形式的细胞分裂素如何相互转化知之甚少；因此，我将分析那些经过基因改造以沉默基因的植物，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，特别是在水果中积累异常高浓度的细胞分裂素，以确定这些器官在为植物的其余部分提供细胞分裂素方面所起的作用。第三，为了确定正在生长的种子中不同形式的细胞分裂素的活性水平，我将调查它们对通常不会自己制造的各种形式的细胞分裂素的基因组反应。最后，我将调查真菌感染对细胞分裂素产生的潜在影响，以及它在导致肿瘤中的作用，肿瘤本质上是巨大而异常强大的生长单元。结果将与希望知道如何将更多植物资源引导到种子生产中的农学家、对改变投资等性状(如投资于分枝或开花)感兴趣的园艺学家或希望了解感染过程的植物病理学家相关。最重要的是，它将促进我们对植物如何生长的了解。

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.