Defining Whole-Plant Phloem Function with Molecular Studies of Anatomy

要将植物韧皮部脉管系统中糖运输的长距离流体力学行为与韧皮部和周围组织之间糖交换的短距离调节联系起来，需要对韧皮部的定量解剖学有比目前更深入的了解。韧皮部解剖学的准确测量，现在有可能与活细胞成像的转基因拟南芥植物表达mCitrine（单体黄色荧光蛋白，YFP）标记的质膜蛋白质在韧皮部筛元素。其中一些转基因（由PI开发）为共聚焦激光扫描显微镜（甚至通过活组织）提供了良好的筛元件照明。筛板和孔显示出彻底的YFP标记，为固定和切片组织的免疫组织化学荧光成像提供了希望。PI目前正在将成功的构建体出口到其他物种，包括本氏烟草（Nicotiana benthamiana）、N. tabacum和Populus，用于韧皮部解剖的跨物种比较。这些结果将有助于PI预测一组物种和植物器官中韧皮部的大规模物理化学行为，这将为其他实验提供背景，例如使用局部和化学诱导的韧皮部特异性转运蛋白沉默的全植物源和库强度的“黑匣子”操作。分析的结构也将有助于了解如何在有核的伴侣细胞表达的蛋白质被贩卖到去核筛elements.The更广泛的影响，这项研究包括美国韧皮部生物学的“重新发明”，以跨学科，从应用数学，系统生物学，分子遗传学，以及一个真正的跨学科的机会本科生培训。这项工作对于我们理解韧皮部传播的植物疾病的运动，植物资源分配以及树木在全球碳循环中的作用非常重要。

To link the long-distance fluid mechanical behavior of sugar transport in the phloem vasculature of plants with the short-distance regulation of sugar exchange between the phloem and surrounding tissue requires much deeper knowledge of the phloem's quantitative anatomy than is currently available. Accurate measurements of phloem anatomy are now possible with live-cell imaging of transgenic Arabidopsis plants that express mCitrine (monomeric yellow fluorescent protein, YFP)-labeled plasma membrane proteins in phloem sieve elements. Some of these transgenics (developed by the PI) provide excellent illumination of sieve elements for confocal laser scanning microscopy (even through live tissue). Sieve plates and pores show thorough YFP labeling, holding out the promise for immunohistochemical fluorescence imaging of fixed and sectioned tissues. The PI is currently exporting successful constructs to other species, including Nicotiana benthamiana, N. tabacum, and Populus, for cross-species comparisons of phloem anatomy. The results will help the PI to predict the gross-scale physicochemical behavior of the phloem across a set of species and plant organs, which will provide the context for other experiments, such as "black-box" manipulations of whole-plant source and sink strength using local and chemically inducible silencing of phloem-specific transporters. Analysis of the constructs will also aid in understanding how proteins expressed in nucleate companion cells are trafficked to enucleate sieve elements.The broader impacts of this study include a "re-invention" of American phloem biology to cut across disciplines, drawing from applied mathematics, systems biology, and molecular genetics, as well as a truly interdisciplinary opportunity for undergraduate training. The work could be very important for our understanding of the movement of phloem-borne plant diseases, plant resource allocation, and the role of trees in the global carbon cycle.