Role of phloem-mobile sucrose and auxin in the development of the root system

韧皮部移动蔗糖和生长素在根系发育中的作用

• 批准号: 0951302
• 负责人: Jocelyn Malamy
• 金额: $ 39万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-03-01 至 2013-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0951302&HistoricalAwards=false
• 关键词: Role; phloem; mobile; sucrose; auxin

Plant growth relies on the activity of stem cells clustered at shoot tips, leaf margins, and root tips, and also stem cell clusters that are quiescent and await activation. The activity of these so-called meristems determines whether plants are tall with few branches, short and bushy, etc. Similarly, the architecture of the root system is determined by the activity of meristems at the tips of primary and lateral roots, and the initial activation of these meristems in root primordia. It is essential that the activity of the plant's many meristems is coordinated to produce a plant whose morphology is optimized for its habitat. Indeed, root and shoot system growth is known to be coordinated, but how this coordination occurs is poorly understood. Previous studies clearly demonstrated that artificially increasing sucrose within a physiological range in the leaves dramatically stimulates lateral root formation, suggesting that the sucrose normally produced by leaves through photosynthesis is regulating root system development. This implicates a long distance mechanism that communicates the sucrose status of the aerial tissues to the root system. Sucrose moves from shoot to root system via the phloem, where it is unloaded at root meristems based on the steep concentration gradient. Interestingly, the plant hormone auxin is also produced in the leaves and moved to the root system via the phloem, This project will investigate how photosynthate from aerial tissues drives phloem allocation to root meristems, delivering auxin and thereby regulating their activity. This project will use transgenic plants that alter the levels of sucrose and auxin translocated in the phloem, together with fluorescent dyes that allow direct visualization of phloem movement and delivery, to test this model. If successful, the results from this project will 1) demonstrate that phloem acts to integrate plant organ development at different locations; and 2) determine the molecular signal that is carried in the phloem. This would be one of very few examples in which coordinated development in the whole-plant is understood mechanistically at the physiological and molecular levels. The broader impacts of this project include training of students at all levels and scientific outreach to the community.

植物的生长依赖于聚集在茎尖、叶缘和根尖的干细胞的活性，也依赖于静止等待激活的干细胞群。这些所谓的分生组织的活动决定了植物是高而少枝，还是矮而密等。同样，根系的结构是由主根和侧根尖端分生组织的活性以及根原基中这些分生组织的初始激活决定的。重要的是，植物的许多分生组织的活动是协调的，以产生一个植物的形态优化其栖息地。事实上，根和芽系统的生长是相互协调的，但这种协调是如何发生的却知之甚少。以往的研究清楚地表明，在一定的生理范围内，人为地增加叶片中蔗糖的含量，会显著地刺激侧根的形成，这表明通常由叶片通过光合作用产生的蔗糖正在调节根系的发育。这暗示了一种远距离机制，将地上组织的蔗糖状态传递给根系。蔗糖通过韧皮部从茎部转移到根系统，并根据陡峭的浓度梯度在根分生组织中卸载。有趣的是，植物激素生长素也在叶片中产生，并通过韧皮部转移到根系。本项目将研究来自空中组织的光合作用如何驱动韧皮部分配到根分生组织，传递生长素，从而调节其活性。该项目将使用转基因植物来改变韧皮部中蔗糖和生长素的转运水平，同时使用荧光染料来直接观察韧皮部的运动和输送，以测试这个模型。如果成功，该项目的结果将1)证明韧皮部在不同位置整合植物器官的发育；2)确定韧皮部携带的分子信号。这将是在生理和分子水平上理解整个植物协调发展的极少数例子之一。该项目的更广泛影响包括培训各级学生和向社区推广科学。