A New Approach to the Study of Symplastic Phloem Loading

共塑韧皮部负荷研究的新方法

基本信息

  • 批准号:
    0444119
  • 负责人:
  • 金额:
    --
  • 依托单位:
  • 依托单位国家:
    美国
  • 项目类别:
    Continuing Grant
  • 财政年份:
    2005
  • 资助国家:
    美国
  • 起止时间:
    2005-02-01 至 2009-01-31
  • 项目状态:
    已结题

项目摘要

The first step in transporting nutrients from leaves to harvestable organs, such as fruits and tubers, is to load them into the long-distance transport tissue, the phloem. This is a metabolically active process that creates within the phloem a very high concentration of nutrient, primarily sugar. Water follows by osmosis, and since the cell walls are rigid, pressure rises. The pressure, more than ten times that of an automobile tire, drives long-distance flow, just as the water pressure in a house drives water along a garden hose. Thus, loading is the motivating force for movement of nutrients, and is a direct determinate of agricultural yield. Two, species-specific mechanisms of phloem loading are known. In one, apoplastic loading, sucrose exits photosynthetic leaf cells and enters the cell wall space (apoplast). It is then energetically pumped into phloem cells by transmembrane transporter proteins. In the second loading mechanism, sucrose diffuses from its point of origin into the phloem, passing from cell to cell through narrow pores (plasmodesmata) that join them. It may seem unlikely that a process based on diffusion could concentrate sugar in cells. However, the hypothesis of this project is that this second system operates by "polymer trapping." According to this hypothesis, sucrose molecules in the phloem are converted to larger sugars, raffinose and stachyose, that are unable to diffuse back through the plasmodesmata because of their size. Sugar thus becomes concentrated, and the phloem pressure rises. Many vigorously growing plants, such as pumpkins, use this system.The polymer trap model is supported by several lines of evidence, including a strict correlation between extraordinarily high numbers of plasmodesmata in the phloem of certain species, and the transport of raffinose and stachyose. However, further experimentation has been limited by the fact that none of these species has been known to be readily transformable with foreign DNA. It was recently discovered that Verbascum phoeniceum, a raffinose/stachyose plant, can be easily transformed by standard techniques. Hence, it has become possible to test the polymer trap model.First, plants will be genetically engineered to produce yeast invertase in the apoplast. Invertase degrades sucrose. In apoplastic loaders, this treatment severely interferes with loading since the transporter proteins are specific for sucrose. However, a prediction is that loading will not be compromised in V. phoeniceum since sucrose never enters the apoplast. In the second set of experiments, sucrose transporter genes will be down regulated by RNA-interference technology. Again, this treatment abolishes loading in apoplastic loaders but is predicted to have little affect in V. phoeniceum, since transporters are not involved. In the third set of experiments, synthesis of raffinose and stachyose will be down regulated in V. phoeniceum. The expectation here is that loading will be severely inhibited because the plant cannot make the sugars needed to trap carbohydrate in the phloem and there will be no way to generate pressure by osmosis.Broader Impacts: The PI places considerable emphasis on science writing for the mass media. One of the PI's graduate students, Sarah Davidson, has begun a non-traditional, program of science communication within the traditional Field of Plant Biology and in collaboration with the Communication Department. The intention is to pave a permanent, new track in graduate school that other students will follow. Other recent articles from the PI's lab include an entry on phloem transport for MacMillan's reference encyclopedia "Biology" and a review article on phloem loading for BioScience, a journal widely read by biology teachers (in preparation).
将营养物质从叶片运输到可收获的器官(如果实和块茎)的第一步是将它们装载到长距离运输组织韧皮部中。 这是一个代谢活跃的过程,在韧皮部内产生非常高浓度的营养物质,主要是糖。 水通过渗透作用流动,由于细胞壁是刚性的,压力上升。 这种压力是汽车轮胎的十倍以上,可以驱动长距离的水流,就像房子里的水压驱动水沿着沿着花园的水管流动一样。因此,负荷是养分运动的动力,是农业产量的直接决定因素。第二,韧皮部装载的种特异性机制是已知的。 在一种情况下,质外体加载,蔗糖离开光合叶细胞并进入细胞壁空间(质外体)。 然后通过跨膜转运蛋白将其有力地泵入韧皮部细胞。 在第二种装载机制中,蔗糖从其起源点扩散到韧皮部,通过连接细胞的狭窄孔(胞间连丝)从细胞传递到细胞。 基于扩散的过程似乎不太可能将糖集中在细胞中。 然而,这个项目的假设是,这第二个系统通过“聚合物捕获”来运行。“根据这一假设,韧皮部中的蔗糖分子转化为较大的糖,棉子糖和水苏糖,由于它们的大小,它们无法通过胞间连丝扩散回来。 糖因此变得浓缩,韧皮部压力上升。 许多生长旺盛的植物,如南瓜,都使用这种系统。聚合物陷阱模型得到了几条证据的支持,包括某些物种韧皮部中极高数量的胞间连丝与棉子糖和水苏糖的运输之间的严格相关性。 然而,进一步的实验受到以下事实的限制,即已知这些物种中没有一个容易用外源DNA转化。 最近发现,毛蕊花(Verbascum phoeniceum),一种棉子糖/水苏糖植物,可以通过标准技术容易地转化。 因此,它已成为可能的测试聚合物陷阱模型。首先,植物将基因工程产生酵母转化酶的质外体。 转化酶降解蔗糖。 在质外体装载器中,这种处理严重干扰装载,因为转运蛋白对蔗糖具有特异性。 然而,预测的是,由于蔗糖从未进入质外体,因此在V. phoeniceum中的装载不会受到损害。 在第二组实验中,蔗糖转运蛋白基因将通过RNA干扰技术下调。 同样,这种处理消除了质外体装载器中的装载,但预计对V. phoeniceum的影响很小,因为转运蛋白不参与其中。 在第三组实验中,棉子糖和水苏糖的合成将在V. phoeniceum中下调。 这里的期望是,由于植物不能制造将碳水化合物捕获在韧皮部中所需的糖,并且没有办法通过渗透作用产生压力,因此负载将受到严重抑制。更广泛的影响:PI相当重视为大众媒体撰写科学文章。 PI的研究生之一,莎拉·戴维森,已经开始了一个非传统的,在植物生物学的传统领域内的科学传播计划,并与通信部门合作。 这样做的目的是为研究生院铺平一条永久的新道路,让其他学生效仿。 PI实验室最近的其他文章包括MacMillan参考百科全书“生物学”中关于韧皮部运输的条目和生物科学杂志上关于韧皮部装载的评论文章,生物学教师广泛阅读的杂志(准备中)。

项目成果

期刊论文数量(0)
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Robert Turgeon其他文献

Complexity untwined: The structure and function of cucumber (Cucumis sativus L.) shoot phloem
  • DOI:
    10.1111/tpj.15229
  • 发表时间:
    2021
  • 期刊:
  • 影响因子:
  • 作者:
    Xiaolei Sui;Jing Nie;Huan Liu;Tao Lin;Xuehui Yao;Robert Turgeon
  • 通讯作者:
    Robert Turgeon
Amborella trichopoda, plasmodesmata, and the evolution of phloem loading
  • DOI:
    10.1007/s00709-010-0237-2
  • 发表时间:
    2010-11-16
  • 期刊:
  • 影响因子:
    2.500
  • 作者:
    Robert Turgeon;Richard Medville
  • 通讯作者:
    Richard Medville
Efflux of sucrose from minor veins of tobacco leaves
  • DOI:
    10.1007/bf00395471
  • 发表时间:
    1984-05-01
  • 期刊:
  • 影响因子:
    3.800
  • 作者:
    Robert Turgeon
  • 通讯作者:
    Robert Turgeon
Structure of grafted crown-gall teratoma shoots of tobacco: Regulation of transformed cells
  • DOI:
    10.1007/bf00385316
  • 发表时间:
    1981-10-01
  • 期刊:
  • 影响因子:
    3.800
  • 作者:
    Robert Turgeon
  • 通讯作者:
    Robert Turgeon
Photosynthetic acclimation in the context of structural constraints to carbon export from leaves
  • DOI:
    10.1007/s11120-006-9123-3
  • 发表时间:
    2007-01-09
  • 期刊:
  • 影响因子:
    3.700
  • 作者:
    William W. Adams;Amy M. Watson;Kristine E. Mueh;Véronique Amiard;Robert Turgeon;Volker Ebbert;Barry A. Logan;Andrew F. Combs;Barbara Demmig-Adams
  • 通讯作者:
    Barbara Demmig-Adams

Robert Turgeon的其他文献

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{{ truncateString('Robert Turgeon', 18)}}的其他基金

Heterogeneity in the phloem of minor veins
小静脉韧皮部的异质性
  • 批准号:
    1354718
  • 财政年份:
    2014
  • 资助金额:
    --
  • 项目类别:
    Standard Grant
Passive Phloem Loading
韧皮部被动加载
  • 批准号:
    1121254
  • 财政年份:
    2012
  • 资助金额:
    --
  • 项目类别:
    Continuing Grant
Conference: The Fifth International Conference on Plasmodesmatal Biology to be held in Monterey Peninsula, California on August 17-21, 2004.
会议:第五届国际胞间连丝生物学会议将于2004年8月17-21日在加利福尼亚州蒙特利半岛举行。
  • 批准号:
    0422312
  • 财政年份:
    2004
  • 资助金额:
    --
  • 项目类别:
    Standard Grant
Collaborative Research: Photosynthetic Acclimation, Photoprotection, and Phloem Loading
合作研究:光合适应、光保护和韧皮部负载
  • 批准号:
    0235709
  • 财政年份:
    2003
  • 资助金额:
    --
  • 项目类别:
    Standard Grant
Conference: Fourth International Workshop in Plasmodesmatal Biology, to be held August 19-24, 2001 in Cape Town, South Africa.
会议:第四届胞间连丝生物学国际研讨会,将于 2001 年 8 月 19-24 日在南非开普敦举行。
  • 批准号:
    0110589
  • 财政年份:
    2001
  • 资助金额:
    --
  • 项目类别:
    Standard Grant
Plasmodesmata and Phloem Loading
胞连丝和韧皮部装载
  • 批准号:
    0110638
  • 财政年份:
    2001
  • 资助金额:
    --
  • 项目类别:
    Standard Grant
Phloem Transport Without Phloem Loading
无韧皮部装载的韧皮部运输
  • 批准号:
    9603152
  • 财政年份:
    1997
  • 资助金额:
    --
  • 项目类别:
    Continuing grant
Conference: 3rd International Workshop in Plasmodesmal Biology to be held in Zichron Yakov, Israel, from March 10- 15, 1996
会议:第三届胞间连丝生物学国际研讨会将于 1996 年 3 月 10 日至 15 日在以色列 Zichron Yakov 举行
  • 批准号:
    9514724
  • 财政年份:
    1996
  • 资助金额:
    --
  • 项目类别:
    Standard Grant
The Function of Intermediary Cells in Leaves
叶子中间细胞的功能
  • 批准号:
    9419703
  • 财政年份:
    1995
  • 资助金额:
    --
  • 项目类别:
    Continuing grant
Sink-Source Transition in Leaves: A Model
叶子中的库-源转变:模型
  • 批准号:
    9104159
  • 财政年份:
    1991
  • 资助金额:
    --
  • 项目类别:
    Continuing grant

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