Collaborative Research: Molecular, Biochemical and Signal Transduction Analysis of a Phytotoxic Root-Root Communication Process Mediated by (-)-Catechin in the Rhizosphere

合作研究：根际 (-)-儿茶素介导的植物毒性根-根通讯过程的分子、生化和信号转导分析

• 批准号: 0750968
• 负责人: Simon Gilroy
• 金额: $ 2.44万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0750968&HistoricalAwards=false
• 关键词: Collaborative; Research; Molecular; Biochemical; Signal

The soil surrounding a plant root, known as the rhizosphere, is a unique physical, biochemical and ecological environment. The rhizosphere is to a large extent controlled by the root system through chemicals secreted into the surrounding soil. These root secretions (exudates) may play symbiotic or defensive roles as a plant communicates with its environment, ultimately developing a positive or negative response to the other elements in its rhizosphere. An example of negative communication is provided by the Asian native Centaurea maculosa L. (spotted knapweed). Centaurea maculosa Lam. (spotted knapweed) is one of the most invasive and destructive introduced weeds in North America, particularly in the fields and pastures of the northwest U.S. Although it has long been proposed that spotted knapweed achieves its dominance through secretion of a plant-toxic chemical (allelochemical), no such chemical had been identified until last year, when it was determined that an exudate of spotted knapweed roots is indeed toxic to other plants. The active "ingredient" of this chemical is composed of racemic catechin, a 50:50 mixture of (+)-catechin and (-)-catechin. Although (+)-catechin is widespread throughout the plant kingdom, both (-)-catechin and the racemic form are extremely rare. Further, the anti-plant part of the exudate was entirely due to (-)-catechin, while (+)-catechin was inactive. Conversely, (+)-catechin was active against certain bacteria, while (-)-catechin was not. (-)-Catechin was found to be toxic against Arabidopsis and a variety of crop plant species and was also toxic to C. diffusa (diffuse knapweed), a close relative of spotted knapweed. (-)-Catechin did not affect seedlings or seed germination of C. maculosa itself. In Arabidopsis thaliana, spotted knapweed's toxic chemical triggers a rapid cascade of stress responses which kill cells in the root meristem and elongation zone and ultimately lead to the death of the entire root system. The proposed research will shed light on the molecular and biochemical interactions that occur in conjunction with this negative communication process in the subterranean part of this plant. Specifically, the proposal will examine the negative control exerted by (-)-catechin in the rhizosphere of C. maculosa using the following aims: 1) to understand the toxic chemical processes initiated by (-)-catechin in Arabidopsis roots, 2) to understand the mechanism by which C. maculosa detoxifies (-)-catechin, and 3) to clone the gene(s) involved in (-)-catechin production. The interaction of (-)-catechin with plants such as Arabidopsis is an event that occurs under natural soil conditions, and thus has biological relevance. In addition, this research will provide the broader benefits of training two postdoctoral scholars, one graduate student and undergraduates in a multidisciplinary research atmosphere. Furthermore, the research outlined has practical implications to both U.S. agriculture and to preserving plant diversity of the Western U.S.

植物根部周围的土壤，称为根际，是一个独特的物理、生化和生态环境。根际在很大程度上是由根系通过分泌到周围土壤的化学物质来控制的。当植物与其环境沟通时，这些根分泌物(分泌物)可能起到共生或防御作用，最终对其根际中的其他元素产生积极或消极的反应。亚洲土生土长的斑点矢车菊(Centaurea maculosa L.)就是一个负面交流的例子。斑点矢车菊Centaurea maculosa Lam.在北美，特别是在美国西北部的田野和牧场，斑点金针草是入侵和破坏最严重的杂草之一。尽管长期以来一直有人提出斑点金针草的优势是通过分泌一种植物毒性化学物质(化感物质)来实现的，但直到去年才发现这种化学物质，当时确定斑点金针草根的渗出物确实对其他植物有毒。这种化学物质的活性成分由外消旋儿茶素组成，外消旋儿茶素是(+)-儿茶素和(-)-儿茶素的50：50混合物。虽然(+)-儿茶素广泛存在于整个植物界，但(-)-儿茶素和外消旋形式都极其罕见。此外，渗出物的抗植物部分完全是由于(-)-儿茶素，而(+)-儿茶素是无效的。相反，(+)-儿茶素对某些细菌有活性，而(-)-儿茶素则没有。(-)-儿茶素被发现对拟南芥和多种作物物种有毒性，对与斑点牛膝有亲缘关系的漫天牛也有毒性。(-)-儿茶素不影响黄连幼苗或种子萌发。在拟南芥中，斑点龙须草的有毒化学物质会触发快速的应激反应，杀死根分生组织和伸长区的细胞，最终导致整个根系的死亡。这项拟议的研究将阐明这种植物地下部分与这种负通讯过程相关的分子和生化相互作用。具体地说，该提案将研究(-)-儿茶素对拟南芥根际环境的负调控作用，目的如下：1)了解(-)-儿茶素在拟南芥根部引发的有毒化学过程；2)了解(-)-儿茶素解毒的机制；3)克隆参与(-)-儿茶素生产的基因(S)。(-)-儿茶素与拟南芥等植物的相互作用是在自然土壤条件下发生的事件，因此具有生物学意义。此外，这项研究将提供在多学科研究氛围中培养两名博士后学者、一名研究生和本科生的更广泛的好处。此外，概述的研究对美国农业和保护美国西部植物多样性都有实际意义。