The role(s) played by plant hormones in the regulation of symbiotic structures

植物激素在共生结构调节中的作用

• 批准号: 183727-2007
• 负责人: Guinel, Frederique
• 金额: $ 2.33万
• 依托单位: Wilfrid Laurier University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2011
• 资助国家: 加拿大
• 起止时间: 2011-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=476405
• 关键词: role; played; plant; hormones; regulation

I study the mutualistic interaction which exists between certain beneficial bacteria, the rhizobia, and legume plants. As the result of this interaction, the rhizobia penetrate the plant root hairs and trigger the formation of a novel structure known as the nodule. If the symbiosis is successful, the rhizobia, now hosted within the nodule, fix atmospheric nitrogen. When fixed in excess, the nitrogen becomes available to the plant. The early infection stages are thought to require two opposing chemical gradients across the cortex of the root; the successful integration of these gradients by the partners results in the initiation of the nodule. The first gradient is rhizobial in nature; complex molecules known as Nod factors are thought to be directed towards the root centre. This gradient triggers the first cell divisions of the inner cortex and the first morphological changes of the root hairs. The other gradient oriented towards the root surface is thought to involve plant hormones, specifically auxin and cytokinin (CK). In this application, I propose that, in response to the rhizobial infection, CKs coming from the vascular tissues located in the centre of the root move across several cell layers and accumulate into the inner cortical cells where they promote cell divisions. I postulate that the CKs pooled in these cells give positional information to the rhizobia, i.e., they act as a beacon, "attracting" the rhizobia towards the cells cluster. To demonstrate that CKs are important signals for nodule initiation, I will (1.) create plant chimeras with altered CK levels; (2.) inoculate the chimeras and track the rhizobial infection at the cellular level; and (3.) follow the expression of molecular markers specific for certain steps of the infection. The methods used here will likely boost the use of pea as a model plant system as this plant is now amenable to molecular techniques. In the far future, results obtained in my research program could lead to the development of methods that could override mechanisms which prevent the proper establishment of the rhizobial symbiosis. Agronomically, this development would be extremely worthwhile since successful infections of plants by rhizobia are a key step to reducing the use of chemical fertilizers on crop plants.

我研究某些有益细菌、根瘤菌和豆科植物之间存在的互利相互作用。 这种相互作用的结果是，根瘤菌穿透植物根毛，并引发一种称为根瘤的新结构的形成。 如果共生成功，现在寄居在根瘤内的根瘤菌就能固定大气中的氮。当氮被过量固定时，植物就可以利用氮。早期感染阶段被认为需要两个相反的化学梯度穿过根的皮层;这些梯度的成功整合的合作伙伴的结果在结节的开始。第一个梯度是根瘤菌的性质;被称为结瘤因子的复杂分子被认为是指向根中心的。这种梯度触发了内皮层的第一次细胞分裂和根毛的第一次形态变化。另一个梯度朝向根表面，被认为涉及植物激素，特别是生长素和细胞分裂素（CK）。在这个应用程序中，我建议，在响应根瘤菌感染，CKs来自位于根的中心的维管组织移动跨越几个细胞层，并积累到内皮层细胞，在那里他们促进细胞分裂。我假设这些细胞中汇集的CK为根瘤菌提供了位置信息，即，它们充当信标，将根瘤菌“吸引”到细胞簇。 为了证明CK是结节形成的重要信号，我将（1.）产生具有改变的CK水平的植物嵌合体;（2.）在细胞水平上检测嵌合体并追踪根瘤菌感染;以及（3.）随后是对感染的某些步骤具有特异性的分子标记的表达。这里使用的方法可能会促进豌豆作为模式植物系统的使用，因为这种植物现在适合于分子技术。在遥远的将来，我的研究项目所获得的结果可能会导致开发出能够克服阻止根瘤菌共生正确建立的机制的方法。 从农艺学上讲，这一发展将是非常值得的，因为根瘤菌成功地感染植物是减少作物上化学肥料使用的关键一步。