Nodulation and Lateral Root Formation in the Model Legume Lotus Japonicus

IBN-9630189 de Bruin和Szczyglowski豆科植物上固氮根瘤的形成代表了在植物寄主和共生细菌两种不同生物的影响下，外部诱导器官发生的一个不寻常的例子。这种共生过程产生了适当的微环境，以支持原核生物对氮的固定和植物宿主对氮的同化。虽然在细菌共生体中参与根瘤诱导的遗传成分已经得到了相对较好的研究，但关于植物在这一过程中的贡献仍有许多需要了解。初步的遗传数据表明，根瘤形态发生与其他植物发育过程之间存在明显的联系。这一建议的具体目的是检验模式豆科植物莲花的侧根形成和根瘤器官发生都涉及共同调控元件的假设，这一假说特别适合于结合遗传、生理和分子分析。我们分离到的日本乳杆菌HAR-1突变体，表现出根部形态的急剧变化以及异常的结瘤特性，并作为这一提议的实验基础。通过鉴定这个突变体和相应的基因(S)，我们希望更多地了解导致结瘤的遗传决定因素。从长远来看，这些信息可能有助于建立所需的知识库，以便将结瘤过程推广到目前未结瘤的作物，如谷物。

IBN-9630189 de Bruin and Szczyglowski The formation of nitrogen fixing nodules on legume plants represents an unusual example of externally induced organogenesis under the influence of two different organisms, namely the plant host and symbiotic bacteria. This symbiotic process results in the creation of the appropriate microenvironment necessary to support the fixation of nitrogen by the prokaryotic symbiont and the assimilation of nitrogen by the plant host. Although the genetic components involved in nodule induction have been relatively well studies in the bacterial symbiont, a lot remains to be learned about the plant's contribution to the process. Preliminary genetic data have suggested a distinct connection between nodule morphogenesis and other plant developmental processes. The specific aim of this proposal is to test the hypothesis that common regulatory elements are involved in both lateral root formation and nodule organogenesis in the model legume Lotus japonicus, which is particularly amenable to combined genetic, physiological and molecular analyses. The L. japonicus har-1 mutant we have isolated, displays a drastically altered root morphology, as well as aberrant nodulation properties, and serves as the experimental basis of this proposal. By characterizing this mutant and the corresponding gene(s), we hope to learn more about the genetic determinants responsible for nodulation. In the very long run, this information may contribute towards the knowledge base required to extend the nodulation process to presently non-nodulated crop plants, such as the cereals.