Nodulation and Lateral Root Formation in the Model Legume Lotus Japonicus

豆科植物固氮根瘤的形成是在两种不同生物（即植物宿主和共生细菌）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，以支持原核共生体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，但关于植物对这一过程的贡献还有很多有待了解。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着明显的联系。本研究的具体目的是验证在模式豆科植物日本莲根的侧根形成和根瘤器官发生中存在共同调控因子的假说，这一假说特别适合于遗传、生理和分子的综合分析。我们所分离的日本松（L. japonicus） har-1突变体，其根形态发生了巨大的变化，结瘤特性也发生了异常，为本研究提供了实验依据。通过对该突变体和相应基因的表征，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，以便将结瘤过程扩展到目前未结瘤的作物，例如谷物。

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.