Genomics tools for dissecting nodulation in the model legume Medicago truncatula

摘要

Approximately ten years after the elucidation of Nod factor, the lipochito-oligosaccharide made by rhizobia in response to their host plants, investigators have identified many responses to this signal in plant roots. In addition, many details of cellular function in infected roots and nodules have been discovered, principally by identifying differentially regulated genes or by analyzing function of candidate genes. However, understanding of many aspects of nodulation remains sketchy. How is the Nodfactor signal transduced in the host? Do the regulatory mechanisms that govern nodulation overlap with networks controlling other aspects of development? Are components of the nodulation machinery restricted to legumes, or perhaps to a larger clade of nodule-formers that includes actinorhizal plants? Do homologous rhizobia avoid triggering a defense response, or are such means used to optimize nodule number?