Medicago truncatula is a legume widely used as a model organism for plant biology, particularly the association between rhizobia and root nodules. In this symbiosis, bacterial nitrogen fixation supplies biologically usable nitrogen within specialized plant structures. The plant and its microbial partners contribute different parts of the process.[ref]
The 2011 draft genome study combined a large-insert assembly with additional short-read sequence data. Comparing duplicated genomic regions and genes with enhanced activity in root nodules helped investigate how gene duplication contributed to the evolution of this symbiosis.[ref]
The Medicago genome provides insight into the evolution of rhizobial symbioses by Nevin D. Young and others. Abstract and Figures 1–3, genome comparison and nodule-enhanced gene pairs
A useful comparison asks whether both copies of a duplicated gene retain nodule-associated activity or whether their expression patterns differ. Sequence similarity identifies candidate relatives; measuring activity supplies another kind of evidence about their roles.The same plant also supports questions outside nodule formation. In a 2005 study, fluorescence microscopy of green fluorescent protein-labelled Methylorubrum extorquens derivatives located bacterial cells on leaves and in some internal spaces.[ref]
Methylotrophic metabolism is advantageous for Methylobacterium extorquens during colonization of Medicago truncatula under competitive conditions by Abdoulaye Sy and others. Figure 5, confocal images and localization
This visualizes colonization. A fluorescent bacterium on a leaf does not by itself establish nitrogen fixation, nodule formation or a benefit to the host. New to topics? Read the docs here!