Metallothionein1A Regulates Rhizobial Infection and Nodulation in .

Metallothioneins (MTs) constitute a heterogeneous family of ubiquitous metal ion-binding proteins. In plants, MTs participate in the regulation of cell growth and proliferation, protection against heavy metal stress, oxidative stress responses, and responses to pathogen attack. Despite their wide variety of functions, the role of MTs in symbiotic associations, specifically nodule-fabacean symbiosis, is poorly understood. Here, we analyzed the role of the gene in - symbiosis using bioinformatics and reverse genetics approaches. Using in silico analysis, we identified six genes encoding MTs in , which were clustered into three of the four classes described in plants. transcript levels were significantly higher in roots inoculated with at 7 and 30 days post inoculation (dpi) than in non-inoculated roots. Functional analysis showed that downregulating by RNA interference (RNAi) reduced the number of infection events at 7 and 10 dpi and the number of nodules at 14 and 21 dpi. In addition, nodule development was negatively affected in :RNAi transgenic roots, and these nodules displayed a reduced nitrogen fixation rate at 21 dpi. These results strongly suggest that plays an important role in the infection process and nodule development in during rhizobial symbiosis.