Actin Depolymerizing Factor Modulates Rhizobial Infection and Nodule Organogenesis in Common Bean.

Actin plays a critical role in the rhizobium-legume symbiosis. Cytoskeletal rearrangements and changes in actin occur in response to Nod factors secreted by rhizobia during symbiotic interactions with legumes. These cytoskeletal rearrangements are mediated by diverse actin-binding proteins, such as actin depolymerization factors (ADFs). We examined the function of an ADF in the -rhizobia symbiotic interaction (). was preferentially expressed in rhizobia-inoculated roots and nodules. promoter activity was associated with root hairs harbouring growing infection threads, cortical cell divisions beneath root hairs, and vascular bundles in mature nodules. Silencing of using RNA interference increased the number of infection threads in the transgenic roots, resulting in increased nodule number, nitrogen fixation activity, and average nodule diameter. Conversely, overexpression of reduced the nodule number, nitrogen fixation activity, average nodule diameter, as well as () and () transcript accumulation. Hence, changes in transcript levels affect rhizobial infection and nodulation, suggesting that ADFE is fine-tuning these processes.