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 Phaseolus vulgaris–rhizobia symbiotic interaction (PvADFE). PvADFE was preferentially expressed in rhizobia-inoculated roots and nodules. PvADFE 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 PvADFE 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 PvADFE reduced the nodule number, nitrogen fixation activity, average nodule diameter, as well as NODULE INCEPTION (NIN) and EARLY NODULIN2 (ENOD2) transcript accumulation. Hence, changes in ADFE transcript levels affect rhizobial infection and nodulation, suggesting that ADFE is fine-tuning these processes.

Objective: To establish the optimal conditions for genetic transformation using Agrobacterium rhizogenes (A. rhizogenes) in three bean varieties. Design/methodology/approach: The experimental black bean (LEF-UA-03) and mustard (LEF-UA-01) lines, including the commercial cultivar Pinto Saltillo, were utilized to evaluate their susceptibility to transformation with A. rhizogenes K599. Subsequently, transformation efficiency was determined using both the A. rhizogenes K599 strain and the A. rhizogenes K599 (pH35GUSGFP) strain. The integration and expression of the transgene were confirmed through the visualization of green fluorescent protein (GFP) in transformed roots, as well as through the amplification of the GFP sequence from genomic DNA by PCR. Results: In the present study, the susceptibility of three bean varieties to hairy root formation was evaluated using A. rhizogenes K599 and A. rhizogenes K599 (pH35GUSGFP). The susceptibility of the varieties ranged from 69% to 76%. Limitations on study/implications: A limitation on this study is that transformation efficiency was evaluated only under a single set of experimental conditions. Therefore, genotype dependent variability and environmental factors such as bacterial concentration that may influence transformation efficiency were not extensively explored. The high susceptibility observed in all three varieties suggests that this protocol may serve as a reliable platform for functional genomics studies. Additionally, the successful generation of transgenic hairy roots indicates potential applications in the production of valuable metabolites using hairy root cultures in controlled bioreactor systems. Findings/conclusions: All bean varieties demonstrated high susceptibility to transformation with A. rhizogenes K599 > 69%. The successful expression and molecular confirmation of the GFP reporter gene validate the effectiveness of the transformation system. These results indicate that the evaluated protocol is suitable for generating transgenic hairy roots in common bean and represents a useful tool for functional gene analysis and biotechnological applications.