CONICET | Buscador de Institutos y Recursos Humanos

We studied the function of PvRHS24-13 (Pv13), a cDNA from common bean, previously identified as differentially expressed in root hairs of a Mesoamerican cultivar inoculated with a more competitive and efficient strain of Rhizobium etli (belonging to the nodCá genotype, which is mainly found in Mesoamerican soils) versus plants inoculated with a less efficient one (R. etli nodC ä mainly found in Andean soils). Based on sequence analysis, Pv13 encodes a member of the NBS-LRR receptor family. Regulation by exogenously added hormones was measured by qRT-PCR. Pv13 mRNAs were not significantly modified by auxin or cytokinine as compared with mock-treated plants. Salicylic and jasmonic acid also had no effect on Pv13 mRNA levels. When nitrogen was supplied in an assimilable form, a strong reduction of Pv13 mRNA was detected. To get insight into rhizobia molecules involved in the induction of this receptor, roots were inoculated with R. etli mutants deficient in the synthesis of Nod factor (NF), exopolysaccharide (EXO) or lipopolisaccharide. Results revealed that NF and EXO are both needed to induce Pv13. To detect genes encoding interactors of the Pv13 protein, a cDNA library was screened in a yeast two hybrid assay. Three positive clones were isolated, resulting in good candidates to participate in the signalling pathway. Finally, to characterize the function of Pv13, a knock-down strategy mediated by antisense RNA was developed. Phenotypic analysis showed that plants with reduced Pv13 mRNA levels also exhibited a reduction in nodulation performance. These and previous results support the idea that this receptor may have a role in common bean-rhizobia symbiosis, particularly in the plant preference for rhizobia that have presumably co-evolved with it in domestication centers.