NF-YA1, a nodule specific subunit of the heterotrimeric nuclear factor y, is required for nodule formation in common bean

CAROLINA RÍPODAS, MÉLISSE CASTAINGTS, FLAVIO BLANCO AND MARÍA EUGENIA ZANETTI

Mar del Plata

Congreso; XXIX Reunión Argentina de Fisiología Vegetal (RAFV 2012); 2012

Sociedad Argentina de Fisilogía Vegetal

Common bean (Phaseolus vulgaris) associates with its partner Rhizobium etli, resulting in the formation of root nitrogen-fixing nodules. Host-dependant competitiveness has been observed in this interaction, in which bean accessions from the Mesoamerican center of genetic diversification are more efficiently and preferentially nodulated by strains from the same geographical region. A C subunit of the heterotrimeric nuclear factor Y (NF-Y), which is required for nodule organogenesis and bacterial infection, have shown to play a role in the selection of rhizobial strains that will colonize nodules in common bean. More recently, we have identified several genes encoding the A subunit of NF-Y. From an expression pattern analysis we found that transcripts levels of the gene named NF-YA1 were almost undetectable in leaves and stems, detected at low levels in roots and 20-25 folds higher in young and mature nodules as compared to root tissue. A detailed inspection of the protein sequence showed that NF-YA1 posses the DNA binding and the subunit interaction domains, which are conserved among all eukaryotic organisms. At early stages of the interaction, NF-YA1 mRNAs accumulated only in roots inoculated with the high efficient strain of R. etli, but not with the low efficient one, suggesting that NF-YA1 might also have a function in strain specificity. Introduction of an RNAi construct designed to target the 3’UTR region of NF-YA1 reduced NF-YA1 mRNA levels in 83 to 94% and impaired nodulation by high or low efficient strains, revealing that this subunit of the NF-Y complex is also required for nodule organogenesis in common bean. The interaction between NF-YC1 and NF-YA1 subunits is currently being evaluated. Understanding the role of NF-Y complex in nodule formation and bacterial infection is crucial to elucidate the molecular basis of the functional compatibility observed between common bean and strain of rhizobia that coevolved in the same center of genetic diversification.