SYMBIOTIC PATHWAY IN PEANUT PLANTS IS ALTERED BY CO-INOCULATION OF BENEFICIAL AND PATHOGENIC MICROORGANISMS

FIGUEREDO, MARÍA SOLEDAD; FORMEY, DAMIEN; IBAÑEZ, FERNANDO; HERNÁNDEZ, GEORGINA; FABRA, ADRIANA

Lima

Congreso; III CONFERENCIA IBEROAMERICANA DE INTERACCIONES BENEFICIOSAS PLANTA ? MICROORGANISMO ? MEDIO AMBIENTE (IBEMPA); 2017

Peanut develops a symbiotic association with bradyrhizobia to overcome nitrogen limitation. Bradyrhizobial infection of peanut roots occurs through a poorly characterized intercellular mechanism, and nodules formed are aeschynomenoid type. With the aim to evaluate the participation of the symbiotic receptor gene Ahsymrk and miRNAs in peanut nodulation, we determined their relative expression levels through qRT-PCR in roots and nodules. Results indicated that, at 9 days post-inoculation (dpi) of Bradyrhizobium sp. SEMIA6144, the Ahsymrk expression level increased in inoculated roots. At 40 dpi, the miR399 and miR159 expression levels were higher in nodules than in roots. These results suggest that Ahsymrk, miR399 and miR159 would be implicated in peanut nodulation. In order to assess if inoculation of other beneficial or pathogenic microorganisms affects the SEMIA symbiotic behaviour we evaluated, at 40 dpi, the nodule number (NN), their size and dry weight (NDW) in plants inoculated with SEMIA and the PGPR Bacillus sp. CHEP5 or challenged with the pathogen S. rolfsii. No changes were found in the NN between plants co-inoculated and inoculated only with SEMIA. Moreover, the NDW and their size were higher in those plants, suggesting that CHEP5 improves SEMIA symbiotic behavior. In plants challenged with S. rolfsii, NN, NDW and their size decreased. In order to evaluate if Ahsymrk, miR399 and miR159 genes involved in peanut symbiosis are implicated in these phenotypic changes, we determined their expression level in roots and nodules. At 9 dpi, the transcription level of Ahsymrk in roots inoculated with SEMIA and S. rolfsii decreased compared to roots inoculated only with SEMIA, in agreement with the altered symbiotic phenotype of these plants. No changes were observed between plants co-inoculated and inoculated only with SEMIA, which is also consistent with the unaltered NN formed. Despite of changes in the symbiotic behavior, at 40 dpi, the expression levels of miR399 and miR159 in nodules from plants co-inoculated with SEMIA and CHEP5 or S. rolfsii reached same values of those from plants inoculated only with SEMIA. Results obtained suggest that Ahsymrk, miR399 and miR159 are involved in peanut-bradyrhizobia interaction, but only changes in the transcription level of Ahsymrk could be associated with the symbiotic phenotype of plants co-inoculated with another PGPR or a pathogen. Supported by UNRC, CONICET, ANPCyT.