Plant derived peroxidases and chitinases are involved in the early steps of peanut-bradyrhizobia symbiotic interaction

FERNANDO IBAÑEZ; MARÍA SOLEDAD FIGUEREDO; JOHAN STIBEN RODRIGUEZ MELO; ADRIANA FABRA

Londrina

Congreso; XXVII Reunion Latinoamericana de Rizobiología; 2016

ALAR

Plant derived peroxidases and chitinases are involved in the early steps of peanut-bradyrhizobia symbiotic interaction Peanut, like most legumes, develops a symbiotic relationship with rhizobia to overcome nitrogen limitation. Rhizobial infection of peanut roots occurs through a primitive and poorly characterized intercellular mechanism, and nodule induction responds to an aeschynomenoid morphogenetic programme. In contrast to symbiosis development in model legumes, knowledge of the molecular determinants involved in peanut-rhizobia interaction is scarce, and little is known about the molecules implicated in the symbionts recognition. Advances in the knowledge of the molecular bases of intercellular infection will contribute to the understanding of the evolution of symbiosis, and might allow the identification of target molecules for further improving of the association through biotechnological applications. With the aim of gaining insight into the plant molecules involved in early recognition events in peanut-bradyrhizobium symbiosis, we determine the relative expression levels of Ahprx1 and Ahchi13 (genes encoding for a peanut peroxidase and a chitinase, respectively) after rhizobial inoculation. Real-Time PCR determinations were carried out with cDNA synthesized from RNA extracted at 0, 1, 8, 16 and 24 hours Post-Inoculation (PI), and the threshold cycle (Ct) was determined in triplicates. Relative transcription levels were calculated using actin as housekeeping gene by the 2- ΔΔCt method. Results indicated that both genes (Ahprx1 and Ahchi13) displayed different levels of upregulation at all the time points analyzed (1, 8, 16 and 24 hours PI). These data indicate that these molecules are involved in the early steps of the molecular pathway that leads to nodule development in this particular symbiotic interaction. Afterwards, in order to assess if expression of these genes was Nod factor dependent, we also analyze their transcription levels after inoculation with a NF defective bradyrhizobial mutant. For Ahchi13, results showed a transcriptional profile similar to that obtained for plants inoculated with wild type strain, indicating that the expression of this gene is not induced by Nod factor perception. On the other hand, Ahprx1 was only upregulated at 16 and 24 hours PI with the mutant strain, suggesting that Nod factor perception can modulate the expression levels of this gene. Further experiments will reveal if transcription of these genes is exclusively related to rhizobial perception or if they respond to any biotic interaction.Financial Support: SECyT UNRC, CONICET, ANPCyT-SECyT.Keywords: Symbiosis, Molecular dialogue, Plant determinants