Importance of bacteria and plant antioxidant system in peanut-Bradyrhizobium sp interaction

VANINA MUÑOZ; FERNANDO IBAÑEZ; ADRIANA FABRA

Congreso; XI Congreso Argentino de Microbiología General (SAMIGE); 2015

Peanut is a leguminous plant of great agroeconomic importance, capable of establishing a nitrogen-fixing symbiotic associationwith bacteria of the genus Bradyrhizobium. We recently demonstrated for the first time that the early events of the symbioticinteraction peanut-Bradyrhizobium sp. trigger an increase in reactive oxygen species (ROS) production (represented exclusivelyby a higher H2Ocontent), which is a prerequisite for the efficient development of root nodules. We also demonstrated that NodFactor (NF) modulates this response by enhancing the plant antioxidant machinery, specifically the activity of enzymes catalase2 (CAT) and total peroxidase (PX), contributing to the creation of adequate conditions for symbiosis development. The role ofROS is now widely accepted as well as the importance of plant and bacterial antioxidant system in signaling processes duringthe establishment of the symbiosis between rhizobia and legumes infected intarcellularly. However, in less characterizedprocesses of rhizobial infection, such as intercellular invasion that occurs in peanut-Bradyrhizobium sp. interaction, the role ofantioxidant system of both partners has not been elucidated yet. Thus, the aims of this study were a) to evaluate whether theincrease in PX activity is due to the "de novo" induction of its synthesis b) to determine the requirement of the antioxidantsystem of Bradyrhizobium sp. SEMIA 6144 in the symbiotic interaction with peanut. In order to accomplish the first aim, prx1geneexpression, which encodes a peroxidase, was analyzed using qReal-Time PCR in peanut plants inoculated withBradyrhizobium sp. SEMIA 6144 or Bradyrhizobium sp. V (strain impaired in NF production). The results indicate that NF frombradirizobios peanut symbionts modulate oxidative burst occurring in the early stages of this interaction by increasing PX