Evaluation of two cgmponent systems role in saline stress response in Sinorhizobium meliloti

ALBICORO, FRANCISCO JAVIER; MARTINI, MARÍA CARLA; NILSSON JULIET; SALAS, MARÍA EUGENIA; LOPEZ, JOSÉ LUIS; LOZANO, MAURICIO JAVIER; TORRES TEJERIZO, GONZALO; BECKER, ANKE; LAGARES, ANTONIO; DEL PAPA, MARÍA FLORENCIA

La Falda, Cordaba

Workshop; II Latin American PGPR Workshop; 2014

Evaluation of two component systems role in saline stress response in Sinorhizobium meliloti Albicoro F.J.l., Martini M.C. t, Nilsson J. 1, Salas M.E. t, López J.L. t, Lozano M.J. t, Torres Tejerizo G.A.t, Becker A. 2, Lagares A. 1, Del Papa M.F. 1 tIBBM - lnstituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata {ONICET, La Plata, Argentina. tSyNMlfRO, LOEWE-zentrum für Synthetische Mikrobiolog¡e - Vergleichende, Philipps-Universitát Marburg, Alemania. Contact: floppv(obiol.unlp.edu.ar Sinorhizabium meliloti is capable of establishing a symbiotic relationship with legume roots where nitrogen fixation takes place leading to an improved plant development. This organism needs to overcome dífferent stress conditionslike high-osmolarityenvironments. The response of the cells is a fundamental biological question. As most bacterial species, the so-called two-component systems (TCS) are part of the complex and diverse mechanisms involved in such responses. A better understanding of osmoregulation might help ín genetic strain modification, providing a powerful tool for improvements in rhizobial nodulation, nitrogen fixation and crops yield. The aim of this work was to study the role of TCSs involved in high salinity response in Sinorhizobium meliloti. S. meliloti 20tL response regulator (RR) mutants were obtained either by a TnS transposon mutagenesis or were generated by single cross-over method. For growing tests, strains were grown in SG minimal medium under normal or high salinity conditions.OD600 was continuously monitored using an ELISA microplate reader. ln order to study the role of TCSs in salinity tolerance in S. meliloti, a collection of response regulators mutants was obtained. Growing rates were determined for each RR mutant as well as for the parental strain either in GS medium (normal conditions) or GS medium supplemented with 0,5M NaCl (high salt condition). Continuous measurement of OD600over time allowed us to determine whích mutants exhibited a differential growth understress conditions. Mutants showing a differential growth rate were chosen as candidates to studywhether the correspondíng RR ís dírectly or indirectly implicated in salinity stress response. This analysis enabled us to select Tmutants that showed a reduced growth rate ín the stress condition for further analysis. Among them, thecpdR mutantshowed to be unable to grow in highosmolaritycondition. Although this gene has been described as crucial for cell differentiationinto bacteroidsand co-ordination of cell cycle events, nothing was reported yet about its contribution to high salinity response/tolerance.