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

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

La Falda, Córdoba

Workshop; II Workshop Latinoamericano sobre PGPR; 2014

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 betterunderstanding of osmoregulation might help ín genetic strain modification, providing a powerfultool for improvements in rhizobial nodulation, nitrogen fixation and crops yield. The aim of thiswork 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 transposonmutagenesis or were generated by single cross-over method. For growing tests, strains were grownin SG minimal medium under normal or high salinity conditions.OD600 was continuously monitoredusing 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 stresscondition for further analysis. Among them, thecpdR mutantshowed to be unable to grow inhighosmolaritycondition. 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