"Membranes homeoviscous adaptation in Sinorhizobium submitted to a stressful thermal cycle contributes to the maintenance of the symbiotic interaction with Medicago sativa"

PAULUCCI N; CESARI A; BIASUTTI A; DARDANELLI M; PERILLO MA

Córdoba

Congreso; LI Reunión Anual de la Sociedad Argentina de Biofisica; 2023

SAB

Membranes homeoviscous adaptation in Sinorhizobium submitted to astressful thermal cycle contributes to the maintenance of the symbioticinteraction with Medicago sativaPaulucci Na, Cesari Aa, Biasutti Ab, Dardanelli Ma, Perillo MAca - Instituto de biotecnologia ambiental y salud (INBIAS). CONICETb - Instituto para el desarrollo agroindustrial y de la salud (IDAS)c - 1 – Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra deQuímica Biológica. Córdoba, Argentina. 2 – Instituto de Investigaciones Biológicas y Tecnológicas (IIByT –CONICET UNC). Córdoba, Argentina.An environmentally friendly practice is the inoculation of alfalfa with Sinorhizobiummeliloti that can fix atmospheric nitrogen in symbiosis and promote plant growth. Toestablish an effective symbiosis, the first step involves the incorporation by the bacteria ofthe flavonoid exuded by the alfalfa roots (luteolin) that will allow the expression of thenecessary genes for the production of Nod factors. These will allow the formation of thethread of infection and the root nodule. Temperature is one of the most variableenvironmental factors and can cause changes in the cell envelope ofbacteria, which can then translate into changes in their ability to establish symbiosis withalfalfa. We estimate fast changes in the fluidity of S. meliloti membranes submitted tocyclic temperature changes (10ºC–40ºC–10ºC) by monitoring the fluorescencepolarization (P) of DPH and TMA-DPH of the whole cell (WC) as well as in its outer (OM) andinner (IM)membranes. Additionally, the long-term response to thermal changes is demonstratedthrough the dynamics of the phospholipid and fatty acid composition in each membrane.This allowed membrane homeoviscous adaptation by the return to optimal fluidity levelsas measured by the PDPH/TMA-DPH in WC, OM, IM, and multilamellar vesicles of lipidsextracted from OM and IM. Due to probe-partitioning preferences and membranes’compositional characteristics, DPH and TMA-DPH exhibit different behaviors in IM and OM.The rapid effect of cyclic temperature changes on the P was the opposite in bothmembranes with the IM being the one that exhibited the thermal behavior expected forlipid bilayers.Interestingly, only after the incubation at 40ºC, cells were unable to recover themembrane preheating P levels when cooled up to 10ºC. Solely in this condition, theformation of threads and nodular structures in alfalfa infected with S. meliloti weredelayed, indicating that the symbiotic interaction was partially altered but not halted.AcknowldegmentsThis study was financially supported by PIP CONICET (Grant No. 11220150100232CO), SeCyT-UNRC(Grant No. 161/126), PICT (Grant No. 1065/15), PICT (Grant No. 4162/18), SeCyT-UNC (Grant No.33620180100680CB) PICT (Grant No. 4420/2018), and PIP CONICET (Grant No. 11220200103025CO).