Regulation of the subpolar flagellum synthesis in Bradyrhizobium diazoefficiens

DARDIS, CAROLINA; FLORENCIA MENGUCCI; ALTHABEGOITI, M. JULIA; ANÍBAL R. LODEIRO; QUELAS, J. IGNACIO; ELÍAS J. MONGIARDINI

Buenos Aires

Congreso; 52th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2016

Sociedad Argentina de Investigación en Bioquimica y Biologia Molecular (SAIB)

Bradyrhizobium diazoefficiensis the soybean nitrogen-fixing symbiont commonly used in inoculant formulations. This α-proteobacterium uses two independent flagellar systems to swim in liquid and viscous media. In our laboratory, we studied the synthesis and regulation of both flagellar systems, and here we show part of the regulatory cascade of the subpolar flagellum synthesis. Flagellar synthesis occurs in steps, each one controlled by different regulators. This process ensures the appropriate timing of the synthesis of different components. First, a master regulator initiates the signal cascade, then class II regulators control gene expression of the intermediate products and class III/IV regulators activate flagellum filament formation, the last product assembled.We present the characterization ofB. diazoefficiensmutants in two class II regulatory genes (flbDandfliX) and two class III regulatory genes (flaFandflbT), by measuring the transcription levels of the putative targets controlled by them and also the type of flagellins that they produced. Our results suggest that the regulation of the subpolar flagellum synthesis is independent from the lateral flagella and is controlled in a cell-cycle manner. These results fit with the model previously described inCaulobacter crescentusbut not withSalmonellamodel, as was thought in earlier studies