THE LOV HISTIDINE KINASE OF R. leguminosarum REGULATES THE SECRETION OF EPS AND FLAGELLAR PROTEINS

HERNÁN R. BONOMI; DIANA POSADAS; GASTON PARIS; MARIELA DEL CARMEN CARRICA; ROBERTO A. BOGOMOLNI; ANGELES ZORREGUIETA; FERNANDO A. GOLDBAUM

Tucumán, Argentina

Congreso; XLV Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación Bioquímica

Rhizobium leguminosarum is able to fix nitrogen and form symbiotic interactions with pea plants. Fixed nitrogen is made available to the plant which in turn provides carbon nutrients to the bacteria. Light, oxygen and voltage (LOV) domain are blue light photoreceptor modules that bind FMN as cofactor and undergo a photocycle upon illumination. In a previous work we have identified and characterized a LOV histidine kinase (LOV-HK) from the related bacteria Brucella. Searches in genomic databases of R. leguminosarum bv. viciae 3841 allowed us to identify a gene that encodes for a 345 amino acid protein that has a N-terminal LOV domain and C-terminal histidine kinase domain and lacks the central PAS domain present in Brucella LOV-HK. The production of exopolysaccharide (EPS) in R. leguminosarum is down regulated by light and this effect is not observed a LOV-HK mutant strain. The flagellin proteins are down regulated in R. leguminosarum grown in light as compared with the bacteria grown in the dark. The pattern of flagellar proteins from the R. leguminosarum LOV-HK mutant was not different between light and dark and it is similar to the one of R. leguminosarum wt cells grown in the dark. Using bacterial twohybrid assay we indentified two single domain response regulators as partners of LOV-HK protein. These results confirm that LOV-HK is working as blue light photoreceptor in Rhizobium.