Nitrate metabolism plays an important role in bacterial physiology. During the interaction of plant pathogenic bacteria with its hosts, bacteria face variable conditions with respect to nitrate availability. Perception mechanisms through the chemosensory pathway drive the entry and control the colonization of plant host in phytopathogenic bacteria. In this work, the identification and characterization of the NIT sensor domain containing chemoreceptor of Dickeya dadantii 3937 (Dd3937) allowed us to unveil the key role of nitrate sensing not only for the entry to the plant apoplast through wounds but also for the infection success. We have determined the specificity of this chemoreceptor to bind nitrate and nitrite with a slight ligand preference for nitrate. Gene expression analysis showed that nitrate perception controls not only the expression of nitrate reductase genes involved in respiratory and assimilatory metabolic processes, but also the expression of gyrA, hrpN and bgxA, three well known virulence determinants in Dd3937.

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