Diversity of nickel ligands in nodule cytosol, nickel transport, and expression of a nickel-dependent enzyme in endosymbiotic bacteria as affected by the legume host

Abstract

Provision of metals to endosymbiotic bacteria represents a potential limitation for metalloenzyme synthesis inside legume nodules. Metal ions are usually bound to organic ligands in the cell cytoplasm, and the nature of such metal-ligand complexes might affect metal availability. We have observed a strong effect of the legume host on hydrogenase synthesis when the same Rhizobium leguminosarum bv. viciae strain establishes a symbiotic interaction with pea (Pisum sativum) or lentil (Lens sculenta) plants. These data, along with the different phenotypes of mutants altered in nickel (Ni) transport in these hosts, suggest a role for the chemical form of Ni on metal provision to the bacteroid. The biochemical analysis of cytosolic fractions of pea and lentil nodules has revealed the different nature and concentration of organic ligands chelating Ni in these host