Abstract
The filamentous heterocystous cyanobacterium Anabaena variabilis harbors three genetically distinct nitrogenases. The conventional Mo-nitrogenase, encoded by nif1, expresses in the absence of a fixed nitrogen source when Mo is available. The V-nitrogenase encoded by vnf accumulates under Mo deficient condition in the presence of V, whereas, nif2 coding for another Mo-nitrogenase is expressed in vegetative cells only, under anaerobic condition. We report here the expression of the nif1 and vnf in heterocysts. Using reporter genes gfp and bfp, we have constructed 3 kinds of transcriptional fusion nif1-gfp-Ω, vnf-bfp-C.K3 and nif1-gfp-Ω-vnf-bfp-C.K3 in the shuttle vector pRL25C. The resulting vectors were transformed into the host cell with the help of conjugative plasmid RP4 by triparental mating method. The in situ expression of nif1 and vnf was detected by observing the over-expression of GFP and BFP under the regulation of a variety of environmental factors.
