Construction and use of GFP reporter vectors for analysis of cell-type-specific gene expression in Nostoc punctiforme

Two transcriptional reporter shuttle vectors were constructed for the filamentous cyanobacterium Nostoc punctiforme using the green fluorescence protein (GFP) reporter. Both the ampicillin-and kanamycin-resistant versions of the plasmid allow promoters to be directionally cloned into a multiple cloning site preceding a promoterless gfp gene using an Escherichia coli host. The ability of the self-replicating shuttle plasmids to report cell-type-specific gene expression in N. punctiforme was tested by cloning promoters expressed in normal vegetative cells, nitrogen-fixing heterocysts and spore-like akinetes. A P-psaC reporter gene fusion was expressed in vegetative cells and not in heterocysts, whereas GFP driven from P-hetR was found highly expressed in heterocysts. GFP expression driven by the promoter for the N. punctiforme homologue of the akinete-specific gene avaK was expressed in developing akinetes. Decreased expression of GFP from the P-psaC reporter in hormogonia was also observed. The results demonstrate the utility of these GFP vectors to study cell-type-specifie gene expression in differentiating filamentous cyanobacteria. (C) 2004 Elsevier B.V. All rights reserved.