Molecular characterization of hetR gene from Cylindrospermum stagnale A 1345 isolated from arid soil

HetR gene is a key regulator of heterocyst differentiation in filamentous cyanobacteria. It has been previously isolated and characterized from heterocystous cyanobacterium like Anabaena that has intercalary heterocysts and from non-heterocystous cyanobacteria like Trichodesmium and Symploca PCC 8002. This study reports the characterization of hetR gene from Cylindrospermum stagnale A1345, a cyanobacterium containing only terminal heterocysts. The expression profile of hetR gene and its correlation with the nitrogenase enzyme activity and heterocyst differentiation after nitrogen depletion has been investigated. Genomic analysis was carried out for copy number determination of the gene and northern blots for transcript profile. Immunoblot analysis of the Fe-protein subunit of nitrogenase enzyme complex at different time intervals revealed that the protein was detectable only around 24 hrs after nitrogen depletion and transcript levels of hetR gene correlated with the nitrogenase enzyme activity. Proheterocysts were observed at 24 hrs and fully developed heterocysts were found between 36 hrs and 48 hrs.