Characterization of four superoxide dismutase genes from a filamentous cyanobacterium

Abstract

By using an oligonucleotide probe constructed from a conserved region of amino acids located in the carboxyl-terminal end of superoxide dismutase (SOD) proteins, four SOD genes were cloned from the cyanobacterium Plectonema boryanum UTEX 485. One of these genes, designated sodB, encoded an FeSOD enzyme, while the remaining three genes, designated sodA1, sodA2, and sodA3, encoded MnSOD enzymes. To investigate the expression of these four genes, total cellular RNA was isolated from P. boryanum UTEX 485 cells grown under various conditions and RNA gel blot analysis was carried out. Results indicated that sodB and sodA1 were constitutively expressed, although sodB expression was partially repressed in cells grown under conditions of iron stress. sodA2 transcripts, which were not detectable in control cells, accumulated to high levels in cells treated with methyl viologen or in cells grown under conditions of iron or nitrogen stress. However, under microaerobic conditions, iron and nitrogen stress failed to induce sodA2, indicating that multiple factors affect the regulation of sodA2. While discrete transcripts were not detected for sodA3, hybridization was observed under a number of conditions, including those which increased the accumulation of sodA2 transcripts. Additionally, there were high levels of the sodA3 transcript detected in a P. boryanum UTEX 485 mutant strain resistant to methyl viologen treatment.

The Iron Superoxide Dismutase from the Filamentous Cyanobacterium Nostoc PCC 7120

“…Table II lists twelve cyanobacterial species or strains where sequences of the whole or nearly complete genome are available. Included are also data from P. boryanum (44). All filamentous cyanobacteria seem to contain a membrane-bound MnSOD, whereas unicellular cyanobacteria only have a cytosolic superoxide dismutase with the exception of Gloeobacter violaceus and T. elongatus, which also have a membrane-bound MnSOD.…”

“…Superoxide dismutase activity was also measured in vegetative cells and heterocysts of A. cylindrica, with heterocysts having lower levels of activity (43). Four genes of SOD, one coding for an FeSOD and three coding for MnSOD, were characterized in P. boryanum (44). As well a CuZnSOD was identified in the marine cyanobacterium Synechococcus WH7803 (45).…”

Differential Expression and Localization of Mn and Fe Superoxide Dismutases in the Heterocystous Cyanobacterium Anabaena sp. Strain PCC 7120

“…Apparently, the presence of two kinds of Sod in most of the cyanobacteria is advantageous in adapting metal concentration fluctuations in their environments. So far, only one copy of sodB gene is present in all cyanobacteria studied (8,19,26). The assignment of the cyanobacterial sodB genes was mostly based on their primary sequences (19,26).…”

“…strain PCC 7120 has recently been determined (www.cyanosite.bio.purdue.edu). A BLAST search based on its sodB gene revealed the presence of another sod gene, which showed a high homology to the sodA2 gene from Plectonema boryanum (8). No Cu,Zn-type sod gene was found in the Anabaena sp.…”

Manganese Deficiency in Chlamydomonas Results in Loss of Photosystem II and MnSOD Function, Sensitivity to Peroxides, and Secondary Phosphorus and Iron Deficiency

“…Interestingly, cell fractionation experiments suggest that the major MnSOD isoform shows dual localization to both the mitochondria and chloroplast, indicating that this isoform may cover the loss of the chloroplast FeSOD. The replacement of an FeSOD by a MnSOD has been observed in bacteria and suggested as well in diatoms that show an increased requirement for manganese in an Fe-deficient growth environment (Privalle and Fridovich, 1993;Campbell and Laudenbach, 1995;Peers and Price, 2004).…”