Isolation and partial characterization of a Synechococcus sp. PCC 7942 mutant resistant to a natural herbicide

• Published in: Plant science (Limerick) 2003-10, Vol.165 (4), p.785-791
• Main Authors: Ray, Soma, Shrivastava, Rahul, Bagchi, Suvendra N.
• Format: Article
• Language: English
• Subjects: Action of physical and chemical agents on bacteria; Bacteriology; Biological and medical sciences; Cyanobacteria ( Synechococcus sp. PCC 7942); Fundamental and applied biological sciences. Psychology; Herbicide resistance; Microbiology; Oxidative stress; PsbO (manganese stabilizing protein); Synechococcus; Water oxidizing complex
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/S0168-9452(03)00272-3

Mutants of Synechococcus sp. PCC 7942 resistant to a natural photosystem II-inhibitory herbicide, oscillatorin, were isolated from a random mutagenesis with N-methyl- N′-nitro- N-nitrosoguanidine. These mutants had elevated growth rates and photosynthetic activity relative to the wild type, and exhibited a high degree of resistance to phenolic-type but not to the atrazine-class of herbicides. Examination of dichlorophenol indophenol photo-reductions in the wild type with water and diphenyl carbazide electron donors revealed that oscillatorin preferentially affects the water oxidizing complex. A comparative analysis of the content of photosynthesis associated proteins revealed that in one such mutant designated Osc r1, PsbO, the manganese stabilizing protein, was highly expressed even under manganese and calcium deficient growth conditions. The amount of PsbA was also higher in the mutant. Solubilizing Mn from the water oxidizing complex was less inhibitory to photosystem II activity in mutant Osc r1. While wild type showed significant photoinhibition in the presence of lincomycin, mutant Osc r1 was much more resistant. Our results suggest that over-expression of PsbO in the mutant Osc r1 and related stability and integrity of water oxidizing complex confers resistance to the oxidative stress caused by oscillatorin.