Alterations in the structure of phycobilisomes of the cyanobacterium,Spirulina platensis in response to enhanced Na+ level

Incubation of Spirulina platensis at enhanced Na⁺ concentrations resulted in 30% increased intracellular accumulation of Na⁺ ions. This accumulation of Na⁺ ions intracellularly altered the phycobilisome organization as revealed by transmission electron microscopic data and changes in the absorption spectrum. The room temperature emission peak at 638 nm in the control sample was blue-shifted by 7 nm in the treated samples suggesting phycobilisome disorganization. SDS-PAGE of phycobilisome polypeptides showed a significant increase in a 66.2 kDa polypeptide. This is the first report that the enhanced concentration of intracellular Na⁺ ion alters the structure of the phycobilisome in S. platensis. This revised version was published online in November 2006 with corrections to the Cover Date.     

Engineered BcZAT12 gene mitigates salt stress in tomato seedlings

In salt-prone areas, plant growth and productivity is adversely affected. In the present study, the ZT1-ZT6 transgenic tomato lines having BcZAT12 gene under the regulatory control of the stress inducible Bclea1 promoter were exposed to three salinity levels (50, 100 and 200 mM) at the four leaf stage for 10 days. The transgenic lines showed improved growth in stem height, leaf area, root length and shoot length under saline conditions, as compared to control. Moreover, ZT1 and ZT5 lines showed lower electrolyte leakage and decreased hydrogen peroxide formation, in combination with elevated relative water content, proline and chlorophyll levels. The enzyme activity of catalase was also enhanced in ZT1 and ZT5. These results poses the present lines as an attractive alternative for tomato cultivation in salinity-affected areas.Keyword: Abiotic stress, Antioxidant, Oxidative stress, Salinity, Seedlings, Tomato     

Differential Regulation of Nitrogen Metabolism in the Wild Type and the High-Light-Tolerant Mutant Cells of Anacystis nidulans

The glutamine synthetase activity in the wild type and high-light-tolerant mutant of Anacystis exhibited differential response to the increasing light intensity (2–40 W/m²). As evident from the results, the glutamine synthetase (GS) activity in the wild type is more dependent on respiration, whereas the GS enzyme in the mutant cells derived its carbon and energy from photosynthesis. Further, results revealed that the reduced GS activity in the wild-type cells under the high-light stress was accompanied by high aspartate amino transferase (AST/GOT) activity and low alanine amino transferase (ALT/GPT) activity. On the contrary, high GS activity in the mutant cells was accompanied by low AST/GOT enzyme activity and high ALT/GPT activity. It was inferred that mutant and wild-type cells adapt to the high-light stress by different mechanisms.     

Decolorization of triphenylmethane dyes by the bird's nest fungus Cyathus bulleri

Decolorization of three triphenylmethane dyes by three bird's nest fungi—Cyathus bulleri, C. stercoreus, and C. striatus—was studied. Cyathus bulleri was found to be the most efficient in decolorization as demonstrated by the disappearance of the dyes from cultures, monitored by decreases in absorbance. Growth of the Cyathus spp. was not affected by the presence of dyes in the cultures. Decolorization of dyes was also observed with extracellular culture filtrates, indicating exocellular activity. Laccase activity, tested in replicate cultures, was found to be maximum during the decolorization period. Nitrogen in the medium had no effect on decolorization.