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Abstract
For examining how UV-B radiation alters the proteome of the N2-fixing cyanobacterium, Anabaena L31, we extracted proteins from cultures irradiated with UV-B + white light and controls (white light irradiated) and analyzed the proteins using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). Twenty one proteins, including two hypothetical proteins (HPs) were identified and placed in eight functional categories. However several of the proteins were housekeeping proteins involved in key metabolic processes such as carbon, amino acid biosynthesis and energy metabolism, certain proteins seem to have a role in stress (antioxidative enzymes), translation, cellular processes and reductases. Two novel HPs (all3797 and all4050) were characterized in detail. These two were over-expressed after UV-B irradiation and characterized as FAS 1 (all3797) and PRC barrel-like (all4050) proteins. Bioinformatics analysis revealed that the genes of both the HPs have promoter regions as well as transcription binding sites in their upstream region (UTR). Promoters present in all3797 genes suggest their crucial role against UV-B and certain other abiotic stresses. To our knowledge these novel proteins have not been previously reported in any Anabaena strains subjected to UV-B stress. Although we have focused our study on a limited number of proteins, results obtained shed light on the highly complicated but poorly studied aspect of UV-B radiation-mediated changes in the proteome and expression of proteins in cyanobacteria.
Highlights
While sunlight provides the energy for life, the ultraviolet-B (UV-B; 280–315 nm) and long-wavelength UV light (UV-A; 315– 400 nm) components of the solar spectrum are harmful to many organisms
EFFECTS OF UV-B RADIATION ON GROWTH AND SURVIVAL Before assessing the effects of UV-B radiation + white light on proteome changes, we examined its effect on percentage survival and chlorophyll-a content in Anabaena L31
PREDICTION AND LOCALIZATION OF FUNCTIONAL DOMAIN, MOTIF ANALYSIS, AND SEQUENCE HOMOLOGY OF HYPOTHETICAL PROTEINS As both the hypothetical proteins (HPs) were always induced under UV-B stress and such proteins have not been reported previously from cyanobacteria, we focused our studies on these two proteins
Summary
While sunlight provides the energy for life, the ultraviolet-B (UV-B; 280–315 nm) and long-wavelength UV light (UV-A; 315– 400 nm) components of the solar spectrum are harmful to many organisms. Cyanobacteria are photosynthetic prokaryotes with an evolutionary history that precedes the development of atmospheric ozone protection. They grow in a wide range of diverse and extreme habitats such as hot springs, arctic regions, desert soils, and rocky surfaces (Whitton and Potts, 2000). They show considerable metabolic plasticity and, besides assimilating CO2 and O2, certain species assimilate N2 and H2 (Stewart, 1980). Studies conducted so far suggest that the deleterious effects of UV-B radiation in cyanobacteria are in part due to the direct effects on membrane components, growth and survival, motility, pigmentation, uptake of CO2, photosynthetic apparatus the reaction center of photosystem II, RuBisCO, N2 fixation, DNA, proteins, and enzymes (Wilson et al, 1995; Kumar et al, 2003, 2004; Singh et al, 2010, 2013)
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