title: Ultraviolet radiation and cyanobacteria.
abstract: Cyanobacteria are the dominant photosynthetic prokaryotes from an ecological, economical, or evolutionary perspective, and depend on solar energy to conduct their normal life processes. However, the marked increase in solar ultraviolet radiation (UVR) caused by the continuous depletion of the stratospheric ozone shield has fueled serious concerns about the ecological consequences for all living organisms, including cyanobacteria. UV-B radiation can damage cellular DNA and several physiological and biochemical processes in cyanobacterial cells, either directly, through its interaction with certain biomolecules that absorb in the UV range, or indirectly, with the oxidative stress exerted by reactive oxygen species. However, cyanobacteria have a long history of survival on Earth, and they predate the existence of the present ozone shield. To withstand the detrimental effects of solar UVR, these prokaryotes have evolved several lines of defense and various tolerance mechanisms, including avoidance, antioxidant production, DNA repair, protein resynthesis, programmed cell death, and the synthesis of UV-absorbing/screening compounds, such as mycosporine-like amino acids (MAAs) and scytonemin. This study critically reviews the current information on the effects of UVR on several physiological and biochemical processes of cyanobacteria and the various tolerance mechanisms they have developed. Genomic insights into the biosynthesis of MAAs and scytonemin and recent advances in our understanding of the roles of exopolysaccharides and heat shock proteins in photoprotection are also discussed.
authors.affiliation: Institute of Green Environmental Research, Incheon National University, 7-46 Songdo-dong, Yeonsu-gu, Incheon 406-840, Republic of Korea.
authors.forename: Rajesh Prasad
authors.initials: RP
authors.lastname: Rastogi
authors.affiliation: Laboratory of Photobiology and Molecular Microbiology, Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi 221005, India.
authors.forename: Rajeshwar P
authors.initials: RP
authors.lastname: Sinha
authors.affiliation: Anti-aging Research Institute of BIO-FD&C Co., Ltd., Phytomecca Co., Ltd., Pilot Plant 7-50, Songdo-dong, Incheon 406-840, Republic of Korea.
authors.forename: Sang Hyun
authors.initials: SH
authors.lastname: Moh
authors.affiliation: South Sea Environment Research Department, Korea Institute of Ocean Science and Technology, Geoje 656-830, Republic of Korea.
authors.forename: Taek Kyun
authors.initials: TK
authors.lastname: Lee
authors.affiliation: Institute of Green Environmental Research, Incheon National University, 7-46 Songdo-dong, Yeonsu-gu, Incheon 406-840, Republic of Korea.
authors.forename: Sreejith
authors.initials: S
authors.lastname: Kottuparambil
authors.affiliation: Department of Marine Science, Incheon National University, 12-1 Songdo-dong, Yeonsu-gu, Incheon 406-840, Republic of Korea.
authors.forename: Youn-Jung
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Department of Marine Science, Incheon National University, 12-1 Songdo-dong, Yeonsu-gu, Incheon 406-840, Republic of Korea.
authors.forename: Jae-Sung
authors.initials: JS
authors.lastname: Rhee
authors.affiliation: Department of Chemistry, Incheon National University, 12-1 Songdo-dong, Yeonsu-gu, Incheon 406-840, Republic of Korea.
authors.forename: Eun-Mi
authors.initials: EM
authors.lastname: Choi
authors.affiliation: School of Marine Science & Engineering, Plymouth University, Plymouth, Devon PL4 8AA, United Kingdom.
authors.forename: Murray T
authors.initials: MT
authors.lastname: Brown
authors.affiliation: Neue Str. 9, 91096 Möhrendorf, Germany.
authors.forename: Donat-Peter
authors.initials: DP
authors.lastname: Häder
authors.affiliation: Institute of Green Environmental Research, Incheon National University, 7-46 Songdo-dong, Yeonsu-gu, Incheon 406-840, Republic of Korea; Department of Marine Science, Incheon National University, 12-1 Songdo-dong, Yeonsu-gu, Incheon 406-840, Republic of Korea. Electronic address: hanalgae@hanmail.net.
authors.forename: Taejun
authors.initials: T
authors.lastname: Han
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D000458:Cyanobacteria / Q000378:metabolism / Q000528:radiation effects*; D003512:Cyclohexanones / Q000737:chemistry / Q000378:metabolism; D004249:DNA Damage / Q000528:radiation effects; D006360:Heat-Shock Proteins / Q000378:metabolism; D007211:Indoles / Q000737:chemistry / Q000378:metabolism; D010636:Phenols / Q000737:chemistry / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D013312:Stress, Physiological / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D000975:Antioxidants; D001426:Bacterial Proteins; D003512:Cyclohexanones; D006360:Heat-Shock Proteins; D007211:Indoles; D010636:Phenols; D011135:Polysaccharides, Bacterial; C083368:scytonemin