Oxidative damage to chloroplasts from Chlorella vulgaris exposed to ultraviolet‐B radiation

Abstract

Malanga, G., Calmanovici, G. and Puntarulo, S. 1997, Oxidative damage to chloroplasts from Chlorella vuigaris exposed to ultraviolet-B radiation. -Physiol. Plant. 101:455-462.Upon UV-B irradiation, Chlorella vuigaris cells and isolated chloroplasts increased in size and starch accumulation. Photosynthetic capacity and chlorophyll content of chloroplasts isolated from irradiated algae decreased by 72 and 66%, as compared to chloroplasts isolated from control cells. Dihydrorhodamine 123 conversion to rhodamine 123 was used as a sensitive method for detection of peroxide (presumably hydrogen peroxide) formation in isolated chloroplasts. The accumulation of rhodamine 123 is higher in irradiated than in nonirradiated chloroplasts and the increased accumulation of rhodamine 123 depended on the UV-B dose. Quantitation of alkyl radical-EPR signals in chloroplasts indicated that UV-B exposure significantly increased radical content in the membranes. The content of an oxidized DNA base (8hydroxy-2'-deoxyguanosine) in chloroplasts was increased by 72 and 175% after irradiation of the algal culture with 17.3 and 42.6 kJ m~", respectively. The chioropiastic activity of superoxide dismutase decreased by 50% as compared with control values after irradiation with 42.6 kJ m"" and no changes in ascorbate peroxidase activity and ascorbic acid content were detected at the irradiation doses tested. The y5-carotene content in chloroplasts was not affected by the irradiation, but the a-tocopherol content increased approximately 4-fold after UV-B irradiation. The results suggest that oxidative damage related to UV-B exposure is responsible for alterations in chloroplasts function and integrity, and that an antioxidant response is triggered in chloroplasts through an increase in a-tocopherol content.

High‐light‐induced Changes on Photosynthesis, Pigments, Sugars, Lipids and Antioxidant Enzymes in Freshwater (Nostoc spongiaeforme) and Marine (Phormidium corium) Cyanobacteria

“…Although formation of these compounds is a normal part of the metabolism, excessive production can cause damage to DNA, proteins and lipids (38). UV-B radiation is known to cause oxidation of membrane lipids (39). He and Hader (40) observed induction of reactive oxygen species under in vivo condition due to UV-B stress in the cyanobacterium Anahaena, which was further enhanced when photochemical reactions of PS I1 were impaired.…”

NUTRIENT LIMITATION AND HIGH IRRADIANCE ACCLIMATION REDUCE PAR AND UV‐INDUCED VIABILITY LOSS IN THE ANTARCTIC DIATOM CHAETOCEROS BREVIS (BACILLARIOPHYCEAE)1

“…The reaction center of the PSII protein-pigment complex and enzymes from the Calvin cycle are highly sensitive to ROS. Additional UVB exposure increases ROS formation and damage to PSII, whereas reduction of the RUBISCO pool and DNA damage are also reported (Schofield et al 1995, Lesser 1996a,b, Lesser et al 1996, Malanga et al 1997, Rijstenbil et al 2000, Rijstenbil 2001, Buma et al 2001. Because UVB coincides with high UVA and PAR, UVB-induced stress always co-occurs with UVA and PAR stress.…”

UV-B Radiation Suppresses the Growth and Antioxidant Systems of Two Marine Microalgae,Platymonas subcordiformis(Wille) Hazen andNitzschia closterium(Ehrenb.) W. Sm

“…Harmful effects of solar radiation, mainly UV-B (280−315 nm), on principal cell constituents such as nucleic acids, pigments, proteins and lipids are the result of photochemical reactions, some of which involve active oxygen species (Ishida et al 1997). Because active oxygen production is induced by UV light and strong irradiance,oxidative stress might be an important consequence of temporary exposure to solar radiation at the water surface (Malanga et al 1997). Oxidative stress is potentially experienced by all aerobic life when anti-oxidant defenses are overcome by pro-oxidant forces.…”