Changes in ultrastructure and responses of antioxidant systems of algae (Dunaliella salina) during acclimation to enhanced ultraviolet-B radiation.
Because of depletion of the stratospheric ozone layer, levels of solar ultraviolet-B (UV-B) radiation (280-315 nm), which penetrates the water column to an ecologically-significant depth, are increasing. In order to assess changes in ultrastructure and responses of antioxidant systems of algae during acclimation to enhanced ultraviolet-B radiation, Dunaliella salina was treated with higher dose of UV-B radiation (13.2 kJm(-2) d(-1) dose) in this study. As compared to the control panel (8.8 kJm(-2) d(-1)), the treatment D. salina had many changes in ultrastructures: (1) thylakoids became swelled, and some of them penetrated into the pyrenoid; (2) lipid globules accumulated; (3) the amounts of starch grains increased; (4) cristae of mitochondria disintegrated; (5) inclusions in vacuoles reduced; and (6) cisternae of Golgi dictyosomes became loose and swollen. Enhanced UV-B irradiation also induced different responses of the antioxidant systems in D. salina: (1) contents of TBARS (thiobarbituric acid reacting substance) and H(2)O(2) increased significantly (p<0.05); (2) levels of MAAs (mycosporine-like amino acids) increased at the beginning and subsequently decreased, and finally they leveled off at lower values; (3) there were not apparent variations for carotenoid contents, and contents of chlorophyll a presented a trend of initial increase and ultimate decrease; (4) both ascorbate and glutathione contents increased significantly (p<0.05); and (5) for the enzyme activities, POD activities increased remarkably (p<0.05), and SOD activities declined apparently (p<0.05), and CAT activity in D. salina had slight variations (p>0.05). In addition, growth curve displayed that enhanced UV-B radiation prominently inhibited increase of cell concentration when compared with control panel (p<0.05). Our results indicated that enhanced UV-B radiation caused ultrastructural changes of D. salina and induced different responses of antioxidant systems in D. salina.
Tian
Jiyuan
J
College of Food Science and Engineering, Qingdao Agricultural University, Qingdao 266109, PR China.
Yu
Juan
J
D000064:Acclimatization / Q000528:radiation effects*; D000975:Antioxidants / Q000378:metabolism*; D001205:Ascorbic Acid / Q000378:metabolism; D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000460:Chlorophyta / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D005978:Glutathione / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014466:Ultraviolet Rays
D000975:Antioxidants; D017392:Thiobarbituric Acid Reactive Substances; D002734:Chlorophyll; D002338:Carotenoids; D006861:Hydrogen Peroxide; D009195:Peroxidase; D013482:Superoxide Dismutase; D005978:Glutathione; D001205:Ascorbic Acid