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Antioxidant response to salinity stress in freshwater and marine Bangia (Bangiales, Rhodophyta)

Wang, Wen Jun, Li, Xiao Lei, Zhu, Jian Yi, Liang, Zhou Rui, Liu, Fu Li, Sun, Xiu Tao, Wang, Fei Jiu, Shen, Zong Gen
Aquatic botany 2019 v.154 pp. 35-41
Bangia, acclimation, antioxidant activity, aquatic plants, botany, catalase, enzyme activity, freshwater, glutathione-disulfide reductase, hydrogen peroxide, hypersalinity, peroxidase, photosystem II, salt stress, seawater, superoxide anion, superoxide dismutase
Bangia is an ancient and genetically diverse red algae genus, containing one freshwater species. It has been reported that freshwater Bangia acclimates seawater and marine Bangia survives freshwater after gradual adaptation or one to several steps transfer. However, little is known about the acclimation mechanism. The present study revealed that marine Bangia tolerated moderate hyposalinity and freshwater Bangia endured seawater as indicated by the maximum quantum yield of PSII (Fv/Fm). Little reduction of Fv/Fm occurred in 100% seawater treated freshwater Bangia and there was no significant difference of Fv/Fm under different hypersalinity on the 5th day. The O2.− levels were lower than control while accumulation of H2O2 was observed in the hypersalinity-treated freshwater Bangia and hyposalinity-treated marine Bangia. There was a correlation between O2.− and superoxide dismutase induction, resulting in effective removal of O2.−. Mono- to multi-phasic induction of peroxidase occurred in hyposaline stressed marine Bangia and induction of catalase was present in hypersaline stressed freshwater Bangia. The Fv/Fm reduction was the highest in 100% freshwater-treated marine Bangia, while neither peroxidase nor catalase activity was enhanced. The glutathione reductase activities exhibited triphasic induction in 100% freshwater-treated marine Bangia and 100% seawater-treated freshwater Bangia, indicating that glutathione reductase played important roles under highly saline stress. In sum, the antioxidant enzymes activities were peroxidase > superoxide dismutase > glutathione reductase > catalase. The H2O2 and antioxidases was less induced and Fv/Fm was less reduced in seawater-stressed freshwater Bangia than in freshwater-stressed marine Bangia in most cases. The results suggested a higher capacity of freshwater Bangia endurance to seawater than marine Bangia endurance to freshwater.