Ranjan Plant Physiology and Biochemistry Laboratory, Department of Botany, University of Allahabad, Allahabad, Uttar Pradesh 211002, India.
Plant Physiol Biochem. 2012 Dec;61:61-70. doi: 10.1016/j.plaphy.2012.09.005. Epub 2012 Sep 13.
Effects of low (UV-B(L); 0.1 μmol m(-2) s(-1)) and high (UV-B(H); 1.0 μmol m(-2) s(-1)) fluence rates of UV-B radiation on growth, oxidative stress and ascorbate-glutathione cycle (AsA-GSH cycle) were investigated in two cyanobacteria viz. Phormidium foveolarum and Nostoc muscorum under copper (2 and 5 μM) toxicity after 24 and 72 h of experiments. Cu at 2 and 5 μM and UV-B(H) irradiation decreased growth in both the organisms and the effect was more pronounced in N. muscorum. Superoxide radical (SOR) and hydrogen peroxide (H(2)O(2)) productions were significantly enhanced by Cu and UV-B(H) which was accompanied by accelerated lipid peroxidation (malondialdehyde; MDA) and protein oxidation (reactive carbonyl groups; RCG). The components of AsA-GSH cycle, i.e. ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascobate reductase (MDHAR) and dehydroascorbate reductase (DHAR) activities as well as total ascorbate and glutathione contents and their reduced/oxidized ratios were decreased considerably by Cu and UV-B(H). Further, combined treatments of Cu and UV-B(H) exacerbated damaging effects in both the cyanobacteria. Unlike UV-B(H), UV-B(L) irradiation rather than damaging cyanobacteria caused alleviation in Cu-induced toxicity by down-regulating the levels of SOR, H(2)O(2), MDA and RCG due to enhanced activity of APX, GR, MDHAR and DHAR, and contents of ascorbate and glutathione. Results revealed that UV-B radiation at low fluence rate (UV-B(L)) stimulated protective responses in both the organisms under Cu toxicity while UV-B(H) irradiation caused damage alone as well as together with Cu, and the components of AsA-GSH cycle play significant role in these responses.
低（UV-B(L)；0.1 μmol m(-2) s(-1)）和高（UV-B(H)；1.0 μmol m(-2) s(-1)）紫外线-B 辐射通量率对两种蓝藻（即 Phormidium foveolarum 和 Nostoc muscorum）生长、氧化应激和抗坏血酸-谷胱甘肽循环（AsA-GSH 循环）的影响，在铜（2 和 5 μM）毒性下进行了 24 和 72 小时的实验。2 和 5 μM 的 Cu 和 UV-B(H)辐射降低了两种生物的生长，而 N. muscorum 的影响更为明显。Cu 和 UV-B(H)显著增加了超氧自由基（SOR）和过氧化氢（H(2)O(2)）的产生，伴随着脂质过氧化（丙二醛；MDA）和蛋白质氧化（反应性羰基基团；RCG）的加速。AsA-GSH 循环的组成部分，即抗坏血酸过氧化物酶（APX）、谷胱甘肽还原酶（GR）、单脱氢抗坏血酸还原酶（MDHAR）和脱氢抗坏血酸还原酶（DHAR）的活性以及总抗坏血酸和谷胱甘肽的含量及其还原/氧化比，均因 Cu 和 UV-B(H)而显著降低。此外，Cu 和 UV-B(H)的联合处理加剧了两种蓝藻的损伤作用。与 UV-B(H)不同，UV-B(L)辐照对蓝藻没有造成损害，反而通过增强 APX、GR、MDHAR 和 DHAR 的活性以及抗坏血酸和谷胱甘肽的含量，下调 SOR、H(2)O(2)、MDA 和 RCG 的水平，从而减轻 Cu 诱导的毒性。结果表明，在 Cu 毒性下，低辐照度（UV-B(L)）的紫外线-B 辐射刺激了两种生物的保护反应，而 UV-B(H) 辐照单独以及与 Cu 一起造成损伤，AsA-GSH 循环的组成部分在这些反应中发挥重要作用。
