Differential responses to cadmium induced oxidative stress in marine macroalga Ulva lactuca (Ulvales, Chlorophyta)

Abstract

This study describes various biochemical processes involved in the mitigation of cadmium toxicity in green alga Ulva lactuca. The plants when exposed to 0.4 mM CdCl(2) for 4 days showed twofold increase in lipoperoxides and H(2)O(2) content that collectively decreased the growth and photosynthetic pigments by almost 30% over the control. The activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione peroxidase (GPX) enhanced by twofold to threefold and that of catalase (CAT) diminished. Further, the isoforms of these enzymes, namely, Mn-SOD (approximately 85 kDa), GR (approximately 180 kDa) and GPX (approximately 50 kDa) responded specifically to Cd(2+) exposure. Moreover, the contents of reduced glutathione (3.01 fold) and ascorbate (1.85 fold) also increased substantially. Lipoxygenase (LOX) activity increased by two fold coupled with the induction of two new isoforms upon Cd(2+) exposure. Among the polyunsaturated fatty acids, although n - 3 PUFAs and n - 6 PUFAs (18:3n - 6 and C18:2n - 6) showed relatively higher contents than control, the latter ones showed threefold increase indicating their prominence in controlling the cadmium stress. Both free and bound soluble putrescine increased noticeably without any change in spermidine. In contrast, spermine content reduced to half over control. Among the macronutrients analysed in exposed thalli, the decreased K content was accompanied by higher Na and Mn with no appreciable change in Ca, Mg, Fe and Zn. Induction of antioxidant enzymes and LOX isoforms together with storage of putrescine and n - 6 PUFAs in cadmium exposed thallus in the present study reveal their potential role in Cd(2+) induced oxidative stress in U. lactuca.

Effects of Cadmium on Growth, Photosynthetic Pigments, Photosynthetic Performance, Biochemical Parameters and Structure of Chloroplasts in the Agarophyte <i>Gracilaria domingensis</i> (Rhodophyta, Gracilariales)

“…The increased GR activity observed in G. domingensis after cadmium exposure could be related to the increased antioxidant defenses that result from Cd-induced oxidative stress. These results agree with those of Kumar et al [5], who demonstrated that the green alga Ulva lactuca also increased in GR activity after exposure to cadmium.…”

“…Heavy metals affect all biological organisms, especially those in the aquatic ecosystem, in many important ways. Several studies have shown effects such as the decrease of macroalgae growth rates [2], increased activities of glutathione reductase [5], changes in photosynthetic pigments [1,6] and photosynthetic efficiency [2,6], as well as an increase in total proteins and lipid contents [1]. Finally, some reports have shown changes in the ultrastructure of the red algae Audouinella savina (F. S. Collins) Woelkerling [7] and Ceramium ciliatum (J. Ellis) Ducluzeau [8], Hypnea musciformis (Wulfen) Lamouroux [6]; the green algae Dunaliella minuta Lerche [9], Enteromorpha flexuosa (Wulfen) J. Agardh [10], Euglena gracilis Klebs [1], and the brown algae Padina gymnospora (Kützing) Sonder [11].…”

Effect of Cadmium onArabidopsis ThalianaMutants Tolerant to Oxidative Stress

“…We found that atr1, atr2, atr7, atr8 and atr9 showed less oxidative damage on cadmium compared to their background loh2 and the other lines (Fig. 2) wich correspond to our observation about phenotypic effect of cadmium on these mutants.. An induction of lipid peroxidation upon cadmium treatment was reported for Arabidopsis wild type seedlings, Arabidopsis plants, green alga Ulva lactuca, and in tomato plants respectively (50,30,55,4), while Gonçalves et al (22) demonstrated that MDA levels decreased under low concentartions of cadmium in cuccumber seedlings. …”

“…Gonçalves et al (22) and Sandalio et al (51) demonstrated the reduction of total dry weight in cuccumber seedlings and pea plants respectively, while in wheat seedlings cadmium has an opposite effect (34) and low concentrations of cadmium slightly increased the chlorophyll content in barley seedlings (29). The reduction of growth upon cadmium treatment was observed in Arachis hypogaea seedlings (11) (55) and in green alga Ulva lactuca accompanied with decrease in photosynthetic pigments (30). …”

“…Thus, low cadmium concentrations and short periods of treatment lead to increase in antioxidative enzyme activities (58,22,23,4), while longer periods of treatment induce a reduction in antioxidant activities (51,46). CAT activity was reduced by Cd 2+ in pea (12,46) and pine roots (54), pea leaves (51), sunflower (32) and Arabidopsis leaves (6) and seedlings (50) and in alga Ulva lactuca (30). The opposite effect was observed in radish roots (63), Spartina densiflora (37), Arachis hypogaea seedlings (11) and in tobacco plants which overexpress a soybean OAcetylserine (thyol) lyase (OASTL, EC 2.5.1.47) (41).…”