Uzilday Baris, Turkan Ismail, Ozgur Rengin, Sekmen Askim H
Department of Biology, Faculty of Science, Ege University, Bornova, 35100 Izmir, Turkey.
J Plant Physiol. 2014 Jan 1;171(1):65-75. doi: 10.1016/j.jplph.2013.06.016. Epub 2013 Aug 3.
In the present study, we aimed to elucidate how strategies of reactive oxygen species (ROS) regulation and the antioxidant defense system changed during transition from C₃ to C₄ photosynthesis, by using the model genus Flaveria, which contains species belonging to different steps in C₄ evolution. For this reason, four Flaveria species that have different carboxylation mechanisms, Flaveria robusta (C₃), Flaveria anomala (C₃-C₄), Flaveria brownii (C₄-like) and Flaveria bidentis (C₄), were used. Physiological (growth, relative water content (RWC), osmotic potential), and photosynthetical parameters (stomatal conductance (g(s)), assimilation rate (A), electron transport rate (ETR)), antioxidant defense enzymes (superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductases(GR)) and their isoenzymes, non-enzymatic antioxidant contents (ascorbate, glutathione), NADPH oxidase (NOX) activity, hydrogen peroxide (H₂O₂) content and lipid peroxidation levels (TBARS) were measured comparatively under polyethylene glycol (PEG 6000) induced osmotic stress. Under non-stressed conditions, there was a correlation only between CAT (decreasing), APX and GR (both increasing) and the type of carboxylation pathways through C₃ to C₄ in Flaveria species. However, they responded differently to PEG-induced osmotic stress in regards to antioxidant defense. The greatest increase in H₂O₂ and TBARS content was observed in C₃ F. robusta, while the least substantial increase was detected in C₄-like F. brownii and C₄ F. bidentis, suggesting that oxidative stress is more effectively countered in C₄-like and C₄ species. This was achieved by a better induced enzymatic defense in F. bidentis (increased SOD, CAT, POX, and APX activity) and non-enzymatic antioxidants in F. brownii. As a response to PEG-induced oxidative stress, changes in activities of isoenzymes and also isoenzymatic patterns were observed in all Flaveria species, which might be related to ROS produced in different compartments of cells.
在本研究中，我们旨在通过使用黄顶菊属这一模式属来阐明从C₃光合作用向C₄光合作用转变过程中活性氧（ROS）调节策略和抗氧化防御系统是如何变化的，该属包含属于C₄进化不同阶段的物种。因此，我们使用了四种具有不同羧化机制的黄顶菊属物种，即粗壮黄顶菊（C₃）、异型黄顶菊（C₃ - C₄）、布朗氏黄顶菊（类C₄）和二齿黄顶菊（C₄）。在聚乙二醇（PEG 6000）诱导的渗透胁迫下，对生理参数（生长、相对含水量（RWC）、渗透势）、光合参数（气孔导度（g(s)）、同化率（A）、电子传递速率（ETR））、抗氧化防御酶（超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POX）、抗坏血酸过氧化物酶（APX）、谷胱甘肽还原酶（GR））及其同工酶、非酶抗氧化剂含量（抗坏血酸、谷胱甘肽）、NADPH氧化酶（NOX）活性、过氧化氢（H₂O₂）含量和脂质过氧化水平（TBARS）进行了比较测定。在非胁迫条件下，黄顶菊属物种中仅CAT（降低）、APX和GR（均升高）与从C₃到C₄的羧化途径类型之间存在相关性。然而，它们在抗氧化防御方面对PEG诱导的渗透胁迫反应不同。在C₃的粗壮黄顶菊中观察到H₂O₂和TBARS含量增加最多，而在类C₄的布朗氏黄顶菊和C₄的二齿黄顶菊中检测到的增加最少，这表明类C₄和C₄物种能更有效地应对氧化胁迫。这是通过二齿黄顶菊中更好的诱导酶促防御（SOD、CAT、POX和APX活性增加）和布朗氏黄顶菊中的非酶抗氧化剂实现的。作为对PEG诱导的氧化胁迫的反应，在所有黄顶菊属物种中都观察到了同工酶活性和同工酶模式的变化，这可能与细胞不同区室中产生的ROS有关。
