Department of Biological Sciences and Technology, National University of Tainan, Tainan, Taiwan, ROC.
Aquat Toxicol. 2012 Nov 15;124-125:171-8. doi: 10.1016/j.aquatox.2012.08.014. Epub 2012 Aug 25.
The toxic effects of diethyl phthalate (DEP), a potent allelochemical, on the enzyme activity and polypeptide accumulation of glutamine synthetase (GS) in greater duckweed were investigated. In our previous studies, DEP induced oxidative responses at concentrations from 0.5 to 2 mM in greater duckweed and the antioxidant enzymes played important roles in the defense strategy against DEP stress. In this study, DAB-H(2)O(2) and NBT stain for superoxide radicals (O(2)(·-)), lipid peroxidation, HSP70, and ammonia accumulation in DEP-treated duckweed tissues revealed adverse effect of DEP in plant growth. Biochemical analysis and physiological methods were combined to investigate GS activity and polypeptide accumulation under DEP-induced stress. The results showed that GS activity was reduced with the increasing concentration of DEP, indicative of enhanced toxic effect. Immunoblot analysis with chloroplast soluble fractions indicated that the chloroplastic GS (GS2) polypeptide from greater duckweed was degraded under DEP stress conditions. The response of GS2 to the DEP stress may be modulated by means of redox change in plant tissues, chloroplasts, and chloroplast lysates. The results suggest that DEP is toxic to the greater duckweed by inhibition of the GS isoenzymes in nitrogen assimilation and the GS2 plays important roles in the adaptation strategy against DEP toxicity.
邻苯二甲酸二乙酯（DEP）是一种强效的化感物质，本研究探讨了其对满江红中谷氨酰胺合成酶（GS）的酶活性和多肽积累的毒性作用。在我们之前的研究中，DEP 在 0.5 至 2 mM 的浓度下诱导了满江红的氧化反应，抗氧化酶在抵御 DEP 胁迫的防御策略中发挥了重要作用。在这项研究中，DAB-H(2)O(2)和 NBT 染色用于超氧自由基（O(2)(·-))、脂质过氧化、HSP70 和氨积累的检测，结果表明 DEP 对植物生长有不良影响。本研究结合生物化学分析和生理方法，研究了 DEP 诱导胁迫下 GS 活性和多肽积累。结果表明，随着 DEP 浓度的增加，GS 活性降低，表明毒性作用增强。用叶绿体可溶性部分进行免疫印迹分析表明，DEP 胁迫条件下满江红的叶绿体 GS（GS2）多肽被降解。GS2 对 DEP 胁迫的反应可能是通过植物组织、叶绿体和叶绿体裂解物中的氧化还原变化来调节的。研究结果表明，DEP 通过抑制氮同化中的 GS 同工酶对满江红有毒，GS2 在应对 DEP 毒性的适应策略中发挥重要作用。
