Copper induces an oxidative stress condition in the marine alga Ulva compressa that is due to the production of superoxide anions and hydrogen peroxide, mainly in organelles. The increase in hydrogen peroxide is accompanied by increases in intracellular calcium and nitric oxide, and there is a crosstalk among these signals. The increase in intracellular calcium activates signaling pathways involving Calmodulin-dependent Protein Kinases (CaMKs) and Calcium-Dependent Protein Kinases (CDPKs), leading to activation of gene expression of antioxidant enzymes and enzymes involved in ascorbate (ASC) and glutathione (GSH) synthesis. It was recently shown that copper also activates Mitogen-Activated Protein Kinases (MAPKs) that participate in the increase in the expression of antioxidant enzymes. The increase in gene expression leads to enhanced activities of antioxidant enzymes and to enhanced levels of ASC and GSH. In addition, copper induces an increase in photosynthesis leading to an increase in the leve of Nicotinamide Adenine Dinucleotide Phosphate (NADPH). Copper also induces an increase in activities of enzymes involved in C, N, and S assimilation, allowing the replacement of proteins damaged by oxidative stress. The accumulation of copper in acute exposure involved increases in GSH, phytochelatins (PCs), and metallothioneins (MTs) whereas the accumulation of copper in chronic exposure involved only MTs. Acute and chronic copper exposure induced the accumulation of copper-containing particles in chloroplasts. On the other hand, copper is extruded from the alga with an equimolar amount of GSH. Thus, the increases in activities of antioxidant enzymes, in ASC, GSH, and NADPH levels, and in C, N, and S assimilation, the accumulation of copper-containing particles in chloroplasts, and the extrusion of copper ions from the alga constitute essential mechanisms that participate in the buffering of copper-induced oxidative stress in U. compressa.

中文翻译：

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海洋Macroalga Ulva compressa（Chlorophyta）的铜耐受性，积累和解毒机制：20年的研究。

铜在海藻Ulva compressa中诱导氧化应激条件这是由于主要在细胞器中产生了超氧阴离子和过氧化氢。过氧化氢的增加伴随着细胞内钙和一氧化氮的增加，并且在这些信号之间存在串扰。细胞内钙的增加激活了钙调蛋白依赖性蛋白激酶（CaMKs）和钙依赖性蛋白激酶（CDPKs）的信号传导途径，导致抗氧化剂酶和抗坏血酸（ASC）和谷胱甘肽（GSH）合成涉及的酶的基因表达被激活。 。最近显示，铜还激活了参与抗氧化酶表达增加的丝裂原活化蛋白激酶（MAPK）。基因表达的增加导致抗氧化剂酶的活性增强以及ASC和GSH水平升高。此外，铜诱导光合作用增加，导致烟酰胺腺嘌呤二核苷酸磷酸盐（NADPH）的水平增加。铜还诱导参与C，N和S同化的酶的活性增加，从而可以替代因氧化应激而受损的蛋白质。急性暴露中的铜积累涉及GSH，植物螯合素（PCs）和金属硫蛋白（MT）的增加，而慢性暴露中的铜积累仅涉及MT。急性和慢性铜暴露引起叶绿体中含铜颗粒的积累。另一方面，铜以等摩尔量的GSH从藻类中挤出。因此，抗氧化酶的活性，ASC，GSH和NADPH水平以及C，N和S同化的增加，U.compressa。