Catalase (CAT) dismutates the reactive oxygen species H2O2 into water and dioxygen and in plants; it is located in peroxisomes and glyoxysomes. In the present study, we investigated the effect of cadmium (a well-known oxidative stress inducer) on catalase in roots and cotyledons of developing sunflower seedlings, at 10 microM and 100 microM. Although germination was unaltered after 48 h of exposure to 100 microM Cd2+, root length was significantly reduced. CAT activity was also significantly reduced, but this activity was completely restored (10 microM treatment) or even enhanced (100 microM treatment) 24 h later. Although CAT protein abundance remained similar to control in roots and cotyledons of Cd-treated seedlings, cadmium produced CAT protein oxidation, indicating that the mechanism of CAT inactivation by Cd2+ involves oxidation of the protein structure. The transcripts of the four genes described for sunflower (CATA1 to CATA4) increased after cadmium treatment; CATA1 and CATA2 were the most overexpressed in cotyledon and root, respectively. The differential expression of catalase genes in sunflower seedlings under Cd stress might be related to the synthesis of CAT isoforms less sensitive to oxidation, which would prevent enzyme inactivation and H2O2 accumulation.

中文翻译：

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镉胁迫下发育中的向日葵幼苗中过氧化氢酶活性和表达的修饰。

过氧化氢酶（CAT）将活性氧H2O2分解为水和双氧以及植物。它位于过氧化物酶体和乙醛酸体中。在本研究中，我们研究了镉（一种众所周知的氧化应激诱导剂）对发育中的向日葵幼苗的根和子叶中过氧化氢酶的影响，其浓度为10 microM和100 microM。尽管暴露于100 microM Cd2 + 48小时后发芽没有改变，但根长却明显减少。CAT活性也显着降低，但24小时后该活性完全恢复（10 microM处理）甚至增强（100 microM处理）。尽管镉处理的幼苗的根和子叶中CAT蛋白的丰度仍然与对照相似，但镉产生了CAT蛋白氧化，表明Cd2 +使CAT失活的机制涉及蛋白质结构的氧化。镉处理后，描述的四个向日葵基因（CATA1至CATA4）的转录本增加了。CATA1和CATA2分别在子叶和根中表达最多。镉胁迫下向日葵幼苗中过氧化氢酶基因的差异表达可能与对氧化反应不敏感的CAT同工型的合成有关，这将阻止酶的失活和H2O2的积累。