Aims Metacaspases are cysteine-dependent proteases, which play essential roles in programmed cell death (PCD), and caspase-3-like protease is the crucial executioner. However, its response mechanism to aluminum (Al)-induced PCD is still elusive. Methods Here, the type I metacaspase gene in peanut ( Arachis hypoganea L.), AhMC1 , was cloned from the Al-sensitive cultivar ZH2. Physiological and biochemical methods, as well as gene expression analyses, were employed to explore its function in Al-induced PCD in peanut root tips. Results AhMC1 had a 1068-bp open reading frame, encoding a peptide of 355 amino acids, and the purified protein exhibited a high caspase-3-like protease activity. Its expression levels in different tissues of peanut varieties ZH2 and 99–1507 (Al-tolerant) varied under Al-stress conditions. The subcellular localization indicated that AhMC1 was transferred from mitochondria into the cytoplasm. Furthermore, overexpressing AhMC1 reduced the resistance to Al stress. Sense transgenic plants showed a low relative root growth rate, and reduced superoxide dismutase, peroxidase, and catalase activities, compared with wild-type and antisense transgenic plants under Al-stress conditions, but had a high root-cell death rate, and increased Al and maleic dialdehyde contents. Conclusions The data suggest that metacaspase AhMC1 is a positive factor in Al-induced PCD in peanut root tips.

中文翻译：

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Metacaspase MC1 增强铝诱导的花生根尖细胞程序性细胞死亡

目的 Metacaspases 是半胱氨酸依赖性蛋白酶，在程序性细胞死亡 (PCD) 中发挥重要作用，而 caspase-3 样蛋白酶是关键的执行者。然而，其对铝 (Al) 诱导的 PCD 的响应机制仍然难以捉摸。方法这里，从对铝敏感的品种ZH2克隆了花生(Arachis hypoganea L.)中的I型metacaspase基因AhMC1。生理生化方法以及基因表达分析被用来探索其在铝诱导花生根尖 PCD 中的作用。结果AhMC1具有1068bp的开放阅读框，编码355个氨基酸的肽段，纯化后的蛋白表现出较高的caspase-3样蛋白酶活性。其在花生品种ZH2和99-1507（耐铝）不同组织中的表达水平在铝胁迫条件下发生变化。亚细胞定位表明AhMC1从线粒体转移到细胞质中。此外，过表达 AhMC1 会降低对铝应力的抵抗力。与野生型和反义转基因植物相比，有义转基因植物在铝胁迫条件下表现出较低的相对根生长率，降低了超氧化物歧化酶、过氧化物酶和过氧化氢酶的活性，但根细胞死亡率较高，铝含量增加和马来二醛含量。结论 数据表明，metacaspase AhMC1 是铝诱导花生根尖 PCD 的积极因素。和过氧化氢酶活性，与 Al 胁迫条件下的野生型和反义转基因植物相比，但具有较高的根细胞死亡率，并增加了 Al 和马来酸二醛的含量。结论 数据表明，metacaspase AhMC1 是铝诱导花生根尖 PCD 的积极因素。和过氧化氢酶活性，与 Al 胁迫条件下的野生型和反义转基因植物相比，但具有较高的根细胞死亡率，并增加了 Al 和马来酸二醛的含量。结论 数据表明，metacaspase AhMC1 是铝诱导花生根尖 PCD 的积极因素。