Pandey Akshay, Suman Shubhankar, Chandna Sudhir
Natural Radiation Response Mechanisms Group, Division of Radiation Biosciences, Institute of Nuclear Medicine and Allied Sciences, Brig. S.K. Mazumdar Road, Delhi -110054, India.
Bioinformation. 2010 Jun 24;5(1):21-7. doi: 10.6026/97320630005021.
Certain insects (e.g., moths and butterflies; order Lepidoptera) and nematodes are considered as excellent experimental models to study the cellular stress signaling mechanisms since these organisms are far more stress-resistant as compared to mammalian system. Multiple factors have been implicated in this unusual response, including the oxidative stress response mechanisms. Radiation or chemical-induced mitochondrial oxidative stress occurs through damage caused to the components of electron transport chain (ETC) leading to leakage of electrons and generation of superoxide radicals. This may be countered through quick replacement of damaged mitochondrial proteins by upregulated expression. Since the ETC comprises of various proteins coded by mitochondrial DNA, variation in the composition, expressivity and regulation of mitochondrial genome could greatly influence mitochondrial role under oxidative stress conditions. Therefore, we carried out in silico analysis of mitochondrial DNA in these organisms and compared it with that of the stress-sensitive humans/mammals. Parameters such as mitochondrial genome organization, codon bias, gene expressivity and GC(3) content were studied. Gene arrangement and Shine-Dalgarno (SD) sequence patterns indicating translational regulation were distinct in insect and nematodes as compared to humans. A higher codon bias (ENC≫35) and lower GC(3) content (≫0.20) were observed in mitochondrial genes of insect and nematodes as compared to humans (ENC>42; GC3>0.20), coupled with low codon adaptation index among insects. These features indeed favour higher expressivity of mitochondrial proteins and might help maintain the mitochondrial physiology under stress conditions. Therefore, our study indicates that mitochondrial genome organization may influence stress-resistance of insects and nematodes.
某些昆虫（如蛾类和蝴蝶；鳞翅目）和线虫被认为是研究细胞应激信号传导机制的优秀实验模型，因为与哺乳动物系统相比，这些生物体具有更强的抗应激能力。多种因素与这种异常反应有关，包括氧化应激反应机制。辐射或化学诱导的线粒体氧化应激是通过对电子传递链（ETC）成分造成损伤而发生的，导致电子泄漏和超氧自由基的产生。这可以通过上调表达快速替换受损的线粒体蛋白来对抗。由于ETC由线粒体DNA编码的各种蛋白质组成，线粒体基因组的组成、表达能力和调控的变化可能会极大地影响氧化应激条件下线粒体的作用。因此，我们对这些生物体的线粒体DNA进行了计算机分析，并将其与应激敏感的人类/哺乳动物的线粒体DNA进行了比较。研究了线粒体基因组组织、密码子偏好、基因表达能力和GC(3)含量等参数。与人类相比，昆虫和线虫中指示翻译调控 的基因排列和Shine-Dalgarno（SD）序列模式明显不同。与人类（ENC>42；GC3>0.20）相比，在昆虫和线虫的线粒体基因中观察到更高的密码子偏好（ENC≫35）和更低的GC(3)含量（≫0.20），同时昆虫中的密码子适应指数较低。这些特征确实有利于线粒体蛋白的更高表达，并可能有助于在应激条件下维持线粒体生理功能。因此，我们的研究表明线粒体基因组组织可能影响昆虫和线虫的抗应激能力。
