Functional coexpression of the mitochondrial alternative oxidase and uncoupling protein underlies thermoregulation in the thermogenic florets of skunk cabbage
Functional coexpression of the mitochondrial alternative oxidase and uncoupling protein underlies thermoregulation in the thermogenic florets of skunk cabbage
复制标题
DOI：
10.1104/pp.107.113563
复制
发表时间：
2008-02-01
期刊：
影响因子：
7.4
通讯作者：
Ito, Kikukatsu
中科院分区：
文献类型：
--
作者：
Onda, Yoshihiko;Kato, Yoshiaki;Ito, Kikukatsu
两种不同的线粒体能量耗散系统，替代氧化酶（AOX）和解偶联蛋白（UCP），分别被认为是植物和动物产热的关键组成部分。为了进一步阐明 AOX 和 UCP 在产热臭甘蓝 (Symplocarpus renifolius) 恒温产热过程中的生理作用，我们鉴定了产热细胞，并对这些基因在该生物体中进行了表达和功能分析。热成像分析与原位杂交相结合表明，假定的产热细胞围绕臭菘小花的雄蕊，并共表达 SrAOX 转录本，编码 Symplocarpus AOX 和 SrUCPb，编码缺乏第五个跨膜片段的新型 UCP。从产热小花中分离的线粒体表现出大量的亚油酸（LA）诱导的解偶联活性。此外，我们的结果表明，LA 能够抑制线粒体 AOX 途径，而丙酮酸刺激的 AOX 能力的比例并未受到 LA 的显着影响。有趣的是，即使环境空气温度从 10.3 摄氏度升高到 23.1 摄氏度或从 8.3 摄氏度升高到 24.9 摄氏度，SrAOX 和 SrUCPb 的蛋白表达水平也不受影响。因此，我们的结果表明，AOX 和 UCP 的功能性共表达是产热的分子基础，并且这些蛋白的翻译后修饰在产热过程中发挥着至关重要的作用。 在自然环境温度波动的条件下调节臭菘的恒温产热。
Two distinct mitochondrial energy dissipating systems, alternative oxidase (AOX) and uncoupling protein (UCP), have been implicated as crucial components of thermogenesis in plants and animals, respectively. To further clarify the physiological roles of AOX and UCP during homeothermic heat production in the thermogenic skunk cabbage (Symplocarpus renifolius), we identified the thermogenic cells and performed expression and functional analyses of these genes in this organism. Thermographic analysis combined with in situ hybridization revealed that the putative thermogenic cells surround the stamens in the florets of skunk cabbage and coexpress transcripts for SrAOX, encoding Symplocarpus AOX, and SrUCPb, encoding a novel UCP that lacks a fifth transmembrane segment. Mitochondria isolated from the thermogenic florets exhibited substantial linoleic acid (LA)-inducible uncoupling activities. Moreover, our results demonstrate that LA is capable of inhibiting the mitochondrial AOX pathway, whereas the proportion of pyruvate-stimulated AOX capacity was not significantly affected by LA. Intriguingly, the protein expression levels for SrAOX and SrUCPb were unaffected even when the ambient air temperatures increased from 10.3 degrees C to 23.1 degrees C or from 8.3 degrees C to 24.9 degrees C. Thus, our results suggest that functional coexpression of AOX and UCP underlies the molecular basis of heat production, and that posttranslational modifications of these proteins play a crucial role in regulating homeothermic heat production under conditions of natural ambient temperature fluctuations in skunk cabbage.