MSU-DOE Plant Research Laboratory and Biochemistry Department, Michigan State University, 48824-1312, East Lansing, MI, USA.
Planta. 1989 Dec;180(1):82-9. doi: 10.1007/BF02411413.
Changes in the mitochondrial electrontransport chain were followed in the thermogenic inflorescence ofSauromatum guttatum Schott from 5d before thermogenesis to 3d thereafter. The capacities of the alternative and cytochrome pathways of mitochondrial electron transport were found to be developmentally coordinated to contribute to the thermogenic events in the appendix and the sterile floral regions. Electron flow through the alternative pathway, is believed primarily responsible for heat production, and this pathway was expressed to the highest degree in both tissues during thermogenesis. In the appendix, the cytochrome chain was shut down considerably during thermogenesis, forcing electron flow through the alternative pathway and thus yielding maximum heat production. The shut-down of the cytochrome chain does not occur in the sterile floral region which may explain why this region is not as thermogenic as the appendix. Cytochrome-oxidase difference spectra indicated that the cytochrome oxidase of appendix mitochondria was not capable of accepting electrons on the day of thermogenesis, and that this capacity was partially restored by the following day even though the tissue was senescing at this time point. Relative levels of messenger RNAs for cytochrome-oxidase subunits I and II were found to decrease the day before thermogenesis, which could result in lower levels of these proteins in appendix mitochondria on the day of thermogenesis.The capacity for overall mitochondrial protein synthesis was also investigated and was found to drop continuously from 5d before thermogenesis to 3d thereafter, even though the capacities of the electron-transport chain were changing dramatically. The levels of mitochondrial ribosomal RNA levels decreased during development, which could explain the overall drop in mitochondrial translational efficiency. Experiments concerning the synthesis of the alternative-oxidase proteins indicated that they were most likely nuclearly encoded, and that their expression could be induced by salicylic acid.
从生热前 5 天到生热后 3 天，我们对热体 Sauromatum guttatum Schott 的生热花序中线粒体电子传递链的变化进行了跟踪。发现线粒体电子传递的替代途径和细胞色素途径的能力在发育上是协调一致的，有助于生热事件在阑尾和不育花区的发生。电子通过替代途径的流动被认为主要负责产热，在生热过程中，这一途径在这两种组织中表达得最为强烈。在阑尾中，细胞色素链在生热过程中大大关闭，迫使电子通过替代途径流动，从而产生最大的产热量。细胞色素链的关闭不会发生在不育花区，这也许可以解释为什么这个区域不如阑尾那样生热。细胞色素氧化酶差示光谱表明，阑尾线粒体的细胞色素氧化酶在生热当天无法接受电子，而这种能力在第二天部分恢复，尽管此时组织正在衰老。细胞色素氧化酶亚基 I 和 II 的信使 RNA 相对水平在前一天生热前降低，这可能导致生热当天阑尾线粒体中这些蛋白质的水平降低。还研究了整体线粒体蛋白合成的能力，发现从生热前 5 天到生热后 3 天连续下降，尽管电子传递链的能力发生了巨大变化。线粒体核糖体 RNA 水平在发育过程中下降，这可以解释线粒体翻译效率的整体下降。关于替代氧化酶蛋白合成的实验表明，它们很可能是核编码的，并且它们的表达可以被水杨酸诱导。
