Dickey L F, Petracek M E, Nguyen T T, Hansen E R, Thompson W F
Department of Botany, North Carolina State University, Raleigh, North Carolina 27695-7612, USA.
Plant Cell. 1998 Mar;10(3):475-84. doi: 10.1105/tpc.10.3.475.
Light regulation of Fed-1 mRNA abundance in the leaves of green plants is primarily a post-transcriptional process. Previously, we have shown that the Fed-1 mRNA light response requires an open reading frame, indicating that the light regulation of the mRNA depends on its concurrent translation. We now show that light-induced increases in Fed-1 mRNA abundance are associated with increases in polyribosome association that require both a functional AUG and a normal Fed-1 translational start context. We also present evidence that light regulation of Fed-1 mRNA levels requires more than efficient translation per se. Substitution of the efficiently translated tobacco mosaic virus Omega 5' untranslated region resulted in a loss of Fed-1 light regulation. In addition, we identified a CAT T repeat element located near the 5' terminus of the Fed-1 5' untranslated region that is essential for light regulation. We introduced two different mutations in the CAT T repeat element, but only one of these substitutions blocked the normal light effect on polyribosome association, whereas both altered dark-induced Fed-1 mRNA disappearance. The element may thus be important for Fed-1 mRNA stability rather than polyribosome loading. We propose a model in which Fed-1 mRNA is relatively stable when it is associated with polyribosomes in illuminated plants but in darkness is not polyribosome associated and is thus rapidly degraded by a process involving the CAT T repeat element.
绿色植物叶片中Fed-1 mRNA丰度的光调节主要是一个转录后过程。此前，我们已经表明Fed-1 mRNA的光反应需要一个开放阅读框，这表明mRNA的光调节取决于其同时进行的翻译。我们现在表明，光诱导的Fed-1 mRNA丰度增加与多核糖体结合的增加有关，这需要一个功能性的AUG和正常的Fed-1翻译起始上下文。我们还提供证据表明，Fed-1 mRNA水平的光调节需要的不仅仅是高效翻译本身。用高效翻译的烟草花叶病毒Omega 5'非翻译区进行替换导致Fed-1光调节丧失。此外，我们在Fed-1 5'非翻译区的5'末端附近鉴定出一个CAT T重复元件，它对光调节至关重要。我们在CAT T重复元件中引入了两种不同的突变，但只有其中一种替换阻断了光对多核糖体结合的正常影响，而两种突变都改变了黑暗诱导的Fed-1 mRNA消失。因此，该元件可能对Fed-1 mRNA稳定性而非多核糖体负载很重要。我们提出了一个模型，其中Fed-1 mRNA在光照植物中与多核糖体结合时相对稳定，但在黑暗中不与多核糖体结合，因此通过涉及CAT T重复元件的过程迅速降解。
