The translation inactivation in the pseudogenization process of chloroplast genes

植物已经朝着减少叶绿体基因的方向进化。叶绿体基因的假原化过程尚不清楚。在许多高等植物中，叶绿体核糖体蛋白S16的基因rps16不仅由核基因组编码，也由叶绿体基因组编码。因此，叶绿体rps16基因的假基因化可能正在进行中。在本研究中，我们发现烟草叶绿体中的rps16基因转录良好，其转录本被正确剪接，但其mRNA没有被翻译。此外，我们还确定了烟草叶绿体中rps16mRNA翻译失活的顺式调控元件。根据这些结果，翻译失活可能是叶绿体基因组中成为假基因的触发因素之一。

Plants have evolved in the direction of decreasing chloroplast genes. It remains unclear the pseudogenization process of chloroplast genes. In many higher plants, the gene for chloroplast ribosomal protein S16, rps16, is encoded not only by the nuclear genome but also by the chloroplast genome. Thus, it is possible that the pseudogenization of chloroplast rps16 gene is in progress. In this study, we found that the rps16 gene in tobacco chloroplasts is well transcribed and its transcript is correctly spliced, but mRNA is not translated. Furthermore, we determined the cis-regulatory element for translation inactivation of rps16 mRNA in tobacco chloroplasts. From these results, the translation inactivation may be the one of the triggers to become the pseudogenes in the chloroplast genome.