Expression of nuclear genes for chloroplast ribosomal proteins.

我在水稻核基因组中发现了两个编码叶绿体核糖体蛋白L12的基因。这些基因分别命名为rpl12-1和rpl12-2(rpl12，核糖体蛋白L12)。用特定探针进行的Northern分析表明，这两个基因都是转录的。每个基因的表达似乎都有不同的调控机制。也有人认为rpl12-1的表达是以器官特异性的方式控制的。在单子叶植物和双子叶植物中，成熟肽部分推导的氨基酸序列比转运肽部分更加保守。利用已报道的植物rpl12S转运肽区的核苷酸序列构建了系统发育树。该树包括对获得转运肽的时间和基因在进化过程中被复制的时间的估计。根据我们的假设，核转位的叶绿体核糖体蛋白L12基因在单子叶和双子叶分化后获得转运肽，然后在单子叶和双子叶中独立复制，然后水稻和黑麦分枝部分。我克隆了一个新的水稻和拟南芥核糖体蛋白核基因，它类似于细菌核糖体蛋白S9(RPS9)。为了确定基因产物的亚细胞定位，我们将N-末端区域与绿色荧光蛋白(GFP)融合，并在水稻幼苗中瞬时表达。仅在叶绿体中检测到定位的荧光，表明该核基因编码叶绿体核糖体蛋白S9。水稻RPS9的N末端序列与水稻叶绿体核糖体蛋白L12的转运肽序列具有很高的相似性，表明这两种转运肽具有共同的谱系。

I identified two genes coding for chloroplast ribosomal protein L12 encoded in the nuclear genome of rice (Oryza sativa). The genes were designated rpl12-1 and rpl12-2 (rpl12, ribosomal protein L12). Northern analysis with specific probes revealed that both genes are transcribed. The expression of each gene seems to have different regulation machinery. It is also suggested that the expression of rpl12-1 is controlled in an organ-specific manner. The deduced amino acid sequences of the mature peptide parts are more conserved than those of the transit peptide parts in both monocotyledonous and dicotyledonous plants. A phylogenetic tree was constructed using the nucleotide sequences of the transit peptide region of reported plant rpl12s. The tree includes estimates of when the transit peptides were acquired and when the genes were duplicated in the course of evolution. According to our hypothesis, the nuclear-translocated chloroplast ribosomal protein L12 gene obtained its transit peptide after the divergence of monocots and dicots, then gene duplications occurred independently in monocots and dicots, and then rice and rye branched apart.I have cloned a novel nuclear gene for a ribosomal protein of rice and Arabidopsis that is like the bacterial ribosomal protein S9 (RPS9). To determine the subcellular localization of the gene product, we fused the N-terminal region and green fluorescent protein (GFP), and expressed it transiently in rice seedlings. Localized fluorescence was detectable only in chloroplasts, indicating this nuclear gene encodes chloroplast ribosomal protein S9. The N-terminal region of rice RPS9 was found to have a high sequence similarity to the transit peptide region of the rice chloroplast ribosomal protein L12, suggesting that these transit peptides have a common lineage.