Site-recognition of RNA editing in chloroplasts

1. RNA编辑位点(1)在烟草叶绿体ndhD mRNA中发现了两个额外的位点。因此，位点总数为38个，是迄今为止在高等植物叶绿体中发现的最多的位点。(2)重新研究了烟草祖先（N sylvestris和N. tomentosiformis）的ndhD mrna中ACG对AUG RNA的编辑，后者的这种编辑取决于培养条件。2 .体外RNA编辑检测方法的改进：建立了一种快速、简便的荧光双脱氧核苷酸体外检测方法。利用上述方法，测定了5种烟草ndh mRNA中19个位点的编辑活性。ndhB mRNA的顺式元件被定义为从6到10的5个核苷酸（nt），而ndhF mRNA有两个独立的顺式元件，从1到15的15个核苷酸和从36到40.4的5个核苷酸。利用荧光mrna，我们尝试了一种检测反式因子进行编辑的方法。位点识别因子分析分离出56 kD的psbE mRNA编辑反式因子，并确定其部分氨基酸序列。在数据库中没有发现类似的序列。

1. RNA editing sites(1) Two additional sites were identified in the ndhD mRNA from tobacco (N. tabacum) chloroplasts. The total number of sites is thus 38, the most so far found in higher plant chloroplasts.(2) ACG to AUG RNA editing in ndhD mRNAs from tobacco progenitors (N sylvestris and N. tomentosiformis) was reexamined, and this editing in the latter species occurred depending on culture conditions.2. Improvement of the in vitro RNA editing assayA rapid and simple in vitro assay was established using fluorescent dideoxynucleotides.3. Cis-elements for RNA editingUsing the above assay, editing activities of 19 sites in five tobacco ndh mRNA species were measured. A cis-element in the ndhB mRNA was defined to be 5 nucleotides (nt) from-6 to-10, whereas ndhF mRNAs have two separate cis-elements, 15 nt from-1 to-15 and 5 nt from-36 to-40.4. Trans-factorsUsing fuorescent mRNAs, a method to detect trans-factors for editing was tried.5. Analysis of site-recognition factorsThe 56 kD trans-factor for psbE mRNA editing was isolated, and its partial amino acid sequences were determined. No similar sequence was found in databases.