Perry K L, Palukaitis P
Department of Plant Pathology, Cornell University, Ithaca, NY 14853-5908.
Mol Gen Genet. 1990 Mar;221(1):103-12. doi: 10.1007/BF00280374.
The organization of the intergenic spacer of a 9.04 kb tomato ribosomal RNA gene (rDNA) was determined. The 3258 bp spacer contains two major repeat elements enclosing a region which includes 351 bp of an 81.8% A --T rich sequence. A block of nine 53 bp repeats begins 388 bp downstream from the 3' end of the 25S rRNA. The A--T rich domain is followed by a block of six 141 bp repeats terminating 818 bp upstream from the 5' end of the 18S rRNA. Major pre-rRNAs of 7.6 and 6.5 kb were observed by Northern hybridization analysis. The 5' termini of these RNAs were identified through combined S1 nuclease and primer extension analyses. The 7.6 kb RNA is likely to be the primary transcript; its 5' terminus lies within a sequence motif. TATA(R)TA(N)GGG, conserved at the termini of transcripts mapped in three other plant species. The 6.5 kb RNA is interpreted as a 5' end processed transcript derived from the 7.6 kb RNA. Comparative analysis of transcribed sequences revealed a 25 bp domain of the intergenic spacer which is relatively conserved among five plant species. The conservation of spacer sequences in plants is in contrast to the extensive sequence divergence of the intergenic spacer in other non-plant systems and suggests a conserved function directed by these sequences.
确定了一个9.04 kb番茄核糖体RNA基因（rDNA）基因间隔区的组织方式。3258 bp的间隔区包含两个主要重复元件，包围着一个区域，该区域包括一段351 bp的富含A - T（81.8%）的序列。一组九个53 bp的重复序列从25S rRNA 3'端下游388 bp处开始。富含A - T的结构域之后是一组六个141 bp的重复序列，终止于18S rRNA 5'端上游818 bp处。通过Northern杂交分析观察到了7.6 kb和6.5 kb的主要前体rRNA。通过S1核酸酶和引物延伸分析相结合的方法确定了这些RNA的5'末端。7.6 kb的RNA可能是初级转录本；其5'末端位于一个序列基序TATA(R)TA(N)GGG内，该基序在其他三种植物物种中绘制的转录本末端是保守的。6.5 kb的RNA被解释为源自7.6 kb RNA的5'末端加工转录本。对转录序列的比较分析揭示了基因间隔区的一个25 bp结构域，该结构域在五种植物物种中相对保守。植物中间隔区序列的保守性与其他非植物系统中基因间隔区广泛的序列差异形成对比，表明这些序列具有保守功能。
