Gene Organization of a Ribosomal RNA Operon in Phytoplasma Associated with the Loofah Witches' Broom

• Main Authors: Chi-chang Tsai, 蔡祁樟
• Other Authors: Kuo-chieh Ho
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/01696787324402650827

碩士 === 國立臺灣大學 === 植物學研究所 === 87 === Previously, using insert DNA fragment of clone 138, which contained Mycoplasma genitalium rRNA gene, as probe to screen a Hind III genonic library of loofah witches' broom (LfWB) phytoplasma, a clone (cloneH1) with a 4.0-kb insert was obtained in our lab. Comparing the nucleotide sequence of this 4.0-kb fragment with the nucleotide sequence of M. genitalium genomic databank revealed that it contained entire 16S and two-third 23S rRNA sequence of LfWB phytoplasma, with a tRNAIle gene in the spacer region between 16S and 23S rRNA genes. In order to clone the complete LfWB phytoplasma rRNA operon, an 1.0-kb EcoR I-Hind III fragment of the 4.0-kb insert was used as probe to screen a EcoR I genomic library of LfWB phytoplasma. A clone (clone D1) with a 6.0-kb insret was obtained. Aligment of this 6.0-kb sequence with M. genitulium genomic databank had shown it contained the other one-third 23S rRNA gene and entire 5S rRNA gene, and two tRNA genes (tRNAVal and tRNAAsn ) downstream from few bases of 5S rRNA gene. The nucleotide sequence of these two fragments (4.0-kb, 6.0-kb) were compared with the rRNA operon sequence of Mollicutes and other gram-positive bacteria. The results indicated these two fragments contained the complete sequence of the LfWB phytoplasma rRNA operon with a context of 5'-16S-23S-5S-3', presenting a typical rRNA operon orginization of prokaryotes. This was the first rRNA operon of a phytoplasma published. The secondary structure of the genes in the operon were also analyzed.