Submitted to: Molecular and Cellular Probes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2008
Publication Date: 10/7/2008
Citation: Deng,, X., Chen, J., Li,, H. 2008. Sequestering and characterization of sequence of a ribosomal RNA operon (rrn) from “Candiatus Liberibacter asiaticus”. Molecular and Cellular Probes. 22:338-340. Interpretive Summary: Citrus Huanglongbing (HLB) or yellow shoot disease is one of the most devastating diseases in citrus production worldwide. HLB now occurs in Florida, threatening the U.S. citrus industry. “Candidatus Liberibacter asiaticus” is a bacterium currently believed to be associated with HLB. Because this HLB associated bacterium is not culturable in artificial medium, research on genetic and biological traits of the bacterium is challenging. In this study, we enriched the HLB associated bacterium by culturing it in periwinkle plant. PCR primers were designed based on currently available sequence information. We obtained a segment of DNA encoding several genes of the HLB associated bacterium. Analyses of these genes revealed that the HLB bacterium was related to rhizobacteria. DNA regions unique to the HLB associated bacterium were identified. PCR primers from these unique regions were designed. Experimental results showed that these primers were specific to and efficient for detection of the HLB bacterium.
Technical Abstract: Citrus Huanglongbing (HLB, yellow shoot disease) is a highly destructive disease in citrus production worldwide. The disease is associated with the infection of “Candidatus Liberibacter asiaticus”. Analyses of rrn operon sequence are important in “Ca. L. asiaticus” characterization. Thus far, only sequences of the 16S rRNA gene and 16S-23S rRNA intergenic transcribed spacer (ITS) have been reported. In this study, a 5,005 bp rrn DNA sequence of “Ca. L. asiaticus” was obtained by PCR using primers conserved to Rhizobiaceae in the alpha-proteobacteria. The rrn locus consisted of a 16S rRNA gene (rrs), an ITS containing two genes of tRNAIle and tRNAAla, a 23S rRNA gene (rrl), an ITS without a tRNA gene, and a 5S rRNA gene (rrf). As in previous reports on rrs sequence, rrl and rrf were also related (89-90%) to those of the Rhizobiaceae. Interestingly, the tRNAIle and tRNAAla genes were more related to those of non-Rhizobiaceae alpha-proteobacteria. The non-tRNA gene regions of the 16S-23S rRNA ITS and the 23S-5S rRNA ITS did not share significant similarity to any currently known bacterial DNA sequences. Sequences from these unique regions were highly specific to “Ca. L. asiaticus” and useful for detection of the bacterium.