Submitted to: Conference of International Organization of Citrus Virologists
Publication Type: Abstract Only
Publication Acceptance Date: 6/30/2013
Publication Date: 7/28/2013
Citation: Chen, J., Deng, X., Wang, X., Yokomi, R.K. 2013. Prophages in “Candidatus Liberibacter asiaticus” and Spiroplasma citri. In: Book of Abstracts, 19th Conference of International Organization of Citrus Virologists. p.78. Interpretive Summary:
Technical Abstract: A prophage is bacteriophage DNA integrated into a bacterial chromosome or existing as a plasmid inside the bacterial cell. It provides important biological traits of bacteria that may involve virulence, environmental adaptation, strain specification and genome evolution. Genome sequence analyses indicate that both "Candidatus Liberibacter asiaticus" and Spiroplasma citri harbor prophages. “Ca. L. asiaticus” is associated with citrus Huanglongbing (HLB, yellow shoot disease) and S. citri causes citrus stubborn disease (CSD). “Ca. L. asiaticus” is not culturable in vitro. S. citri is culturable but the process is highly challenging. For these reasons, knowledge of the biology of the two bacteria is very limited. To study the prophage diversity of “Ca. L. asiaticus” in China where HLB has been endemic for over 100 years, 12 consecutive open reading frames (ORFs) in a prophage of a Florida “Ca. L. asiaticus” isolate were selected and primers were synthesized. Using these primers with PCR, 150 “Ca. L. asiaticus” samples from southern China were examined. At least three prophage types were detected, indicating a possible rich pool of “Ca. L. asiaticus” prophage in southern China. Since S. citri was culturable, pure culture of nine S. citri strains were obtained and whole genome sequences were generated. Two prophage/phage genes were selected and their abundance in each of the 9 whole genome sequences was estimated. Copy number of one gene varied from 13 to 154. Copy number of the other gene varied from 11 to 56. These results suggest that in addition to the chromosomal form, prophages of S. citri may also exist in extrachromosomal forms. Overall, these studies demonstrate that prophages are important constituents of both “Ca. L. asiaticus” and S. citri. More information on prophages are needed for better understanding of the two fastidious prokaryotes important to world citrus industry.