Comparative metagenome sequencing of ‘Candidatus Liberibacter solanacerum’ haplotypes A and B reveals hypervariable phage-like regions
C. JOHNSON (1), S. Thompson (2), A. Wen (1), Y. P. Duan (3), G. Smith (2), N. C. Gudmestad (1). (1) North Dakota State University, Fargo, ND, U.S.A.; (2) New Zealand Plant and Food Research, Lincoln, New Zealand; (3) U.S. Horticultural Research Laboratory, Fort Pierce, FL, U.S.A.
It has been demonstrated that Zebra Chip disease of potato is caused by two distinct haplotypes (A and B) of ‘<i>Candidatus</i> Liberibacter solanacearum’ (Lso). Lso is an unculturable phloem restricted <i>a</i>-proteobacteria transmitted from plant to plant through the feeding activity of the potato/tomato psyllid (<i>Bactericera cockerelli</i>). In order to better understand the biology and genetic variability of Lso, metagenomic sequencing was performed on Lso-positive psyllids. Field collected insects were used to start colonies on eggplant and potato in greenhouse cages. QPCR was used to monitor the percentage Lso+ psyllids, the relative Lso titer of infected psyllids, and Lso haplotype of each colony. High titer Lso DNA extracted from psyllids was subjected to IonTorrent sequencing using the IonTorrent 318 chip. The previously sequenced LsoB genome was used in template based genome assemblies of the IonTorrent reads. A reference LsoA genome was developed and expanded from sequences identified by homology to LsoB. Comparisons were made between the LsoA and LsoB genomes resulting in identification of distinct hypervariable regions of DNA. BLAST analysis of these regions reveals homology to bacteriophage sequences.
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