Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2008
Publication Date: 6/1/2008
Citation: Stenger, D.C., Chen, J. 2008. Xylella fastidiosa isolates from mulberry harbor a 25 kilobase pair plasmid with extensive sequence identity to a plasmid from Verminephrobacter eiseniae. Phytopathology 98:S150.
Technical Abstract: A 25 kbp plasmid was present in each of four Californian isolates of Xylella fastidiosa from mulberry affected with leaf scorch disease. Fragments of each plasmid were cloned into E. coli, sequenced, and assembled into circular contigs of 25,105 bp (pXF-RIV11 and pXF-RIV16) or 24,372 bp (pXF-RIV19 and pXF-RIV25). The four sequences shared greater than 99.8% sequence identity, excluding a 733 bp insertion in pXF-RIV11 and pXF-RIV16. BLAST searches indicated that eight regions (totaling 19,252 bp) shared 75% to 83% nucleotide sequence identity with pVEIS01, a 31 kbp plasmid from the earthworm symbiont Verminephrobacter eiseniae. Sequences related to pVEIS01 appear to encode a Type IV secretion system and other genes with DNA transfer function. Regions of the 25 kbp plasmids lacking similarity to pVEIS01 encoded repB/MobA-like and replication initiator genes previously identified on pXF5823 of X. fastidiosa. The 733 bp insertion of the two larger plasmids encoded a conjugal transfer protein nearly identical to that encoded by the chromosome of X. fastidiosa Temecula 1. These results indicate that mulberry isolates of X. fastidiosa harbor plasmids encoding genes associated with DNA transfer and that at some time in the past, ancestors of two unrelated bacterial species occupying distinctly different niches appear to have exchanged genetic material.