title: Promiscuous Pathogenicity Islands and Phylogeny of Pathogenic Streptomyces spp.
abstract: Approximately 10 Streptomyces species cause disease on underground plant structures. The most economically important of these is potato scab, and the most studied of these pathogens is Streptomyces scabiei (syn. S. scabies). The main pathogenicity determinant of scab-causing Streptomyces species is a nitrated diketopiperazine, known as thaxtomin A (ThxA). In the pathogenic species Streptomyces turgidiscabies, ThxA biosynthetic genes reside on a mobile pathogenicity island (PAI). However, the mobilization of PAIs in other Streptomyces species remains uncharacterized. Here, we investigated the mobilization of the PAI of S. scabiei 87-22. Based on whole genome sequences, we inferred the evolutionary relationships of pathogenic Streptomyces species and discovered that Streptomyces sp. strain 96-12, a novel pathogenic species isolated from potatoes in Egypt, was phylogenetically grouped with nonpathogenic species rather than with known pathogenic species. We also found that Streptomyces sp. strain 96-12 contains a PAI that is almost identical to the PAI in S. scabiei 87-22, despite significant differences in their genome sequences. This suggested direct or indirect in vivo mobilization of the PAI between S. scabiei and nonpathogenic Streptomyces species. To test whether the S. scabiei 87-22 PAI could, indeed, be mobilized, S. scabiei 87-22 deletion mutants containing antibiotic resistance markers in the PAI were mated with Streptomyces diastatochromogenes, a nonpathogenic species. The PAI of S. scabiei was site-specifically inserted into the aviX1 gene of S. diastatochromogenes and conferred pathogenicity in radish seedling assays. Our results demonstrated that S. scabiei, the earliest described Streptomyces pathogen, could be the source of a PAI responsible for the emergence of novel pathogenic species.
authors: 1 Department of Plant Pathology, University of Florida, Gainesville, Florida, U.S.A.;
authors: Yucheng
authors: Y
authors: Zhang
authors: 2 Department of Biology, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada;
authors: Dawn R D
authors: DR
authors: Bignell
authors: 3 Department of Medicinal Chemistry, University of Florida, Gainesville, Florida, U.S.A.; and.
authors: Ran
authors: R
authors: Zuo
authors: 4 College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China.
authors: Qiurong
authors: Q
authors: Fan
authors: 1 Department of Plant Pathology, University of Florida, Gainesville, Florida, U.S.A.;
authors: Jose C
authors: JC
authors: Huguet-Tapia
authors: 3 Department of Medicinal Chemistry, University of Florida, Gainesville, Florida, U.S.A.; and.
authors: Yousong
authors: Y
authors: Ding
authors: 1 Department of Plant Pathology, University of Florida, Gainesville, Florida, U.S.A.;
authors: Rosemary
authors: R
authors: Loria
mesh_terms: D005075:Biological Evolution; D044404:Genomic Islands / Q000235:genetics*; D007211:Indoles / Q000378:metabolism*; D010802:Phylogeny; D010879:Piperazines / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology*; D011198:Solanum tuberosum / Q000382:microbiology*; D013302:Streptomyces / Q000235:genetics / Q000472:pathogenicity*; D014774:Virulence
chemical_list: D007211:Indoles; D010879:Piperazines; C406691:thaxtomine A