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Oral: 16th I.E., Melhus


Evolution of plant pathogenicity in Streptomyces
Y. ZHANG (1), D. Bignell (2), R. Zuo (3), Q. Fan (4), J. Huguet-Tapia (1), Y. Ding (3), R. Loria (1) (1) Department of Plant Pathology, University of Florida, U.S.A.; (2) Department of Biology, Memorial University of Newfoundland, Canada; (3) Department o

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Approximately ten Streptomyces species including the most widely distributed Streptomyces scabiei cause the potato scab disease. The main pathogenicity determinant of scab-causing Streptomyces species is the phytotoxin known as thaxtomin A (ThxA). In S. turgidiscabies, ThxA biosynthetic genes reside on a mobile pathogenicity island (PAI). However, the PAI mobilization in other Streptomyces species remains uncharacterized. We investigated the mobilization of the PAI of S. scabiei 87-22 both in vivo and in vitro. We sequenced genomes of ten pathogenic Streptomyces isolates from different locations, inferred the evolutionary relationships of pathogenic Streptomyces species, and identified a novel pathogenic species (S. sp. 96-12) that was isolated from Egypt. The PAI in S. sp. 96-12 is identical to the PAI in S. scabiei 87-22 despite differences in their whole genome sequences. This strongly suggested in vivo mobilization of this PAI in these two strains. To test whether the PAI in S. scabiei 87-22 could indeed be mobilized, S. scabiei 87-22 deletion mutants with antibiotic resistance markers in the PAI, were mated with S. diastatochromogenes, a nonpathogenic species. The PAI of S. scabiei was found to be site-specifically inserted into the aviX1 gene of S. diastatochromogenes and conferred pathogenicity. Our results demonstrated that the mobilization of the S. scabiei PAI could be responsible for the emergence of novel pathogenic species.