Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2001
Publication Date: 2/1/2002
Citation: BUKHALID, R.A., TAKEUCHI, T., LABEDA, D.P., LORIA, R. HORIZONTAL TRANSFER OF THE PLANT VIRULENCE GENE, NEC1, AND FLANKING SEQUENCES AMONG GENETICALLY DISTINCT STRAINS IN THE DIASTATOCHROMOGENES CLUSTER. JOURNAL OF APPLIED & ENVIRONMENTAL MICROBIOLOGY. 2002. V. 68. P. 738-744. Interpretive Summary: Common scab is an important disease that affects potatoes and other root crops, such as carrot, radish, beet, and turnip. The soil bacterium, Streptomyces scabies, has been long recognized as the primary cause of this disease, although recently other species of Streptomyces have also been found to cause the disease. A study of the genes related to scab production in a range of disease-causing Streptomyces from various different plants and geographic locations showed that this genetic information has been transferred between these species. This information is extremely valuable for individuals involved in quarantine of imported plant material or plant breeding for disease resistance.
Technical Abstract: Evidence for the horizontal transfer of a pathogenicity island (PAI) carrying the virulence gene nec1 and flanking sequences among Streptomyces strains in the 'Diastatochromogenes' cluster is presented. Plant pathogenic, thaxtomin-producing, Streptomyces strains, previously classified as S. scabies based on the conventionally used phenotypic characteristics, were found to be genetically distinct from S. scabies based on DNA relatedness and 16S rDNA sequence analysis. Pairwise DNA-DNA hybridizations between some of these strains and the S. scabies type strain were as low as 36%, a value much below what is conventionally accepted for species identity (70%). The sequence of the nec1 gene, however, was identical in all the S. scabies-like strains tested, irrespective of their DNA relatedness to the type strain of S. scabies, their geographic origin, or isolation host. Furthermore, a 26 kb DNA fragment including and flanking nec1was also conserved among these strains based on restriction and Southern analyses.