Browsing by Author "Staskawicz, Brian J."

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    Comparative genomics reveals diversity among xanthomonads infecting tomato and pepper
    Potnis, Neha; Krasileva, Ksenia V.; Chow, Virginia; Almeida, Nalvo F.; Patil, Prabhu B.; Ryan, Robert P.; Sharlach, Molly; Behlau, Franklin; Dow, J. Max; Momol, M. T.; White, Frank F.; Preston, James F.; Vinatzer, Boris A.; Koebnik, Ralf; Setubal, João C.; Norman, David J.; Staskawicz, Brian J.; Jones, Jeffrey B. (2011-03-11)
    Background Bacterial spot of tomato and pepper is caused by four Xanthomonas species and is a major plant disease in warm humid climates. The four species are distinct from each other based on physiological and molecular characteristics. The genome sequence of strain 85-10, a member of one of the species, Xanthomonas euvesicatoria (Xcv) has been previously reported. To determine the relationship of the four species at the genome level and to investigate the molecular basis of their virulence and differing host ranges, draft genomic sequences of members of the other three species were determined and compared to strain 85-10. Results We sequenced the genomes of X. vesicatoria (Xv) strain 1111 (ATCC 35937), X. perforans (Xp) strain 91-118 and X. gardneri (Xg) strain 101 (ATCC 19865). The genomes were compared with each other and with the previously sequenced Xcv strain 85-10. In addition, the molecular features were predicted that may be required for pathogenicity including the type III secretion apparatus, type III effectors, other secretion systems, quorum sensing systems, adhesins, extracellular polysaccharide, and lipopolysaccharide determinants. Several novel type III effectors from Xg strain 101 and Xv strain 1111 genomes were computationally identified and their translocation was validated using a reporter gene assay. A homolog to Ax21, the elicitor of XA21-mediated resistance in rice, and a functional Ax21 sulfation system were identified in Xcv. Genes encoding proteins with functions mediated by type II and type IV secretion systems have also been compared, including enzymes involved in cell wall deconstruction, as contributors to pathogenicity. Conclusions Comparative genomic analyses revealed considerable diversity among bacterial spot pathogens, providing new insights into differences and similarities that may explain the diverse nature of these strains. Genes specific to pepper pathogens, such as the O-antigen of the lipopolysaccharide cluster, and genes unique to individual strains, such as novel type III effectors and bacteriocin genes, have been identified providing new clues for our understanding of pathogen virulence, aggressiveness, and host preference. These analyses will aid in efforts towards breeding for broad and durable resistance in economically important tomato and pepper cultivars.
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    Computational and Biochemical Analysis of the Xanthomonas Effector AvrBs2 and Its Role in the Modulation of Xanthomonas Type Three Effector Delivery
    Zhao, Bingyu Y.; Dahlbeck, Douglas; Krasileva, Ksenia V.; Fong, Richard W.; Staskawicz, Brian J. (PLOS, 2011-12-01)
    Effectors of the bacterial type III secretion system provide invaluable molecular probes to elucidate the molecular mechanisms of plant immunity and pathogen virulence. In this report, we focus on the AvrBs2 effector protein from the bacterial pathogen Xanthomonas euvesicatoria (Xe), the causal agent of bacterial spot disease of tomato and pepper. Employing homology-based structural analysis, we generate a three-dimensional structural model for the AvrBs2 protein and identify catalytic sites in its putative glycerolphosphodiesterase domain (GDE). We demonstrate that the identified catalytic region of AvrBs2 was able to functionally replace the GDE catalytic site of the bacterial glycerophosphodiesterase BhGlpQ cloned from Borrelia hermsii and is required for AvrBs2 virulence. Mutations in the GDE catalytic domain did not disrupt the recognition of AvrBs2 by the cognate plant resistance gene Bs2. In addition, AvrBs2 activation of Bs2 suppressed subsequent delivery of other Xanthomonas type III effectors into the host plant cells. Investigation of the mechanism underlying this modulation of the type III secretion system may offer new strategies to generate broad-spectrum resistance to bacterial pathogens.
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    Novel insights into the genomic basis of citrus canker based on the genome sequences of two strains of Xanthomonas fuscans subsp aurantifolii
    Moreira, Leandro M.; Almeida, Nalvo F.; Potnis, Neha; Digiampietri, Luciano A.; Adi, Said S.; Bortolossi, Julio C.; da Silva, Ana C.; da Silva, Aline M.; de Moraes, Fabrício E.; de Oliveira, Julio C.; de Souza, Robson F.; Facincani, Agda P.; Ferraz, André L.; Ferro, Maria I.; Furlan, Luiz R.; Gimenez, Daniele F.; Jones, Jeffrey B.; Kitajima, Elliot W.; Laia, Marcelo L.; Leite, Rui P., Jr; Nishiyama, Milton Y.; Rodrigues Neto, Julio; Nociti, Letícia A.; Norman, David J.; Ostroski, Eric H.; Pereira, Haroldo A. Jr.; Staskawicz, Brian J.; Tezza, Renata I.; Ferro, Jesus A.; Vinatzer, Boris A.; Setubal, João C. (Biomed Central, 2010-04-13)
    Background Citrus canker is a disease that has severe economic impact on the citrus industry worldwide. There are three types of canker, called A, B, and C. The three types have different phenotypes and affect different citrus species. The causative agent for type A is Xanthomonas citri subsp. citri, whose genome sequence was made available in 2002. Xanthomonas fuscans subsp. aurantifolii strain B causes canker B and Xanthomonas fuscans subsp. aurantifolii strain C causes canker C. Results We have sequenced the genomes of strains B and C to draft status. We have compared their genomic content to X. citri subsp. citri and to other Xanthomonas genomes, with special emphasis on type III secreted effector repertoires. In addition to pthA, already known to be present in all three citrus canker strains, two additional effector genes, xopE3 and xopAI, are also present in all three strains and are both located on the same putative genomic island. These two effector genes, along with one other effector-like gene in the same region, are thus good candidates for being pathogenicity factors on citrus. Numerous gene content differences also exist between the three cankers strains, which can be correlated with their different virulence and host range. Particular attention was placed on the analysis of genes involved in biofilm formation and quorum sensing, type IV secretion, flagellum synthesis and motility, lipopolysacharide synthesis, and on the gene xacPNP, which codes for a natriuretic protein. Conclusion We have uncovered numerous commonalities and differences in gene content between the genomes of the pathogenic agents causing citrus canker A, B, and C and other Xanthomonas genomes. Molecular genetics can now be employed to determine the role of these genes in plant-microbe interactions. The gained knowledge will be instrumental for improving citrus canker control.
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    Phylogenomics of Xanthomonas field strains infecting pepper and tomato reveals diversity in effector repertoires and identifies determinants of host specificity
    Schwartz, Allison R.; Potnist, Neha; Milsina, Sujan; Wilson, Mark; Patane, Jose; Martins, Joaquim, Jr.; Minsavage, Gerald V.; Dahlbeck, Douglas; Akhunova, Alina; Almeida, Nalvo F.; Vallad, Gary E.; Barak, Jeri D.; White, Frank F.; Miller, Sally A.; Ritchie, David; Goss, Erica; Bart, Rebecca S.; Setubal, Joao C.; Jones, Jeffrey B.; Staskawicz, Brian J. (Frontiers, 2015-06-03)
    Bacterial spot disease of pepper and tomato is caused by four distinct Xanthomonas species and is a severely limiting factor on fruit yield in these crops. The genetic diversity and the type Ill effector repertoires of a large sampling of field strains for this disease have yet to be explored on a genomic scale, limiting our understanding of pathogen evolution in an agricultural setting. Genomes of 67 Xanthomonas euvesicatoria (Xe), Xanthomonas perforans (Xp), and Xanthomonas gardneri (Kg) strains isolated from diseased pepper and tomato fields in the southeastern and midwestern United States were sequenced in order to determine the genetic diversity in field strains. Type Ill effector repertoires were computationally predicted for each strain, and multiple methods of constructing phylogenies were employed to understand better the genetic relationship of strains in the collection. A division in the Xp population was detected based on core genome phylogeny, supporting a model whereby the host-range expansion of Xp field strains on pepper is due, in part, to a loss of the effector AvrBsT. Xp-host compatibility was further studied with the observation that a double deletion of AvrBsT and XopQ allows a host range expansion for Nicotiana benthamiana. Extensive sampling of field strains and an improved understanding of effector content will aid in efforts to design disease resistance strategies targeted against highly conserved core effectors.