RESUMO
A prevailing opinion is that the strains of Pseudomonas aeruginosa that infects both plants and humans are two separate species. This study strongly disputes that notion until the modern molecular technology proves otherwise. This paper examines a spectrum of strains occurring in nature, their habitats, dissemination, their relationship to clinical strains, and the environmental conditions that favor their colonization of plants. The isolates were obtained from clinical specimens, plants, soil, and water. The identity of these strains was confirmed using pyocin typing and biochemical assays. The data reveal that agricultural soils, potted ornamental plants, hoses, fountains, and faucets frequently harbored P. aeruginosa. However, it was not commonly found in semi-arid areas, suggesting that moisture and high humidity is necessary for colonization and survival. Though found in soil, P. aeruginosa was seldom isolated on edible plant parts. The pathogenicity of various strains on plants was tested by inoculating vegetables, lettuce slices (Lactuca sativa L. "Great Lakes"), celery stalks (Apium graveolens L. var. Dulce], potato tuber slices (Solanum tuberosum L. "Whiterose"), tomato (Lycopersicon esculentum L. Mill), cucumber (Cucumis sativus L.), rutabaga (Brassica campestris L.), and carrot (Daucus carota L. var sativa). There was considerable variation in the strains' ability to cause rot, but no difference was observed between clinical isolates and others from agricultural fields, water, and soil. Two of the clinical isolates from burn patients, P. aeruginosa PA13 and PA14, exhibited the greatest virulence in causing rot in all the plants that were tested, especially on cucumber, lettuce, potato, and tomato. The study discusses how closely the epidemiology of P. aeruginosa relates to many plant pathogens, and the ability of human isolates to colonize plants and food material under favorable conditions. The biochemical and phenotypic similarity among strains from the clinical and agricultural material is strongly indicative that they are the same species and that plants and soil are natural reservoirs for P. aeruginosa.
Assuntos
Produtos Agrícolas/microbiologia , Pseudomonas aeruginosa/isolamento & purificação , Pseudomonas aeruginosa/patogenicidade , Microbiologia do Solo , Apium/microbiologia , Brassica napus/microbiologia , Cucumis sativus/microbiologia , Daucus carota/microbiologia , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Lactuca/microbiologia , Solanum lycopersicum/microbiologia , Doenças das Plantas/microbiologia , Solanum tuberosum/microbiologia , Verduras/microbiologia , Microbiologia da ÁguaRESUMO
Tomato leaf curl Taiwan virus (ToLCTWV) and Tomato spotted wilt virus (TSWV) are two major tomato viruses that cause serious economic losses. In this study, a partial C2 gene from ToLCTWV and the middle half of the N gene of TSWV were fused as a chimeric transgene to develop multiple virus resistance in transgenic plants. This construct was introduced into Nicotiana benthamiana and tomato by Agrobacterium-mediated transformation. Several transgenic lines showed no symptom post agro-inoculation with ToLCTWV and displayed high resistance to TSWV. The detection of siRNAs indicated that the resistance was via RNA silencing. This study demonstrated that linkage of gene segments from two viruses with distinct genomic organization, one DNA and the other RNA, can confer multiple virus resistance in transgenic plants via gene silencing.
Assuntos
Vírus de DNA/fisiologia , Proteínas do Nucleocapsídeo/genética , Plantas Geneticamente Modificadas/virologia , Proteínas Recombinantes de Fusão/genética , Solanum lycopersicum/virologia , Tospovirus/fisiologia , Proteínas Virais/genética , Vírus de DNA/genética , Solanum lycopersicum/genética , Doenças das Plantas/genética , Doenças das Plantas/virologia , Folhas de Planta/genética , Folhas de Planta/virologia , Plantas Geneticamente Modificadas/genética , Interferência de RNA , Vírus de RNA/genética , Vírus de RNA/fisiologia , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Nicotiana/genética , Nicotiana/virologia , Tospovirus/genética , TransgenesRESUMO
Development of effective disease-resistance to a broad-range of pathogens in crops usually requires tremendous resources and effort when traditional breeding approaches are taken. Genetic engineering of disease-resistance in crops has become popular and valuable in terms of cost and efficacy. Due to long-lasting and broad-spectrum of effectiveness against pathogens, employment of systemic acquired resistance (SAR) for the genetic engineering of crop disease-resistance is of particular interest. In this report, we explored the potential of using SAR-related genes for the genetic engineering of enhanced resistance to multiple diseases in tomato. The Arabidopsis NPR1 (nonexpresser of PR genes) gene was introduced into a tomato cultivar, which possesses heat-tolerance and resistance to tomato mosaic virus (ToMV). The transgenic lines expressing NPR1 were normal as regards overall morphology and horticultural traits for at least four generations. Disease screens against eight important tropical diseases revealed that, in addition to the innate ToMV-resistance, the tested transgenic lines conferred significant level of enhanced resistance to bacterial wilt (BW) and Fusarium wilt (FW), and moderate degree of enhanced resistance to gray leaf spot (GLS) and bacterial spot (BS). Transgenic lines that accumulated higher levels of NPR1 proteins exhibited higher levels and a broader spectrum of enhanced resistance to the diseases, and enhanced disease-resistance was stably inherited. The spectrum and degree of these NPR1-transgenic lines are more significant compared to that of transgenic tomatoes reported to date. These transgenic lines may be further explored as future tomato stocks, aiming at building up resistance to a broader spectrum of diseases.
