RESUMO
Cacao swollen shoot virus (CSSV) is a major pathogen of cacao (Theobroma cacao) in Africa, and long-standing efforts to limit its spread by the culling of infected trees have had very limited success. CSSV is a particularly difficult virus to study, as it has a very narrow host range, limited to several tropical tree species. Furthermore, the virus is not mechanically transmissible, and its insect vector can only be used with difficulty. Thus, the only efficient means to infect cacao plants that have been experimentally described so far are by particle bombardment or the agroinoculation of cacao plants with an infectious clone. We have genetically transformed three non-host species with an infectious form of the CSSV genome: two experimental hosts widely used in plant virology (Nicotiana tabacum and N. benthamiana) and the model species Arabidopsis thaliana. In transformed plants of all three species, the CSSV genome was able to replicate, and, in tobacco, CSSV particles could be observed by immunosorbent electron microscopy, demonstrating that the complete virus cycle could be completed in a non-host plant. These results will greatly facilitate the preliminary testing of CSSV control strategies using plants that are easy to raise and to transform genetically.
Assuntos
Badnavirus/fisiologia , Cacau/virologia , Especificidade de Hospedeiro , Modelos Biológicos , Doenças das Plantas/virologia , Brotos de Planta/virologia , Badnavirus/genética , Badnavirus/ultraestrutura , DNA Viral/genética , Genoma Viral , Plantas Geneticamente Modificadas , Plasmídeos/metabolismo , Especificidade da Espécie , Nicotiana/genética , Nicotiana/virologiaRESUMO
Virus-resistant transgenic plants have been created primarily through the expression of viral sequences. It has been hypothesized that recombination between the viral transgene mRNA and the RNA of an infecting virus could generate novel viruses. As mRNA/viral RNA recombination can occur in virus-resistant transgenic plants, the key to testing this risk hypothesis is to compare the populations of recombinant viruses generated in transgenic and non-transgenic plants. This has been done with two cucumoviral systems, involving either two strains of cucumber mosaic virus (CMV), or CMV and the related tomato aspermy virus (TAV). Although the distribution of the sites of recombination in the CMV/CMV and TAV/CMV systems was quite different, equivalent populations of recombinant viruses were observed in both cases. These results constitute the first comparison of the populations of recombinants in transgenic and non-transgenic plants, and suggest that there is little risk of emergence of recombinant viruses in these plants, other than those that could emerge in non-transgenic plants.
Assuntos
Cucumovirus/genética , Genes Virais , Vírus de Plantas/genética , Plantas Geneticamente Modificadas/genética , Recombinação Genética , Sequência de Bases , Dados de Sequência Molecular , Plantas/genética , Plantas/virologia , Plantas Geneticamente Modificadas/virologia , Reprodutibilidade dos Testes , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Sensibilidade e EspecificidadeRESUMO
We report for the first time the production of acyl homoserine lactones (AHLs) by Erwina amylovora, an important quarantine bacterial pathogen that causes fire blight in plants. E. amylovora produces one N-acyl homoserine lactone [a N-(3-oxo-hexanoyl)-homoserine lactone or a N-(3-hydroxy-hexanoyl)-homoserine lactone] quorum sensing signal molecule both in vitro and in planta (pear plant). Given the involvement of AHLs in plant pathogenesis, we speculate that AHL-dependent quorum sensing could play an important role in the regulation of E. amylovora virulence.
Assuntos
4-Butirolactona/análogos & derivados , 4-Butirolactona/biossíntese , Erwinia amylovora/patogenicidade , Regulação Bacteriana da Expressão Gênica , Doenças das Plantas/microbiologia , Pyrus/microbiologia , Erwinia amylovora/crescimento & desenvolvimento , Erwinia amylovora/metabolismo , Transdução de Sinais , VirulênciaRESUMO
Quorum sensing is a cell-density-dependent regulatory mechanism which, in Gram-negative bacteria, usually involves the production and detection of N-acyl homoserine lactones (HSLs). In the last four years HSL-dependent quorum sensing has been identified in members of the Burkholderia cepacia complex, and this mini-review summarizes initial findings and discusses future perspectives.
Assuntos
4-Butirolactona/metabolismo , Proteínas de Bactérias/metabolismo , Burkholderia cepacia/metabolismo , Transdução de Sinais , 4-Butirolactona/análogos & derivados , Proteínas de Bactérias/genética , Burkholderia cepacia/genéticaRESUMO
Quorum sensing is a regulatory mechanism (operating in response to cell density) which in gram-negative bacteria usually involves the production of N-acyl homoserine lactones (HSL). Quorum sensing in Burkholderia cepacia has been associated with the regulation of expression of extracellular proteins and siderophores and also with the regulation of swarming and biofilm formation. In the present study, several quorum-sensing-controlled gene promoters of B. cepacia ATCC 25416 were identified and characterized. A total of 28 putative gene promoters show CepR-C(8)-HSL-dependent expression, suggesting that quorum sensing in B. cepacia is a global regulatory system.