RESUMO
The nodulation genes of Bradyrhizobium japonicum are essential for infection and establishment of a nitrogen-fixing symbiosis. Here, we demonstrate that plant-produced isoflavones induce nodulation gene expression in a population density-dependent fashion. Nodulation gene induction is highest at a low population density and significantly reduced in more dense cultures. A quorum signal molecule in the conditioned medium of B. japonicum cultures mediates this repression. Repression in response to the quorum signal results from the induction of NolA which, in turn, induces NodD2 leading to inhibition of nod gene expression. Consistent with this, nolA-lacZ and nodD2-lacZ expression increased with increasing population density. Unlike the wild type, the ability to induce nodY-lacZ expression did not decline with population density in a NolA mutant. Normally, nod gene expression is repressed in planta (i.e. within nodules). However, expression of a nodY-GUS fusion was not repressed in a NolA mutant, suggesting that quorum-sensing control may mediate in planta repression of the nod genes. Addition of conditioned medium to cultures significantly reduced nod gene expression. Treatment of inoculant cultures with conditioned medium also reduced the ability of B. japonicum to nodulate soybean plants.
Assuntos
Proteínas de Bactérias/genética , Bradyrhizobium/genética , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Isoflavonas/metabolismo , Fatores de Transcrição , Proteínas de Bactérias/metabolismo , Bradyrhizobium/citologia , Bradyrhizobium/efeitos dos fármacos , Bradyrhizobium/fisiologia , Meios de Cultivo Condicionados/química , Meios de Cultivo Condicionados/farmacologia , Inibidores Enzimáticos/farmacologia , Fabaceae/microbiologia , Genes Reporter/genética , Genisteína/farmacologia , Óperon , Raízes de Plantas/microbiologia , Densidade Demográfica , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Glycine max/microbiologia , Simbiose/fisiologia , Ativação TranscricionalRESUMO
Transgenic plants of the model legume Lotus japonicus were regenerated by hypocotyl transformation using a bar gene as a selectable marker. The bar encodes for Phosphinothricin Acetyl Transferase that detoxifies phosphinothricin (PPT), the active ingredient of herbicides such as Ignite (AgrEvo) and Basta (Hoechst). Transgenic L. japonicus plants resistant to PPT were positive upon PCR by bar gene-specific primers. In 5 out of 7 independent lines tested, PPT resistance segregated as a single dominant allele indicating a single T-DNA insertion into the plant genome. All regenerated plants were fertile and void of visible somaclonal abnormalities contrary to 14% infertility when antibiotic selectable markers were used. The lack of somaclonal variation, ease of PPT application and low cost of PPT makes this protocol an attractive alternative for the regeneration of transgenic L. japonicus. The production of PPT herbicide-resistant L. japonicus plants may have significant commercial applications in crop production.
Assuntos
Acetiltransferases/genética , Aminobutiratos/metabolismo , Fabaceae/genética , Herbicidas/farmacologia , Plantas Medicinais , Acetiltransferases/metabolismo , Técnicas de Cultura , DNA Bacteriano/genética , DNA de Plantas , Resistência a Medicamentos/genética , Fabaceae/efeitos dos fármacos , Genes de Plantas , Marcadores Genéticos , Herbicidas/metabolismo , Plantas Geneticamente Modificadas , Reação em Cadeia da Polimerase , Transformação GenéticaRESUMO
We constructed a BAC library of the model legume Lotus japonicus with a 6-to 7-fold genome coverage. We used vector PCLD04541, which allows direct plant transformation by BACs. The average insert size is 94 kb. Clones were stable in Escherichia coli and Agrobacterium tumefaciens.
Assuntos
Agrobacterium tumefaciens/genética , Cromossomos Artificiais Bacterianos/genética , DNA de Plantas/genética , Genoma de Planta , Magnoliopsida/genética , Southern Blotting , Clonagem Molecular , DNA de Plantas/análise , Escherichia coli/genética , Vetores Genéticos , Reação em Cadeia da Polimerase , Transformação GenéticaRESUMO
Arthritis was produced in adult albino rats weighing 120+-10g through intramuscular injections of 0.5ml of 2 percent w/w formalin beneath the plantar aponeurosis on the first and third day. The anterioposterior diameter of the ankle was recorded and statistically analyzed. It was evident that relatively low doses, 0.25ml/100g body weight, of tincture of Hypericum perforatum produced a significant 48 percent anti-inflammatory effect, whereas higher doses, 0.5ml/100g body weight, of the drug showed 32 percent activity under identical conditions. Parallel studies with 1mg/100g body weight hydrocortisone administration gave similar anti-inflammatory effects. Local application of an alcoholic extract of the drug in very small doses also produced significant skin softness and flexiblility of muscle
