RESUMO
Infectious cDNA clones are an important tool to study the molecular and cellular process of RNA virus infection. In vitro and in vivo transcription systems are the two main strategies used in the generation of infectious cDNA clones for RNA viruses. This study describes the first generation of a full-length infectious cDNA clone of Cowpea mild mottle virus (CPMMV), a Carlavirus. The full-length genome was synthesized by Overlap Extension PCR of two overlapping fragments and cloned in a pUC-based vector under control of the SP6 RNA polymerase promoter. After in vitro run-off transcription, the produced RNA was mechanically inoculated into soybean plants cv. CD206. The systemic infection was confirmed by RT-PCR and further sequencing of amplified cDNA fragments. To simplify the transfection process, the complete genome was subcloned into a binary vector under control of the 35S promoter of cauliflower mosaic virus by the Gibson Assembly protocol. The resulting clones were inoculated by particle bombardment onto soybean seedlings and the recovery of the virus was confirmed 2 weeks later by RT-PCR. Our results indicate the constructs of the full-length cDNA of CPMMV are fully infectious in both in vitro and in vivo transcription strategies.
Assuntos
Carlavirus/genética , DNA Complementar , Genoma Viral , Clonagem Molecular , Ordem dos Genes , Fases de Leitura Aberta , Doenças das Plantas/virologia , Glycine max/virologiaRESUMO
Infectious cDNA clones of RNA viruses are important tools to study molecular processes such as replication and host-virus interactions. However, the cloning steps necessary for construction of cDNAs of viral RNA genomes in binary vectors are generally laborious. In this study, a simplified method of producing an agro-infectious Pepper mild mottle virus (PMMoV) clone is described in detail. Initially, the complete genome of PMMoV was amplified by a single-step RT-PCR, cloned, and subcloned into a small plasmid vector under the T7 RNA polymerase promoter to confirm the infectivity of the cDNA clone through transcript inoculation. The complete genome was then transferred to a binary vector using a single-step, overlap-extension PCR. The selected clones were agro-infiltrated to Nicotiana benthamiana plants and showed to be infectious, causing typical PMMoV symptoms. No differences in host responses were observed when the wild-type PMMoV isolate, the T7 RNA polymerase-derived transcripts and the agroinfiltration-derived viruses were inoculated to N. benthamiana, Capsicum chinense PI 159236 and Capsicum annuum plants.
Assuntos
Clonagem Molecular/métodos , DNA Complementar/genética , Vetores Genéticos/genética , Vírus de RNA/genética , Tobamovirus/genética , RNA Polimerases Dirigidas por DNA/genética , RNA Polimerases Dirigidas por DNA/metabolismo , Genoma Viral/genética , Doenças das Plantas/genética , Regiões Promotoras Genéticas/genética , RNA Viral/genética , Nicotiana/virologia , Proteínas Virais/genética , Proteínas Virais/metabolismoRESUMO
The gene dhaT from Klebsiella pneumoniae encoding 1,3-propanediol oxidoreductase (PDOR) was de novo synthesized by splicing overlap extension polymerase chain reaction (SOE-PCR) primarily according to Escherichia colis codon usage, as well as mRNA secondary structure. After optimization, Codon Adaptation Index (CAI) value was improved from 0.75 to 0.83, meanwhile energy of mRNA secondary structure was increased from -400.1 to -86.8 kcal/mol. This synthetic DNA was under control by phage T7 promoter in the expression vector pET-15b and transformed into the E. coli BL21 (DE3) strain. Inducers such as isopropyl beta-D-thiogalactoside (IPTG) and lactose were compared by activity at different inducing time. The activity of PDOR after codon optimized was 385.4 +/- 3.6 U/mL, which was almost 5-fold higher than wild type (82.3 +/- 1.5 U/ml) under the flask culture at 25ºC for 10 hrs. Then his-tagged enzyme was separated by using Ni-IDA column. The favorite environment for enzyme activity was at 5°C and pH 10.0, PDOR showed a certainly stability in potassium carbonate buffer for 2 hrs at diverse temperatures, enzyme activity was significantly improved by Mn2+.