There are some R genes against potyviruses which were mapped in pepper. However, none of them has been characterized at the molecular level. In this study, we characterized Pvr9 which is an Rpi-blb2 ortholog from pepper and confers a hypersensitive response to Pepper mottle virus (PepMoV) in a transient expression system in Nicotiana benthamiana. This gene putatively encoded for 1298 amino acids and is located on pepper chromosome 6. PepMoV NIb was the elicitor of the Pvr9-mediated hypersensitive response. NIb from several other potyviruses also elicited the hypersensitive response. Inoculation of pepper with PepMoV resulted in a minor increase in Pvr9 transcription in the resistant cultivar CM334 and a slight down-regulation in the susceptible cultivar Floral Gem. The 5' upstream region of Pvr9 from cultivar CM334 had higher transcription activity than the region from cultivar Floral Gem. The cultivars CM334 and Floral Gem had non-functional Pvr9 homologs with loss-of-function mutations.
Soybean mosaic virus (SMV), a member of the genus Potyvirus, significantly reduces soybean production worldwide. Rsv3, which confers strain-specific resistance to SMV, was previously mapped between the markers A519F/R and M3Satt in chromosome 14 of the soybean [Glycine max (L.) Merr.] genotype L29. Analysis of the soybean genome database revealed that five different NBS-LRR sequences exist between the flanking markers. Among these candidate Rsv3 genes, the full-length cDNA of the Glyma.14g204700 was successfully cloned from L29. Over-expression of Glyma.14g204700 in leaves inoculated with SMV inhibited viral infection in a soybean genotype lacking Rsv3. In addition, the transient silencing of the candidate gene caused a high accumulation of an avirulent strain in L29 carrying Rsv3. Our results therefore provide additional line of evidence to support that Glyma.14g204700 is likely Rsv3 gene that confers strain-specific resistance to SMV.
The pabA gene in Escherichia coli and Salmonella typhimurium encodes the glutamine amidotransferase subunit of para-aminobenzoate synthase, which catalyzes the first reaction in the conversion of chorismate to para-aminobenzoate (PABA). We have determined the nucleotide sequences of 1,362 base pairs preceding E. coli pabA and of 981 base pairs preceding S. typhimurium pabA. The nucleotide sequences suggest the presence of two protein-coding regions immediately upstream of pabA, designated orfl and fic. Transcription analysis indicates that E. coli pabA is encoded by two overlapping transcriptional units. The polycistronic transcriptional unit includes orfl-fic-pabA and is initiated by the promoter designated P2. The monocistronic unit includes only pabA and is initiated by the promoter designated P1, which is located in the fic-coding regioI.Both promoters transcribe pabA to about the same steady-state level. However, expression analysis using chromosomal pabA-lacZ translational fusions indicated that P1 expressed PabA at least 50-fold more efficiently than P2. pabA-dependent growth rate analysis indicates that P1 is essential and P2 is dispensable for PABA metabolism. In the absence of P1, growth was reduced as a result of insufficient PabA expressed from P2. The significance of these results and possible posttranscriptional control mechanisms which affect PabA expression from the P2-initiated polycistronic unit are discussed.para-Aminobenzoate synthase (PABS) catalyzes the conversion of chorismate and glutamine to an unidentified intermediate which is converted to para-aminobenzoate (PABA) by a second enzyme (29a). The two subunits of PABS are encoded by two unlinked genes: pabB, at 40 min on the Escherichia coli map (15, 43), which encodes the larger 54,000-molecular-weight subunit that catalyzes the synthesis of the unidentified intermediate from chorismate and NH4' (12,39), and pabA, at 74 min (14, 15), which encodes a 21,000-molecular weight glutamine-amidotransferase subunit that allows PABS to use glutamine as the source of NH4' (19). The gene(s) encoding the second enzyme has not been identified or mapped.The regulation of the genes encoding PABS is unknown. PABA is essential for the biosynthesis of dihydrofolate, which in various forms participates in the synthesis of purines, pyrimidines, formylmethionyl-tRNA, and some amino acids and vitamins. As the folate moiety is not consumed during the reactions, the de novo synthesis requirements for dihydrofolate and its precursors are small. Also, since exogeneous folates cannot be transported and used by E. coli, dihydrofolate synthesis is essential, but only at replenishment levels as a cell grows and divides. Because pabA and pabB are unlinked to one another and to other known fol genes (6,8,35), the question of how they are regulated arises. Before this question can be answered, however, more information on the organization of each particular gene and its expression signals is required.The nucleotide sequences of pabA from E. coli, Salmonella typhimurium,...
Tomato (Lycopersicum esculentum L.) and pepper (Capsicum annuum L.) plants belonging to the family Solanaceae are cultivated worldwide. The rapid development of next-generation sequencing (NGS) technology facilitates the identification of viruses and viroids infecting plants. In this study, we carried out metatranscriptomics using RNA sequencing followed by bioinformatics analyses to identify viruses and viroids infecting tomato and pepper plants in Vietnam. We prepared a total of 16 libraries, including eight tomato and eight pepper libraries derived from different geographical regions in Vietnam. We identified a total of 602 virus-associated contigs, which were assigned to 18 different virus species belonging to nine different viral genera. We identified 13 different viruses and two viroids infecting tomato plants and 12 viruses and two viroids infecting pepper plants with viruses as dominantly observed pathogens. Our results showed that multiple infection of different viral pathogens was common in both plants. Moreover, geographical region and host plant were two major factors to determine viral populations. Taken together, our results provide the comprehensive overview of viral pathogens infecting two important plants in the family Solanaceae grown in Vietnam.
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