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Soybean mosaic virus (SMV)-CN18 is an Rsv resistance-breaking (RB) isolate to overcome soybean resistance genes Rsv1, Rsv3 and Rsv4. The aim of this study was to characterize nuclear inclusion protein a (NIa protein) of RB isolate at the molecular level and demonstrate its processing into genome-linked protein (VPg) and NIa-Pro domains in Esherichia coli containing a bacterial expression pET vector inserted with NIa gene. The full-length of NIa gene was synthesized by reverse transcription-polymerase chain reaction (RT-PCR) and its 1298 nucleotides (nt) and 432 amino acids (aa) were deduced. The nt and aa sequences of NIa gene of SMV-CN18 shared high identities with the corresponding sequences of the NIa gene of the known SMV isolates, suggesting that the NIa is a highly conserved protein. The NIa-Pro domain contains a highly conserved structural motif for proteolysis, while the VPg domain contains a nuclear localization signal (NLS), a putative NTP-binding site and cellular factor-binding sites. The phylogenetic tree revealed that less divergence of NIa protein exists among twelve SMV isolates, which can be supported by a low bootstrap value between clades. In addition, the full-length of NIa gene, amplified by RT-PCR, was ligated into pET-28b E. coli expression vector with an N-terminal His6-tag. Optimal conditions for expression were at 1mM treatment of IPTG at 25°C for 5 hr. The released protein from bacterial lysates remained soluble and proved the processing form of the NIa polyprotein. E. coli expression system shows the processed product of 29 kDa VPg in SDS-PAGE confirmed by western blot analysis in both crude extracts and purified elution products, using Ni2+-NTA resin. The present study indicates that the N-terminal region of NIa which is processed and expressed in bacteria.

Several Korean medicinal plants were selected to evaluate for free radical scavenging capacities and antioxidant activities using commonly accepted assays. They were extracted with dichloromethane, methanol or ethanol, respectively and selected for the best antioxidant results. Flavonoids, such as catechin, morin, naringenin, quercetin and rutin, were included and used as standards in this study. Each sample under assay condition showed a dose-dependent free radical scavenging effect of DPPH (1,1-diphenyl-2-picryl hydrazyl radical) and a dose-dependent inhibitory effect of xanthine oxidase and lipid peroxidation. Among plant extracts, the root bark of Morus alba and the leaf of Saururus chinensis showed stronger SC50 or ID50 values than other plant extracts. They also showed a protective effect on DNA damage caused by hydroxyl radicals generated from UV-induced photolysis of hydrogen peroxide. A rapid evaluation for antioxidants using TLC screening and DPPH staining methods demonstrated each plant extract having various free radical scavenging capacity. Stained silica layer revealed a purple background with yellow spots at the location of drops, which showed radical scavenging capacity. The intensity of the yellow color depends upon the amount and nature of radical scavenger present in the samples. This antioxidant potential corresponded with the results of DPPH spectrophotometric assay.