SUMMARY We previously reported that cell wall protein fractions (CWPs) of the biocontrol agent Pythium oligandrum have elicitor properties in sugar beet and wheat. Here we have examined the effect of treatment with the D-type of CWP, a fraction that contains two major forms (POD-1 and POD-2), on the induction of defence-related genes in sugar beet. Using PCR-based cDNA library subtraction, we identified five genes that were highly expressed in response to CWP treatment. The five genes are probably of oxalate oxidase-like germin (OxOLG), glutathione S-transferase (GST), 5-enol-pyruvylshikimate-phosphate synthase (EPSPS), phenylalanine ammonia-lyase (PAL) and aspartate aminotransferase (AAT). In addition, we purified and characterized POD-1 and POD-2 and found that POD-1 induced all five genes, whereas POD-2 induced three of the genes, but not OxOLG or GST. A sugar beet bioassay indicated that CWP, POD-1 and POD-2 are each sufficient to induce resistance to sugar beet seedling disease caused by Aphanomyces cochlioides. Although carbohydrate analyses indicated that POD proteins were glycoproteins with similar carbohydrate compositions, containing approximately 15.0% carbohydrate by weight, their peptide portions have elicitor activity. Furthermore, cDNAs of POD-1 and POD-2 proteins were cloned, and the deduced amino acid sequences were found to be 82.9% identical. Characterization of their molecular structures indicated that they have an elicitin domain followed by a C-terminal domain with a high frequency of Ser, Thr, Ala and Pro, which is structurally similar to class III elicitins. However, phylogenetic analysis with 22 representative elicitin and elicitin-like proteins showed that POD-1 and POD-2 are distinct from previously defined elicitin and elicitin-like proteins. Therefore, POD-1 and POD-2 are novel oomycete cell wall elicitin-like glycoproteins.
Hepatitis C virus (HCV) genotype 3a infection poses a serious health problem worldwide. A significant association has been reported between HCV genotype 3a infections and hepatic steatosis. Nevertheless, virological characterization of genotype 3a HCV is delayed due to the lack of appropriate virus cell culture systems. In the present study, we established the first infectious genotype 3a HCV system by introducing adaptive mutations into the S310 strain. HCV core proteins had different locations in JFH-1 and S310 virus-infected cells. Furthermore, the lipid content in S310 virus-infected cells was higher than Huh7.5.1 cells and JFH-1 virus-infected cells as determined by the lipid droplet staining area. Conclusion: This genotype 3a infectious cell culture system may be a useful experimental model for studying genotype 3a viral life cycles, molecular mechanisms of pathogenesis, and genotype 3a-specific antiviral drug development.
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