Jun-Mo Cho

Antiviral Effects of the Culture Filtrate from Serratia marcescens Gsm01, against Cucumber mosaic virus (CMV)

The potential antiviral effects of the culture filtrates (CF) from Serratia marcescens strain Gsm01 against yellow strain of Cucumber mosaic virus (CMV-Y) were investigated. The culture filtrate of S. marcescens strain Gsm01 applied on Chenopodium amaranticolor showed high inhibitory activity, likewise no necrosis appeared when applied on the tobacco plants 2 days before CMV-Y inoculation. When plants were challenge inoculated with CMV-Y for eighteen days, the disease incidence in plants with culture filtrate of S. marcescens Gsm01 did not exceed 59%, whereas 100% of control plants were severely infected. The results of double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA), reverse transcriptase polymerase chain reaction (RT-PCR), dot blotting, and western blotting showed that culture filtrate treatment highly affected the accumulation of CMV-Y or its CP protein gene in the treated plant leaves. It was also observed that the culture filtrate had no RNase activity on genomic RNAs of CMV-Y, suggesting that culture filtrate may not contain ribosome inactivating proteins (RIPs) or proteins with RNase activity. These data shows that culture filtrate of S. marcescens strain Gsm01 seems to be a promising source of antiviral substance for the practical use.

Identification of a Genetic Locus Related to Antivirus Production in Pseudomonas fluorescence strain Gpf01 Against Cucumber mosaic virus

Pseudomonas fluorescens strain Gpf01, isolated from ginseng rhizosphere showed antiviral activity against Cucumber mosaic virus, when tested in a local host of CMV, Chenopodium amaranticolor. Transposon mutant library of Gpf01 was prepared using pGS9::Tn5 and the mutant Gpf01-RS19 was found to loose antiviral production. We developed primers from the flanking region of Tn5 and found a cosmid clone pAV1123, harboring 1.2 kb antiviral compound producing (avcf01) locus. When a sub-clone pPH9, which carried 9.3 kb region of pAV1123, was introduced into antivirus deficient P. fluorescens wild type strain B16, it exhibited antiviral activity. Using Tn3-gus mutagenesis and complementation analysis, it was found that the genes related to antiviral activity production resided in a 9.3 kb HindIII-HindIII fragment of pAV1123, indicating that the plasmid carries an essential genes promoting antiviral activity.

Characterization of Streptomyces Species Causing Potato Scab in Korea: Distribution, Taxonomy, and Pathogenicity

From 1996 to 1999, potato-growing areas in Korea were surveyed for identification and distribution of potato scab pathogens. Potato scab was widely distributed in the mass cultivation areas, especially in Jriu island, southern areas of Chonnam and Gyounggi provinces, and the alpine area of Gangwon province. Jeju island was the most affected area by this disease. A total of 55 Streptomyces strains were isolated from potato scab lesions, among which 40 strains were pathogenic on progeny tubers. Among the pathogenic strain, 21 strains were identified as previously described S. scabies, 7 Strains as S. turgidiscabies, and 5 Strains as S. acidiscabies, while 7 strains were observed as having distinct phenotypic properties. These strains were classified into six distinct clusters based on phenotypic characteristics and selected representative strains for each cluster. S. scabies (S33) had grey spores in a spiral chain. Mean-while, S. turgidiscabies (S27) had grey spores, S. acidiscabies (S71) had white spores, S. luridiscabiei (S63) had yellow-white spores, S. puniciscabiei (S77) had purple-red spores, and S. niveiscabiei (S78) had thin and compact white spores, all in a rectiflexuous chain. Pathogenicity was determined by the production of thaxtomin A and homologs of necl and ORFtnp genes. In TLC, representative strains S27, S71, S63, S77, and S78 produced a yellow band that co-migrated with the authentic thaxtomin A. However, thaxtomin A was not detected in chloroform extracts from oatmeal broth culture and Slice tuber tissue of S. luridiscabiei (S63) and S. puniciscabiei (S77) by HPLC analysis. In addition, no homologs of necl and ORFtnp genes in S. acidiscabies (S71), S. luridiscabiei (S63), S. puniciscabiei (S77), and S. niveiscabiei (S78) were detected by PCR and Southern hybridization analysis.