Study on Infection and Multiplication of Densonucleosis Virus of Silkworm, Bombyx mori L.

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Studies on densonucleosis virus of silkworm, Bombyx mori, (BmDNV) which is divided into BmDNV-1, Ina-DNV, and BmDNV-2, Yamanashi-DNV (yDNV) and Chinese-DNV (cDNV), had been carried out for three years since 1988. The following results were obtained.1. Dot-IGSS method was used in order to detect earlier infection with cDNV. The virus infection was detected ten hours after virus inoculation. The sensitivity showing positive reaction was high and 10ng.2. In the mixed infection of cDNV and NPV or CPV, higher degree of interference between cDNV and NPV was shown.3. Restriction enzyme mapping of the two DNAs, DNA-1 (6.56Kb) and DNV-2 (6.07Kb), of cDNV was tried. Some differences in base sequence between the two DNAs were found.4. yDNV and cDNV are closely related viruses. Between the DNAs of the two DNVs, the nucleotide sequence of the terminal region was almost same. However, the restriction pattern of the cDNV DNA was different from that of the yDNV DNA.5. Cloning of cDNV DNA-1 (6.56Kb) wa … More s tried. Genom DNA bearing the complete length was inserted into pUC119 plasmid vector and the making clone was succeeded.6. Cloning of BmDNV-1 (4.9Kb) was carried out. By inserting genom DNA bearing the perfect length into pUC119 plasmid vector, clone was obtained. And by using clone p17238, all base sequence bearing 5048 nucleotides was analyzed.7. cDNV had 5 structural proteins showing the molecular weight of 41, 43, 48, 51 and 100Kd, respectively, on SDS-PAGE gel. It was clarified that cDNV contained polyamine of spermidine, spermine and putrescine.8. The complete sequence of the DNV DNA (5048 nucleotides) has inverted repeats of 225 nucleotides and the terminal 153 nucleotides are palindromic. The palindromes can fold back on themselves to form a hairpin structure but, unlike AAV, the small internal palidrome which forms a T-shaped conformation was observed.9. Two insect cell lines were persistently infected ; one with isometric ssDNA virus 20nm in diameter and the other with an isometric ssRNA virus 22nm in diameter.10. Iarvae of the mulberry pylarid, Glyphodes pyloalis, which infest mulberry plantations, are frequently infected in a chronic state with nonoccluded viruses that are serologically indistinguishable from the BmDNVs. The results suggest that the BmDNV originated from the lyphodes nonoccluded viruses, and epizootiologically, the mulberry pyralid is a common habitual host of these nonoccluded viruses. Less