2007 Fiscal Year Final Research Report Summary
Characterization of a male-killing virus and its mode of action in Homona magnanima
| Project/Area Number |
17208006
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied entomology
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| Research Institution | Tokyo University of Agriculture and Technology |
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Principal Investigator |
KUNIMI Yasuhisa Tokyo University of Agriculture and Technology, Graduate School, Institute of Symbiotic Science and Technology, Professor (50195476)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAI Madoka Tokyo University of Agriculture and Technology, Graduate School, Institute of Symbiotic Science and Technology, Associate Professor (60302907)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Homona magnanima / late male-killing / sex-ratio distorters / RNA virus / prevalence / RT-PCR / late male-killing |
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| Research Abstract |
Maternally inherited female-biased sex ratios have been documented in many invertebrate species. One cause of such biased sex ratios is male-killing ; that is, only males die. In most species, male-killing occurs during embryonic stages (early male-killing) and is associated with cytoplasmic bacteria. However, the oriental tea tortrix, Homona magnanima, is one of the few species in which male death occurs in the larval or pupal stage, and is thus an example of late male-killing. In this study, we examined the gross morphology and histopathology of a late male-killing strain (LMK) of H. magnanima larvae, and spatial and temporal dynamics of the agent in natural populations of H. magnanima, and partially purified the agent causing late male-killing in H. magnanima.
Most male LMK larvae died during the last instar or pupal stage, and dead male larvae showed characteristic signs and symptoms of male-killing. The body color of male LMK larvae started to change 4 days after molting into the f
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ifth instar and became increasingly opaque white. Male LMK larvae weighed significantly less than normal strain (NSR) males. Midgut cells of male LMK larvae were discharged into the lumen as granules at 7 days after the final molt, and dropped into the lumen just before death. The fat body of male LMK larvae contained large fat granules in the cytoplasm but became a tumorlike cell mass that finally fused with the epidermal cells.
To identify the late male-killing agent, we purified a causal agent from male LMK larvae by sucrose gradient ultracentrifugation. Injection experiment revealed that the purified fraction contained the late male-killing agent, and electron microscopy showed that the purified fraction has isometric particles of 10-15 nm in diameter. Nucleic acids in the purified fraction were degraded by RNase A but not by DNase I, which suggests that nucleic acids in the purified fraction were RNAs but not DNAs. LMK specific two RNA sequences, MK1068 and MK1241, were identified from the purified fraction. A BLAST research revealed that their nucleotide and deduced amino acid sequences did not match any other known sequences. These results suggested that male-killing in H. magnanima may be caused by a new RNA virus. This RNA virus was detected from H. magnanima larvae collected in Miyazaki, Gifu, Shizuoka, Saitama and Ibaragi Prefectures. Less
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Research Products
(21 results)
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[Presentation] Identification of the agent causing late male-killing in the oriental tea tortrix, Homona mnanima using specific RNA sequences2007
Author(s)
K., Nakanishi, M., Hoshino, H., Koyama, M., Nakai, Y., Kunimi
Organizer
51th Annual Meeting of Japanese Society of Applied Entomology and Zoology
Place of Presentation
Hiroshima University
Year and Date
20070327-29
Description
「研究成果報告書概要(欧文)」より
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