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Updated: Jun 4, 2025
Mass-Rearing and Molecular Studies in Tortricidae Pest Insects
Published on: March 25, 2022
Infection pattern of male-killing viruses alters phenotypes in the tea tortrix moth Homona magnanima
Takumi Takamatsu1, Hiroshi Arai2,3, Yoshiyuki Itoh4
1United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai, Fuchu, Tokyo, 183-8509, Japan. s229249y@st.go.tuat.ac.jp.
Abstract:
Male-killing is a microbe-induced reproductive manipulation in invertebrates whereby male hosts are eliminated during development. In the tea tortrix moth Homona magnanima, Osugoroshi viruses 1‒3 (OGVs), belonging to Partitiviridae induce male-killing. The infection patterns of OGVs are diverse; however, how the influence of these patterns of host phenotypes remains largely unknown. Using field-collected larvae, we established a OGV1 and OGV3 double-infection line, in addition to a triple-infection line, and examined the dsRNA segments, purified viral proteins, OGV density, and host phenotypes. PCR analysis demonstrated that the triple-infection line lost one dsRNA segment, whereas the double-infection line lost eight segments, including one RNA-dependent RNA polymerase (RdRp) gene. LC-MS analysis revealed three potential structural proteins in the OGVs. Males died at the larval stage in the triple-infection line and at the embryo-larval stage in the double-infection line of OGV1 and OGV3; the RNA load of female parents did not contribute to the developmental stage at which males died. These findings indicate that the pattern of viral infection, rather than viral RNA load transmitted from female parent, controls the stage of development at which male-killing occurs. Furthermore, the duration of the larval stage of the double-infection line was found to be significantly longer than that of the triple-infection line. The shorter duration of the larval stage of the triple-infection line could be advantageous over the double-infection line in maximizing transmission efficiency.
Insights
Male-killing viruses in the tea tortrix moth show diverse infection patterns. Viral segment loss, not RNA load, dictates when males die, impacting transmission efficiency.
Area of Science:
- Microbiology
- Genetics
- Insect Pathology
Background:
- Male-killing is a reproductive manipulation in invertebrates caused by microbial infections.
- Osugoroshi viruses (OGVs) 1-3 in the tea tortrix moth (Homona magnanima) are known to induce male-killing.
- The impact of diverse OGV infection patterns on host phenotypes is not well understood.
Purpose of the Study:
- To investigate how different Osugoroshi virus (OGV) infection patterns influence male-killing in the tea tortrix moth.
- To determine the relationship between viral genetic makeup and the developmental stage of male lethality.
- To assess the role of viral RNA load in male-killing and its transmission.
Main Methods:
- Established double- (OGV1+OGV3) and triple-infection (OGV1+OGV2+OGV3) lines from field-collected larvae.
- Analyzed viral dsRNA segments using PCR.
- Identified viral proteins using LC-MS.
- Quantified OGV density and examined host phenotypes, including male lethality and larval duration.
Main Results:
- The triple-infection line lost one dsRNA segment, while the double-infection line lost eight segments, including an RNA-dependent RNA polymerase (RdRp) gene.
- LC-MS identified three potential structural proteins in OGVs.
- Males died at the larval stage in the triple-infection line and at the embryo-larval stage in the double-infection line.
- Male-killing stage was determined by the viral infection pattern, not the parental RNA load.
- The double-infection line exhibited a significantly longer larval stage duration compared to the triple-infection line.
Conclusions:
- The specific pattern of viral infection, characterized by the loss of viral genetic segments, controls the developmental stage at which male-killing occurs.
- Viral RNA load transmitted from the female parent does not influence the timing of male death.
- A shorter larval stage in the triple-infection line may enhance viral transmission efficiency compared to the double-infection line.
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