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Questions and Answers
True or false: Aphids are responsible for the transmission of 50% of insect-vectored viruses?
True
True or false: Aphids cause irrevocable damage to plant cells while delivering virions?
False
True or false: Aphid populations can increase at extraordinarily high rates due to sexual reproduction?
False
True or false: There are more than 200 identified aphid vector species, which is likely an overestimate?
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True or false: Most plant viruses are the result of a coevolution of virus and vector?
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Noncirculative viruses are primarily associated with the aphid's mouthparts and foregut.
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The majority of aphid-vectored plant viruses are transmitted noncirculatively.
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Nonpersistent transmission is characterized by long acquisition and inoculation times.
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Potato virus Y requires the helper component (HC) protein alone for transmission.
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Semipersistent transmission occurs when virions are retained in the vector for shorter periods.
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CP translational readthrough protein binds symbionin, a protein homologue of the Escherichia coli chaperonin GroEL that is produced by the aphid endosymbiotic bacteria Buchnera spp.
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Symbionin plays a role in vector specificity by binding luteoviruses of both vector and nonvector aphids
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Umbraviruses are mechanically transmissible and encode a CP for aphid transmission
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Circulative propagative plant viruses can be transmitted to offspring through a transovarial route in aphids
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Potyviridae contains the most potyviruses among aphid-transmitted plant viruses.
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Virus-encoded determinants for transmission have been identified in all plant rhabdoviruses
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Alfamovirus and Cucumovirus have many species with narrow host ranges.
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Aphids primarily belong to the subfamily Aphidinae.
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Feeding behavior and host plant selection of aphids do not influence their potential as virus vectors.
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Understanding aphid transmission is not essential for the epidemiology of viral plant diseases.
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Semipersistently transmitted viruses are only transmitted by aphids and not by other insects.
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Cauliflower mosaic virus (CaMV) employs a helper-dependent transmission strategy.
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Semipersistently transmitted viruses require longer acquisition and retention periods compared to circulatively transmitted viruses.
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Helper complementation (HC-transcomplementation) is not observed in families of plant viruses.
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The CP is the primary determinant of transmission for circulatively, nonpropagatively vectored viruses and plays a role in vector specificity.
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Study Notes
- Semipersistent viruses are transmitted through aphids, with acquisition occurring within minutes to hours, and the efficiency increasing with prolonged feeding.
- Cauliflower mosaic virus (CaMV) is a member of the genus Caulimovirus that employs a helper-dependent transmission strategy.
- CaMV requires two non-structural proteins, P2 and P3, for transmission. P2 and P3 form a complex, with P2 binding to the aphid and P3 binding to virions.
- Aphids may first acquire P2 from infected mesophyll cells and subsequently take up P3–virion complexes from other cells.
- P2 binds to microtubules in vivo, but the implications for transmission are not known.
- Helper complementation (HC-transcomplementation) is a phenomenon observed in some families of plant viruses, where one virus assists in the transmission of a second virus.
- Semipersistently transmitted viruses can be found in three other genera: Sequivirus (Parsnip yellow fleck virus), Waikavirus (Anthriscus yellows virus), and Closteroviridae (whitefly-transmitted Lettuce infectious yellows virus).
- Whiteflies and leafhoppers are additional insects that transmit semipersistently transmitted viruses.
- Circulatively transmitted viruses require longer acquisition and retention periods, attributed to their phloem-limited nature and extensive passage through the aphid.
- Circulatively transmitted viruses are either nonpropagative or propagative in the aphid.
- Aphids remain viruliferous for extended periods.
- Vector specificity, i.e., transmission by specific aphid species, is a prominent feature of circulatively transmitted viruses.
- The CP is the primary determinant of transmission for circulatively, nonpropagatively vectored viruses and plays a role in vector specificity.
- In Barley yellow dwarf virus (BYDV) and related luteoviruses, the CP determines vector specificity through a phenomenon known as transcapsidation and genomic masking.
- A second minor structural protein, a CP translational readthrough protein, is required for aphid transmission and may play a role in vector specificity for circulatively, nonpropagatively transmitted viruses.
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Description
Test your knowledge about the fundamental distinction of virus transmission mechanisms, including circulation and retention of virions within the vector. Explore how viruses are transported within the vector and ultimately exit the host.
