Virus Transmission Mechanisms in Vectors

______ account for the transmission of 50% of the insect-vectored viruses

______ are exquisitely designed for their roles as vector. Piercing–sucking mouthparts facilitate the delivery of virions into plant cells without causing irrevocable damage

______ are globally distributed and there are more than 200 vector species identified, a number that is most likely a gross underestimate

Most plant ______ are the result of a coevolution of virus and vector

The CP translational readthrough protein binds symbionin, a protein homologue of the Escherichia coli chaperonin GroEL that is produced by the ______ endosymbiotic bacteria Buchnera spp. and released into the haemolymph

Umbraviruses are mechanically transmissible, but their genomes do not encode a CP and they are aphid-nontransmissible. They achieve aphid transmission competence by associating with luteoviruses in plants dually infected by both viruses

The circulative propagative plant viruses bear a striking resemblance to animal viruses transmitted by ______. In both cases, viruses replicate in the insect vector and exit via the salivary glands

Aphid vectors are responsible for positioning viruses at their sites of infection. Because salivation appears to play an essential role in the release of virions, an understanding of virus entry may ultimately require a better understanding of salivation

______, genus Potyvirus, contains the most potyviruses (definitive and tentative) among aphid-transmitted plant viruses, with many species having narrow host ranges

Aphids primarily belong to the subfamily ______, and are responsible for the transmission of most plant viruses through a polyphagous feeding habit, parthenogenetic reproduction, and needle-like stylet

Feeding behavior and host plant selection of ______ can influence their potential as virus vectors

______ play a crucial role in the spread and control of viral plant diseases, making understanding their transmission essential for epidemiology.

Noncirculative viruses are primarily associated with the aphid's ______

Circulative viruses can be nonpropagative or circulative ______, depending on whether they replicate within the vector.

The majority of aphid-vectored plant viruses are transmitted ______ and can be classified as nonpersistent or semipersistent.

Potato virus Y and other potyviruses require the helper component (HC) protein for ______, which acts as a bridge to mediate virion binding in the aphid's stylet.

Semipersistent transmission lies in the ______ period of hours to days. The best characterized of the semipersistent, aphid-transmitted viruses are the caulimoviruses and the closteroviruses. Cauliflower mosaic virus, the type member of the genus Caulimovirus, has adopted a helper-dependent transmission strategy, but with the added twist of requiring two viral-encoded, nonstructural proteins, P2 and P3

Helper-dependent transmission strategy, but with the added twist of requiring two viral-encoded, nonstructural proteins, P2 and P3 (Blanc et al., 2001). A P2–P3–______ complex is formed, with P2 thought to mediate binding in the aphid whereas P3 binds to s; the ‘bridge’ would be formed via P2–P3 interactions (Drucker et al., 2002; Leh et al., 1999, 2001). Intriguingly, aphids may first acquire P2 from infected mesophyll cells, and P3– complexes can subsequently be taken up from other mesophyll or phloem cells (Drucker et al., 2002; Palacios et al., 2002).

Because HC and virus particles can be acquired sequentially, it is possible for one virus to assist in the ______ of a second virus. This phenomenon, termed HC-transcomplementation, has been observed in a number of families of plant viruses and can influence the epidemiology and spread of plant viruses (Froissart et al., 2002). Examples of semipersistent aphid ______ can be found in three other genera of plant viruses (Table 1). Among them, Parsnip yellow fleck virus (PYFV) (genus: Sequivirus) also employs a helper strategy in its ______.

Viruses belonging to the family ______ have particles that are composed of at least two forms of capsid proteins: the major CP and the minor CP (CPm). Although little is known about the determinants of aphid transmission for the viruses in this family, evidence from one member, the whitefly-transmitted Lettuce infectious yellows virus (genus: Crinivirus), indicates they are present on the CPm (Tian et al., 1999).