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Endosymbiotic bacteria associated with circulative transmission of potato leafroll virus by Myzus persicae
J F van den Heuvel1, M Verbeek, F van der Wilk
1DLO Research Institute for Plant Protection (IPO-DLO), Wageningen, The Netherlands.
Abstract:
In order to understand the molecular mechanisms underlying circulative transmission of potato leafroll virus (PLRV) by aphids, we screened Myzus persicae proteins as putative PLRV binding molecules using a virus overlay assay of protein blots. In this way, we found that purified PLRV particles exhibited affinity for five aphid proteins. The one most readily detected has an M(r) of 63K, and was identified as symbionin. This is the predominant protein synthesized by the bacterial endosymbiont of the aphid and is released into the haemolymph. Since further studies clearly showed that PLRV particles also bind to native symbionin, it was envisaged that virus particles when acquired into the haemocoel of an aphid interact with symbionin. Inhibition of prokaryotic protein synthesis by feeding M. persicae nymphs on an antibiotic-containing artificial diet prior to PLRV acquisition reduced virus transmission by more than 70%. The major coat protein of the virus was found to be degraded in the antibiotic-treated aphids; this would obviously have resulted in an increased exposure of viral RNA to enzymic breakdown and concomitant loss of infectivity. For these reasons we conclude that endosymbiotic bacteria play a crucial role in determining the persistent nature of PLRV in the aphid haemolymph and that symbionin is probably the key protein in this interaction.
Insights
Aphid endosymbiotic bacteria are crucial for potato leafroll virus (PLRV) transmission. The bacterial protein symbionin binds PLRV, protecting it from degradation within the aphid, ensuring persistent virus circulation.
Area of Science:
- Plant Virology
- Insect-Microbe Interactions
- Molecular Entomology
Background:
- Potato leafroll virus (PLRV) is transmitted by aphids, but the molecular mechanisms are not fully understood.
- Understanding aphid-virus interactions is key to controlling persistent virus transmission.
Purpose of the Study:
- To identify aphid proteins involved in PLRV binding and circulative transmission.
- To elucidate the role of bacterial endosymbionts in PLRV persistence within the aphid vector.
Main Methods:
- Virus overlay assay of Myzus persicae protein blots to screen for PLRV binding proteins.
- Identification of binding proteins using molecular weight and further characterization.
- Inhibition of bacterial protein synthesis using antibiotics to assess impact on virus transmission.
Main Results:
- Five Myzus persicae proteins bound purified PLRV particles, with symbionin (63K M(r)) showing the strongest affinity.
- PLRV particles bound to native symbionin, suggesting interaction in the aphid haemolymph.
- Antibiotic treatment inhibiting symbionin synthesis reduced PLRV transmission by over 70% and led to viral coat protein degradation.
Conclusions:
- Bacterial endosymbionts, specifically through the protein symbionin, play a critical role in the persistent transmission of PLRV.
- Symbionin likely protects PLRV particles from degradation in the aphid haemolymph, maintaining virus infectivity.