Endosymbiotic bacteria associated with circulative transmission of potato leafroll virus by Myzus persicae

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 antibiotictreated 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.

Bacterial symbionts in insects or the story of communities affecting communities

“…In aphids and whiteflies, GroEL homologues are circulating in the haemolymph outside the bacterial cells [58]. It has been shown that virions bind to these GroEL homologues, thereby escaping destruction by the vector's immune system and allowing virus transmission [58,59]. It is not always clear whether GroEL of facultative or primary symbionts is involved in this process, and therefore it is unknown how much variability there is within the vector species.…”

“…GroEL is a protein produced by bacteria. In aphids and whiteflies, GroEL homologues are circulating in the haemolymph outside the bacterial cells [58]. It has been shown that virions bind to these GroEL homologues, thereby escaping destruction by the vector's immune system and allowing virus transmission [58,59].…”

Effects of Point Mutations in the Readthrough Domain of the Beet Western Yellows Virus Minor Capsid Protein on Virus Accumulation In Planta and on Transmission by Aphids

“…Interactions between the virus capsid and aphid components at all of these sites may be important in conferring vector specificity (12,14). Finally, in the hemocoel, binding of the virus to symbionin, a chaperonin secreted into the hemolymph by endosymbiotic bacteria of the aphid, is known to stabilize luteoviruses in a vector-nonspecific manner (9,32,33).…”

“…5A). For brevity, we shall refer to the wild-type sequence PVT (32)(33)(34) to which these mutations map as the PVT patch.…”

Detection of Coat Protein Gene of the Potato Leafroll Virus by Reverse Transcription Loop-Mediated Isothermal Amplification

“…Viruses of the family Luteoviridae belongs to ssRNA plant viruses, divided into three genera: Enamovirus, Luteovirus and Polerovirus [5]. Members of this family infect a broad range of mono-and dicotyledonous plants that they exclusively replicate in the phloem tissue [6]. PLRV infects potato plants, causing economic losses on the yield [7,8].…”