The readthrough domain of pea enation mosaic virus coat protein is not essential for virus stability in the hemolymph of the pea aphid

Abstract

A fraction of the coat protein (CP) subunits in virions of members of the family Luteoviridae contain a C-terminal extension called the readthrough domain (RTD). The RTD is necessary for persistent aphid transmission, but its role is unknown. It has been reported to be required for virion stability in the hemolymph. Here, we tested whether this was the case for pea enation mosaic virus (PEMV) virions in the pea aphid (Acyrthosiphon pisum) using RNA1Delta, a natural deletion mutant lacking the middle portion of the RTD ORF, and CPDeltaRTD, in which the entire RTD ORF was deleted. In infected plants, RNA1Delta virions were as abundant and stable as wild-type (WT) virions, while CPDeltaRTD virions were unstable. No RTD of any size was translated from artificial subgenomic mRNA of CPDeltaRTD or RNA1Delta in vitro. Thus, only the major CP was present in the mutant virions. Using real-time RT-PCR to detect virion RNA, no significant differences in the concentration or stability of WT and RNA1Delta virions were detected in the aphid hemolymph at much longer times than are necessary for virus transmission. Thus, the RTD is not necessary for stability of PEMV RNA in the aphid hemolymph, and it must play another role in aphid transmission.

Role of Pea Enation Mosaic Virus Coat Protein in the Host Plant and Aphid Vector

“…This minor protein was described as involved in luteovirus transmission [50,51,52,53,54,55]. Although the readthrough domain of PEMV (33 kDa protein) is not essential for virus stability into the vector, it can indeed affect the transmission [32]. All the CP mutants in this study were able to express as a translational readthrough (RT) fusion with the 21 kDa CP detectable by western blot [16].…”

“…PEMV virions were partially purified from plants according Liu et al [32]. Briefly, individual infected pea plants were harvested at 15 and 21 dpi.…”

Arsenophonus GroEL Interacts with CLCuV and Is Localized in Midgut and Salivary Gland of Whitefly B. tabaci

“…However, recent studies using Monoclonal antibody (MAb) raised against Buchnera specific GroEL epitopes, reveal that Buchnera GroEL is not present in organs, other than the bacteriocytes, like haemolymph, gut and fat body, questioning the possible role played by Buchnera GroEL as a receptor to the luteovirus coat protein [27]. Another recent study on aphid-leutovirus interaction disproved the earlier hypothesis that the read through domain (RTD) of the virus is essential for persistent and circulative transmission by the aphid [53].…”

Editorial overview: Parasites/Parasitoids/Biological Control: Virus-insect interactions: progress and pitfalls

“…This work has now been extended to other plant virus-insect vector systems including begomovirus transmission by whitefly. In 2009, Liu et al, showed that the stability of a luteovirus mutant lacking the readthrough domain proposed to bind to GroEL in the hemolymph was no different from the stability of the wild type virus [7]. In 2011, Bouvaine et al, demonstrated that the association of GroEL with a plant virus in the aphid vector was an artifact resulting from the method of hemolymph collection.…”