Potyvirus aphid transmission requires helper component and homologous coat protein for maximal efficiency

Abstract

Aphid transmission of potyviruses depends on the presence of specific sequence domains in two virus encoded proteins, the coat protein (CP) and helper component-proteinase (HC-Pro). Aphid transmissable peanut stripe virus (PStV), like most potyviruses, has an Asp-Ala-Gly (DAG) motif in the amino-terminal part of the CP. Peanut Mottle Virus (PeMoV) was determined to be highly aphid transmissible but has a unique Asp-Ala-Ala-Ala (DAAA) motif. To determine if the DAAA motif could functionally replace the DAG motif in PStV, mutations were made in a full-length cDNA clone of PStV. All of the mutations in the CP DAG motif abolished aphid transmissibility of PStV but did not affect virus infectivity. The aphid transmissibility of the PStV-DAAA mutant was partially restored by feeding aphids an artificial diet containing purified virus and PeMoV HC-Pro. The PStV-DAAA virus was poorly transmitted by aphids in vitro with HC-Pro purified from PStV or tobacco vein mottling virus (TVMV) infected plants. These experiments support the theory that specific HC-Pro/CP interactions are required for efficient aphid transmission. Based upon the sequence comparisons of 16 potyviral HC-Pro proteins several conserved motifs and striking differences have been identified. PeMoV was determined to have an Ala-Ser-Cys (ASC) HC-Pro motif instead of a highly conserved Cys-Cys-Cys (CCC) motif. We have predicted that this CCC motif could play an important role in the specific interaction between the HC-Pro and the CP DAG motif.

Sharka: The Past, The Present and The Future

“…The role of CP and its binding with the helper component (HC) in aphid transmission is demonstrated [144,145,146]. CP-HC interactions are highly specific and require a Cys-Cys-Cys motif for specific interaction with CP Asp-Ala-Gly (DAG) motif [147]. Changes in DAG motif are the cause of systemic infection failure, but they do not affect replication and production of virions [148,149].…”

Recombination and selection pressure in the ipomovirus sweet potato mild mottle virus (Potyviridae) in wild species and cultivated sweetpotato in the centre of evolution in East Africa

“…The KITC, KLSC or RITC motifs are also critical for potyvirus retention in the aphid stylets (Blanc et al, 1998) and a KACC, KTCC or RTCC motif was found at the corresponding position in SPMMV HC-Pro. Previously, a highly aphid-transmissible potyvirus, peanut mottle virus, was found to possess a KVSC motif instead of KITC in the HC-Pro and a unique DAA motif instead of DAG in the CP N terminus (Flasinski & Cassidy, 1998). Hence, identification of vectors for SPMMV will provide an interesting subject for study.…”

Algerian watermelon mosaic virus (AWMV): a new potyvirus species in the PRSV cluster

“…The PTR motif was also observed in MWMV isolates from Morocco, South Africa, Cameroon and Tunisia [8]. The serine in the second position in CSC motif is also present in a few potyviruses including PRSV-W [21] and MWMV [8]. H4 isolate was found previously to be readily transmissible by aphids in a non-persistent manner [9], thus indicating that the PTR motif in this context does not abolish aphid transmissibility.…”