The specific transmission of Grapevine fanleaf virus by its nematode vector Xiphinema index is solely determined by the viral coat protein

Abstract

The viral determinants involved in the specific transmission of Grapevine fanleaf virus (GFLV) by its nematode vector Xiphinema index are located within the 513 C-terminal residues of the RNA2-encoded polyprotein, that is, the 9 C-terminal amino acids of the movement protein (2BMP) and contiguous 504 amino acids of the coat protein (2CCP) [Virology 291 (2001) 161]. To further delineate the viral determinants responsible for the specific spread, the four amino acids that are different within the 9 C-terminal 2BMP residues between GFLV and Arabis mosaic virus (ArMV), another nepovirus which is transmitted by Xiphinema diversicaudatum but not by X. index, were subjected to mutational analysis. Of the recombinant viruses derived from transcripts of GFLV RNA1 and RNA2 mutants that systemically infected herbaceous host plants, all with the 2CCP of GFLV were transmitted by X. index unlike none with the 2CCP of ArMV, regardless of the mutations within the 2BMP C-terminus. These results demonstrate that the coat protein is the sole viral determinant for the specific spread of GFLV by X. index.

A Stretch of 11 Amino Acids in the βB-βC Loop of the Coat Protein of Grapevine Fanleaf Virus Is Essential for Transmission by the Nematode Xiphinema index

“…ArMV-S was the only virus transmitted by X. diversicaudatum (Table 2). Transmission rates varied between 67 and 100%, which is in complete agreement with previous reports on GFLV and ArMV transmission rates (4,5). Such differences were statistically not sufficient to indicate possible variations in transmission efficiency between transmitted isolates.…”

“…Previous studies showed that the specific transmission of GFLV and ArMV by X. index and X. diversicaudatum, respectively, is determined by their respective CPs (4,23). The identification of CP residues involved in transmission has been hampered by unsuccessful attempts at isolating natural GFLV or ArMV isolates that are deficient in nematode transmission and by a lack of resolved virion structure.…”

“…Synthetic GFLV, i.e., RNA derived from pMV13 and pVec Acc65I 2ABC, referred to as 2ABC, and wild-type ArMV-S were used as controls in transmission assays with X. index and X. diversicaudatum. The presence of GFLV and ArMV was assessed in leaves of source plants by DAS-ELISA (4,23).…”

“…The transmissibility of recombinant viruses that induced systemic plant infection, i.e., G1, AG1, and AG2, by X. index and X. diversicaudatum was evaluated (4,5). Recombinant AG2 was not transmitted by any of the two Xiphinema species, whereas…”

Bacteriophage Migration via Nematode Vectors: Host-Parasite-Consumer Interactions in Laboratory Microcosms

“…DNA virus examples include pea early-browning virus (41,42) and tobacco rattle virus (19,20); these tobraviruses are generally ingested by worms foraging on infected root cells, can reside in the worm pharyngeal lumen, and are either posteriorly released or evolved for anterior release (transmitted to a new host), depending on the nematode species (18,20). Grapevine fanleaf virus (family Comoviridae) is a segmented RNA virus that is similarly carried by a nematode vector, and it causes the most severe viral disease of grapevines worldwide, reducing fruit yields up to 80% (1,43).…”