Site-directed mutations in the potyvirus HC-PRO gene affect helper component activity, virus accumulation, and symptom expression in infected tobacco plants

Nucleic acid-binding properties of a bacterially expressed potato virus Y helper component-proteinase

“…Experimental evidence suggests a role for the N-terminal domain of HC-Pro in genome amplification (Atreya et al, 1992;Atreya & Pirone, 1993;Dolja et al, 1993) and the RNA-binding activity demonstrated here is consistent with this possibility. Although it is difficult to explain how a sequence non-specific protein such as HC-Pro could participate in regulation of virus replication, this could be modulated by association of HC-Pro with another (host or virus) protein to specifically recognize the virus RNA, or by a special compartmentalization process.…”

“…It shares 93 % and 91% (at the nucleotide level) and 96 % and 95% (at the amino acid level) identity with the corresponding sequence of potato virus C (Thornbury et al, 1990) and PVY Fr (Robaglia et al, 1989), respectively. The presence of a lysine at position 50, a residue shown to be important in HC-Pro-mediated aphid transmission of potyviruses (Atreya et al, 1992;Atreya & Pirone, 1993), is in agreement with the aphidtransmissible phenotype of this virus (K. Grbrr-S~lassi~, personal communication). No amino acid alterations were observed in regions known to be highly conserved between potyviruses (Granier et al, 1993), except the central CCC box described by Cronin et al (1995) which was CSC in PVY LYE84.…”

“…It has a well-characterized C-terminal papain-like proteolytic domain responsible for the release of its own C terminus from the polyprotein (Carrington et al, 1989 a). The N-terminal portion of HC-Pro is required for aphidmediated plant-to-plant transmission (Atreya et al, 1992;Atreya & Pirone, 1993). However, in a recent report a point mutation within the conserved C-terminal proline-threonine-lysine (PTK) box of HC-Pro was shown to be associated with loss of aphid transmissibility of zucchini yellow mosaic potyvirus (Granier et al, 1993;Huet et al, 1994), suggesting that more than one site in HC-Pro could be involved in aphid transmission activity.…”

“…Natural or site-directed mutations within this region not only abolished aphid transmissibility of the virus but were also associated with attenuated virulence and symptom expression in infected plants (Atreya et al, 1992;Atreya & Pirone, 1993;Dolja et al, 1993). These data strongly suggest a role for the N-terminal domain of HC-Pro in potyvirus genome amplification.…”

Loss of potyvirus transmissibility and helper-component activity correlate with non-retention of virions in aphid stylets

“…Mutations in either the coat protein or the helper component protein can result in loss of aphid transmissibility of a potyvirus (Atreya et al, 1990(Atreya et al, , 1991(Atreya et al, , 1992a.…”