Sequence comparison of the HC-Pro and CP proteins of twoPotato virus Ystrains differing in aphid transmission and systemic movement

Abstract

Nucleotide and amino acid sequences of the helper component protease (HC-Pro) and the coat protein (CP) of two Hungarian Potato virus Y (PVY) isolates, differing in aphid transmissibility were determined. Isolate PVY-5 belongs to the common “O” strain (PVY O ), whereas isolates PVY-98 and PVY-111 belong to the “N” (PVY N ) and the PVY-NTN and PVY-H to the “NTN” (PVY NTN ) strains, respectively. The PVY-5 isolate varied significantly from the others in aphid transmission and in the ability to systemically infect potato plants. To elucidate whether these differences were due to mutations affecting known functional motifs, the corresponding cistrons of the two proteins were sequenced and aligned. Our analysis showed that none of the well-known motifs, responsible for aphid transmission in the two proteins had been affected. However, the defective isolate had two natural mutations in the HC-Pro in the vicinity of the PTK motif, and a number of mutations in the CP, distributed both in the N-terminus and the central region. As these two proteins are the only known viral participants in the aphid transmission mechanism, it is likely that some of the observed mutations might be involved in this process. Thus, our results indicate that other, previously unidentified sequences or factors may influence virus-vector interactions and transmission of PVY.