CDNA sequence of the pepper severe mosaic virus coat protein gene.

Abstract

PeSMV was originally isolated in Argentina from diseased Capsicum annuum plants and classed as a possible member of the potyvirus group on the basis of morphological, biological, and immunological evidence (Feldman and Gracia, 1977). Although information concerning its economic significance is still imprecise, the virus is present in most pepperproducing areas and yields are drastically reduced in chronically infected plants. As part of a project to obtain resistant transgenic plants by means of coat protein-mediated protection, we cloned the PeSMV gRNA and obtained a partia1 nucleotide sequence of the PeSMV genome including the 3’ end of the replicase gene, the complete CP gene, and the 3’ noncoding region (Table I). PeSMV gRNA from strain 5-163 was used for cDNA synthesis. Clones located in the genome 3‘ end were identified by low-stringency hybridization with a radioactive PVY CP probe and dideoxy sequenced. A sequence spanning 1329 nucleotides from the 3‘ end was obtained, the first 998 encoding a continuous open reading frame. Comparison of the sequence encoding the putative PeSMV CP with that of PVY revealed a similarity of 71.6%. The 3’ noncoding sequences are different lengths (PeSMV, 471 nucleotides; PVY, 331 nucleotides) and were not directly comparable. The translated amino acid sequence corresponding to the putative PeSMV CP showed similarities of 80.9 and 62.1% with the PVY (Bravo-Almonacid and Mentaberry, 1989) and tobacco etch virus (Allison et al., 1985) CPs, respectively. Most of the sequence changes are clustered at the N-terminal region. The PeSMV sequence contains two additional codons between nucleotides 142 and 147 of the PVY CP sequence. On the other hand, severa1 sequence motifs strongly conserved in most potyvirus are present in the C-terminal threequarters of the sequence. Remarkably, the PeSMV sequence does not contain the amino acid motif DAG that was associated with aphid transmissibility (Atreya et al., 1991). This fact agrees with previous data showing that PeSMV is not aphid transmitted (Feldman and Gracia, 1977).