Coat Protein of Melon Necrotic Spot Carmovirus is More Similar to Those of Tombusviruses than Those of Carmoviruses

Abstract

SUMMARYComplementary DNA copies of the genomic RNA of melon necrotic spot virus (MNSV) have been cloned and the region deduced to encode the coat protein has been sequenced. The putative coat protein coding region, located near the 3' end of the genome, consists of 1170 nucleotides and has the potential to encode a 390 amino acid protein of Mr 41 840. Our data show that although MNSV is a carmovirus, its coat protein more closely resembles those of the tombusviruses than those of the carmoviruses sequenced to date, in both the extent of sequence similarity and in the length of the random/arm and protruding domains of the coat protein. Furthermore, dot matrix comparisons revealed sequence similarity between the coat protein protruding domains of MNSV and the cucumber necrosis tombusvirus.

Nucleotide sequence and genomic organization of melon necrotic spot virus

“…Purification of MNSV and virion RNA as well as synthesis and cloning of MNSV eDNA have been described (Riviere et al, 1989).…”

“…The ORFs encoding p14 and p7B terminate with an ochre codon. Overlapping the 3' ends of these ORFs by 11 nucleotides is an ORF in reading frame 1, which encodes the 41840 Mr coat protein (p42) which has been previously described (Riviere et al, 1989). The ochre terminator of the p42 ORF is followed by a Y-proximal non-coding region of at least 276 nucleotides.…”

“…The nucleotide sequence of the ORF encoding the coat protein of MNSV, and its deduced amino acid sequence have previously been described (Riviere et al, 1989). Detailed comparisons showed that although the MNSV coat protein shares a high degree of similarity with the coat proteins of both the carmo-and the tombusviruses, it resembles the coat proteins of tombusviruses more closely.…”

“…Nucleotide sequence data have shown that these two groups of viruses are closely related . Physicochemical properties which MNSV shares with these viruses include a small (about 30 nm) spherical particle (Hibi & Furuki, 1985) with a single type of capsid protein of about 42K (Bos et al, 1984;Riviere et al, 1989) and a monopartite, singlestranded (ss) RNA genome of Mr 1"5 × 106 (Hibi & Furuki, 1985).…”

“…Its deduced amino acid sequence shares significant sequence similarity with the coat proteins of both carmo-0000-9430 © 1990 SGM and tombusviruses. Detailed comparisons, however, reveal that although MNSV is a carmovirus, its coat protein resembles the coat proteins of tombusviruses more closely than those of other carmoviruses (Riviere et al, 1989). In this paper we report the nucleotide sequence of the MNSV genome and compare the organization and deduced amino acid sequences of its major open reading frames (ORFs) with those of other plant viruses.…”