Molecular basis of plant viral virulence; the complete nucleotide sequence of an attenuated strain of tobacco mosaic virus

Abstract

The total genome sequence of L11A, an attenuated strain of tobacco mosaic virus (TMV), has been determined. This strain is able to multiply in tomato plants without inducing any remarkable symptoms, but to protect them from later infection with virulent TMV strains. When compared with the recently published total genome sequence of TMV L (the virulent ancestral strain of L11A) ten base substitutions were found in the L11A genome. Seven of these occurred in the third letters of in-phase codons and did not influence amino acids. Only three, which were in the common reading frame for both the 130K and 180K proteins, resulted in amino acid changes. Together with the result of the partial sequence of RNA of L11, an intermediate strain in sequential isolation from L to L11A, it is observed that one base at the nucleotide position 1117 is changed from L to L11 and two bases at the positions 2349 and 2754 are changed from L11 to L A11.

Nucleotide Sequence of the Genomic RNA of Pepper Mild Mottle Virus, a Resistance-breaking Tobamovirus in Pepper

“…It remains to be determined whether the attenuated biological behaviour of PMMV-S in tobacco, in comparison with TMV and ToMV, could be ascribed to regions of maximum sequence heterogeneity or to segments of the non-highly conserved sequence of the 126K/183K protein, as previously described for the attenuated L11A strain ofToMV (Nishiguchi et al, 1985) in which the amino acid substitutions responsible for this characteristic have been mapped in regions, not highly conserved, of the 126K protein (amino acid residues 348, 759 and 894). It is also unknown whether the ability of PMMV-S to break the resistance against tobamoviruses conferred by the E 1 and L 2 genes in pepper (Boukema et al, 1980;Garcia-Luque et al, 1990) is due to any of the amino acid changes which take place in this protein, as described for the Ltal strain of ToMV, in which two amino acid substitutions (Glu to Gin and Tyr to His) at positions 979 and 984, respectively (980 and 985 in the PMMV-S protein) have been identified as those responsible for the ability of this strain to break the Tm-l resistance gene in tomato .…”

Fluctuations of Particles on Chloroplast Thylakoid Membranes in Tomato Plants Infected with Virulent or Attenuated Strain of Tobacco Mosaic Virus.

“…L11A has been extensively studied at the molecular level10, 16,21). Since L11A shows interfering activity against the virulent strain TMV-L, L11A is being used providing commercially to protect tomato plants from TMV-L infection.…”

Attenuated plant viruses: preventing virus diseases and understanding the molecular mechanism

“…1a). In L 11 A, 11 base substitutions were located in the genome when compared with the wild-type, severe strain L (Nishiguchi et al 1985). Of those, only three at amino acid (aa) positions 348, 760 and 896 in the 130-kDa protein caused amino acid replacements.…”

“…These three amino acid replacements were compared with those in L 11 , from which L 11 A was derived (Goto and Nemoto 1971). Only one of them, the change from cysteine (C) in wild-type strains to tyrosine (Y) in attenuated strains at aa position 348 (at nucleotide position 1117), was conserved within these two attenuated virus strains (L 11 A and L 11 ), suggesting that the amino acid replacement at aa position 348 is important for virus attenuation (Nishiguchi et al 1985). Kubota et al (2003) later proved that the change of C-Y at aa position 348 in the infectious L cDNA clone rendered the mosaic symptom into an attenuated phenotype.…”