Journal of General Virology, Vol 79, 2349-2358, Copyright © 1998 by Society for General Microbiology

ARTICLES

Nucleotide sequence, genetic organization and expression strategy of the double-stranded RNA associated with the '447' cytoplasmic male sterility trait in Vicia faba

P Pfeiffer
Institut de Biologie Moleculaire des Plantes du CNRS, Strasbourg, France.

The entire nucleotide sequence of the double-stranded (ds) RNA associated with the unconventional '447' cytoplasmic male sterility (CMS) trait in Vicia faba was determined from overlapping cDNA clones and by RT-PCR. Confirming previous observations, it was found that the negative-strand was continuous and 17,635 nt long, while the positive- strand featured an interruption, probably a nick, that could potentially define two subgenomic RNAs of 2735 nt and 14,900 nt, with the smaller RNA being located on the 5' side. The entire positive- strand could encode a single in-frame ORF starting at the first AUG at position 42-44 and ending with a TGA at 17,517-17,519. This long potential polypeptide with a predicted molecular mass of 654,109 is the largest described to date in the plant kingdom and contains conserved amino acid sequence motifs typical of viral helicases and RNA-dependent RNA polymerases (RDRP). Only limited sequence homology was detected with the ORF B encoded by the hypovirulence-associated dsRNA of chestnut blight fungus, a dsRNA replicon similarly contained in host- derived membranous vesicles and considered to share a common ancestry with potyviruses. By contrast, the helicase and RDRP domains were in the same respective arrangement and shared extensive sequence homologies with those identified in the polyprotein encoded by the dsRNA isolated from Japonica rice, another dsRNA replicon featuring a specific nick in the positive-strand. Although no proteolytic self- cleavage activity has yet been demonstrated, it appears likely that this long ORF is a polyprotein that undergoes proteolytic maturation, with one of the polypeptides derived by self-cleavage being the determinant of the CMS trait.

This article has been cited by other articles:

				C. V. Hacker, C. M. Brasier, and K. W. Buck A double-stranded RNA from a Phytophthora species is related to the plant endornaviruses and contains a putative UDP glycosyltransferase gene J. Gen. Virol., May 1, 2005; 86(5): 1561 - 1570. [Abstract] [Full Text] [PDF]

				J. A. Bruenn A structural and primary sequence comparison of the viral RNA-dependent RNA polymerases Nucleic Acids Res., April 1, 2003; 31(7): 1821 - 1829. [Abstract] [Full Text] [PDF]

				H. Horiuchi, T. Udagawa, R. Koga, H. Moriyama, and T. Fukuhara RNA-Dependent RNA Polymerase Activity Associated with Endogenous Double-Stranded RNA in Rice Plant Cell Physiol., February 1, 2001; 42(2): 197 - 203. [Abstract] [Full Text] [PDF]

				M. J. Gibbs, R. Koga, H. Moriyama, P. Pfeiffer, and T. Fukuhara Phylogenetic analysis of some large double-stranded RNA replicons from plants suggests they evolved from a defective single-stranded RNA virus J. Gen. Virol., January 1, 2000; 81(1): 227 - 233. [Abstract] [Full Text]

				H. Moriyama, H. Horiuchi, R. Koga, and T. Fukuhara Molecular Characterization of Two Endogenous Double-stranded RNAs in Rice and Their Inheritance by Interspecific Hybrids J. Biol. Chem., March 12, 1999; 274(11): 6882 - 6888. [Abstract] [Full Text] [PDF]