- Volume 64, Issue 5, 1983

Analysis of differentially radiolabelled avian infectious bronchitis virus (IBV) indicated that the matrix (M) polypeptides of mol. wt. 23 × 103 (23K), 26K, 28K, 30K and 34K (M23 to M34) which have been shown to give the same peptide maps, differed in their degree of glycosylation; M23 was not glycosylated while glycosylation increased with increasing mol. wt. from M26 to M34. Both glucosamine and mannose were components of M26 to M34 but [3H]fucose appeared to be associated mainly with M34. Endo-β-N-acetylglucosaminidase H removed oligosaccharides from M28 and M30 but not M26 and M34, to give a polypeptide of 23K. The surface projection glycopolypeptides S1 (90K) and S2 (84K) incorporated 3H-labelled glucosamine and mannose but not fucose and had oligosaccharides removed by endoglycosidase H. The mol. wt. of the resultant polypeptides varied among experiments; the lowest mol. wt. observed were 64K and 61K. These results indicate (i) that the polypeptide moieties of the S polypeptides are approximately 64K and 61K, and 23K for the M polypeptide, (ii) that the oligosaccharides of the S and M polypeptides are of the high-mannose type and are linked to the polypeptides by N-glycosidic linkages, and (iii) that the M glycoprotein of IBV differs from that of murine coronaviruses and bovine coronavirus L9 which have O-linked oligosaccharides.

The isometric particles of lucerne transient streak virus (LTSV) contain linear ssRNA of mol. wt. approx. 1.4 × 106 (RNA-1) and ssRNA of mol. wt. approx. 1.2 × 105 in both a linear and circular form (RNA-2). Unfractionated LTSV RNA induced necrotic local lesions in leaves of Chenopodium amaranticolor whereas RNA-1, partially separated from RNA-2 by gel electrophoresis, induced many chlorotic local lesions but few necrotic ones. Cultures obtained from either lesion type continued to induce only chlorotic (C isolate) or necrotic lesions (N isolate) on subsequent passage. Apart from the lesion type in Chenopodium species, the isolates were indistinguishable except that particles of isolate N contained both RNA-1 and RNA-2 whereas those of isolate C contained RNA-1 but no RNA-2; RNA-2 was also not detected in leaves inoculated with isolate C. RNA-2 alone did not infect C. amaranticolor but when it was added to inocula of RNA from isolate C, a proportion of the lesions induced were necrotic and this proportion increased with increasing concentration of RNA-2. The infectivity of RNA-1 was destroyed by treatment with snake venom phosphodiesterase or proteinase K but the ability of RNA-2 to alter the lesion type induced by isolate C was unaffected by these treatments, suggesting that the molecules of RNA-2 are biologically functional and do not need a genome-linked protein for this activity. These results suggest that RNA-2 found in particles of LTSV is not part of the virus genome but may be a satellite RNA that affects symptom expression.