Comparison of the in vitro Translation Products of Wild-type and a Deletion Mutant of Soil-borne Wheat Mosaic Virus

SummaryA wild-type isolate (WT) of soil-borne wheat mosaic virus (SBWMV, isolate JT) (RNA I 6·9 kb and RNA II 3·6 kb) was successively transferred to wheat plants by mechanical inoculation and a deletion mutant (DM) (RNA I 6·9 kb and RNA II 2·1 kb) was produced. In wheat germ extracts, RNA I of both WT and DM directed synthesis of polypeptides having mol. wt. of 220000 (220K) and 150K, and RNA II of both WT and DM directed synthesis of 25K and 19K polypeptides. Incubation in wheat germ extracts of WT or DM virions purified with an alkaline buffer also gave 220K, 25K and 19K polypeptides as major products and a 150K polypeptide as a minor product. In rabbit reticulocyte lysates, RNA I of both WT and DM directed synthesis of only the 220K polypeptide, whereas WT RNA II produced 100K, 46K, 25K and 19K polypeptides and DM RNA II, 31K, 25K and 19K polypeptides. SBWMV DM antiserum precipitated polypeptides of 100K, 31K, 25K and 19K but not 220K and 46K. The 19K polypeptide was identified as the capsid protein from its electrophoretic mobility and its reaction with antiserum to virus particles. Thus, the differences between the in vitro translation products of WT and DM SBWMV were confined only to those coded by RNA II.