In vitro and in vivo translation of the ribonucleic acids of a cowpea strain of tobacco mosaic virus1

Experiments reported here support the notion that intact TMV RNA has genes which are not translated directly and that specific fragments of the RNA are the functional messengers for those genes.A discrete class of short nucleoprotein rods, in addition to the expected 300-nm rods, was observed by Morris in a cowpea strain of TMV isolated from infected cowpea tissue. We have found a third class of rods of intermediate length. RNAs from the three kinds of rods were separately translated in a wheat germ cell-free protein synthesis system. RNA from the short rods directed the synthesis of a polypeptide with some properties of capsid protein: the same electrophoretic mobility in detergent-impregnated polyacrylamide gels and the ability to participate in a reconstitution reaction with virus RNA. RNA from long rods directed the synthesis of a spectrum of polypeptides. Among these one of ～130,000 molecular weight predominated. It had the same electrophoretic mobility as a polypeptide which was recovered from virus-infected tissue, but not from mock-inoculated tissue. RNA from rods of an intermediate length class directed the synthesis of one or two polypeptides with apparent molecular weights of about 30,000. Capsid polypeptide could not be demonstrated among the products formed under the direction of the long or immediate rods RNAs. However, RNA-RNA hybridization experiments indicate that short and intermediate rod RNAs share nucleotide sequences with each other and with the long rod RNA. The possible relationships of these results to the replication of the common strain of TMV and brome mosaic virus are discussed.