Megumi Fukuda

Initiation site for assembly of several strains of TMV and its relation to occurrence of the short particles in infected plants

Abstract The site of initiation of rod assembly for a tomato (T) and a cowpea (Cc) strain of tobacco mosaic virus and for cucumber green mottle mosaic virus (CGMMV) was determined by electron microscopic serology. The initiation site on T-RNA was located at the same position as that of a common strain previously studied, being about 800 nucleotides away from the 3′-terminus. In contrast, the initiation site on Cc-RNA and CGMMV-RNA was found to be much closer to the 3′-terminus, only about 320 nucleotides away from the terminus, and hence within the coat protein cistron. The location of the initiation site of Cc and CGMMV explained why the coat protein messenger RNA of these strains, but not that of the common and the T strains, is encapsidated to form short particles.

Infectivity of partially encapsidated tobacco mosaic virus RNA.

Tobacco mosaic virus was reconstituted in vitro, and the infectivity of intermediate products at various stages of reconstitution was investigated in relation to their rod length. The infectivity of intermediates was exponentially related to their rod length throughout the reconstitution process, indicating that no particular region of TMV-RNA is preferentially susceptible to inactivation or more important for infection.