Description and Complementation Analysis of 13 Temperaturesensitive Mutants of Alfalfa Mosaic Virus

Abstract

Thirteen thermosensitive (ts) mutants of alfalfa mosaic virus (AMV), a virus with a tripartite genome, are described. Eight of these mutants were spontaneous, one was induced with HNO₂ and four were induced by u.v. irradiation of one purified component. Using supplementation tests six ts mutations were located on top component b (Tb), three on middle component (M) and four on bottom component (B). Complementation tests with mutants with ts defects on the same component showed that none of the ts mutants on Tb could complement each other; the three ts mutants on M could be subdivided into two complementation groups, while only one pair of mutants showed complementation from the four ts mutants on B. It was demonstrated that the coat proteins from the six ts mutants on Tb were not able to activate the AMV genome at 30 °C in tobacco.