Alfalfa mosaic virus temperature-sensitive mutants. III. Mutants with a putative defect in cell-to-cell transport

Forty-five mutants of alfalfa mosaic virus with a temperature-sensitive (ts) replication in tobacco leaf discs were assayed in cowpea protoplasts at 25 and 30 degrees . The extent of replication of 9 mutants at 30 degrees was less than 10% of that at 25 degrees, whereas the replication of 14 mutants was not affected at 30 degrees. Twenty-two mutants showed an intermediate ts behavior. Several mutants with a non-ts phenotype in cowpea protoplasts were also found to be non-ts in their replication in tobacco protoplasts. The observation that at 30 degrees these mutants are able to replicate in single cells but not in leaf discs suggests that they may be defective in a transportation function.