Detection of the 3a Protein of Cucumber Mosaic Virus in a Cell Wall Fraction from Infected Nicotiana clevelandii Plants

The 3a protein of cucumber mosaic virus was expressed in Escherichia coli and, after purification, used to produce an antiserum. The 3a protein was detected in a cell wall fraction obtained from infected Nicotiana clevelandii leaf tissue by immunoblotting using the 3a antiserum. The 3a protein reached a maximum level 4 days after inoculation and remained at this level for a further 8 days before slowly declining. In contrast, the virus capsid protein, detected in an 80 000 g pellet byimmunoblotting using a virus particle antiserum, reached a maximum 5 days after inoculation and remained at this level for at least a further 16 days.