Kinetics of Accumulation of the Three Non-structural Proteins of Alfalfa Mosaic Virus in Tobacco Plants

Abstract

Antisera to synthetic peptides corresponding to the C-termini of two non-structural proteins (NSP) of alfalfa mosaic virus (A1MV), P1 (126K) and P3 (32K), were prepared and characterized. These antisera, together with one which had previously been made against the C-terminus of P2 (90K), enabled us to detect the three NSPs in a crude membrane fraction from A1MV-infected tobacco leaves. The accumulation of these proteins at 25.degree. C and at 10.degree. C was followed as a function of time after inoculation, and their amounts were compared with viral replicase activity. All three proteins accumulated at the beginning of the infection period and then disappeared, P3 more rapidly than the other two. There was a good correlation between replicase activity and the amounts of P1 and P2, but not the amount of P3. These results are consistent with the notion that P1 and P2 are part f the replication complex. Although much less coat protein was made in inoculated leaves at 10.degree. C than at 25.degree. C, the maximum amounts of the three NSPs and the maximum replicase activity were at least as high at 10.degree. C as at 25.degree. C. Thus, 10.degree. C is not a restrictive temperature for the assembly of a functional replication complex.