This review describes the proposed mechanism(s) of classical virus cro
ss-protection in plants, followed by those suggested for coat protein-
mediated resistance (CP-mediated resistance). Although both have commo
n features, cross-protection is thought to be a complex response cause
d by the replication and expression of the entire viral genome, wherea
s the resistance conferred by the expression of a virus coat protein g
ene is more limited. The term genetically engineered cross-protection
is frequently used because in many cases the phenotype of resistance m
imics that of cross-protection. However, CP-mediated resistance, altho
ugh a narrow term, more accurately describes the resistance that resul
ts from the expression of a virus CP gene in transgenic plants.