Biphasic Temporal and Spatial Induction Patterns of Defense-Related mRNAs and Proteins in Fungus-Infected Parsley Leaves.

Previous experiments using in situ RNA hybridization have shown that the mRNAs encoding phenylalanine ammonia-lyase, 4-coumarate:coenzyme A ligase, and pathogenesis-related protein 1 accumulated transiently around fungal infection sites in parsley (Petroselinum crispum) leaf buds. These studies have now been extended by (a) analyzing different stages of the infection process and (b) monitoring the timing of appearance and the spatial distribution of the proteins as well as the corresponding mRNAs. An early and short period of mRNA induction throughout a large portion of the infected leaf was followed by a longer period, during which the mRNA levels remained high in a more localized area around the site of fungal penetration with sharp borders toward the surrounding tissue. This biphasic pattern of mRNA accumulation was followed after some delay by the same pattern of protein accumulation.