Hydroxyacetophenone defenses in white spruce against spruce budworm

We review a recently discovered white spruce (Picea glauca) chemical
defense against spruce budworm (Choristoneura fumiferana) involving
hydroxyacetophenones. These defense metabolites detected in the foliage
accumulate variably as the aglycons, piceol and pungenol, or the
corresponding glucosides, picein and pungenin. We summarize current
knowledge of the genomic, molecular and biochemical as well as genetic
underpinnings of this defense and its effects on C. fumiferana. We present
an update with new results on the ontogenic variation and the phenological
window of this defense, including analysis of transcript responses in P.
glauca to C. fumiferana herbivory. We also discuss this chemical defense
from an evolutionary and a breeding context.