Hydroxyacetophenone defenses in white spruce against spruce budworm

<b>Abstract</b><br/><p>We review a recently discovered <span class="il">white</span> <span class="il">spruce</span> (Picea glauca) chemical defense <span class="il">against</span> <span class="il">spruce</span> <span class="il">budworm</span> (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.</p>