Herbivory and wounding upregulate a large suite of defense genes in hybrid poplar leaves. A strongly wound- and herbivore-induced gene with high similarity to Arabidopsis vegetative storage proteins (VSPs) and acid phosphatase (AP) was identified among genes strongly expressed during the poplar herbivore defense response. Phylogenetic analysis showed that the putative poplar acid phosphatase (PtdAP1) gene is part of an eight-member AP gene family in poplar, and is most closely related to a functionally characterized soybean nodule AP. Unlike the other poplar APs, PtdAP1 is expressed in variety of tissues, as observed in an analysis of EST data. Following wounding, the gene shows an expression profile similar to other known poplar defense genes such as protease inhibitors, chitinase, and polyphenol oxidase. Significantly, we show for the first time that subsequent to the wound-induction of PtdAP1 transcripts, AP protein and activity increase in extracts of leaves and other tissues. Although its mechanism of action is as yet unknown, these results suggest in hybrid poplar PtdAP1 is likely a component of the defense response against leaf-eating herbivores.
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