Molecular analysis of poplar defense against herbivory: comparison of wound‐ and insect elicitor‐induced gene expression

Summary•  In order to characterize defense responses of hybrid poplar ( Populus trichocarpa ×  P. deltoides ), we profiled leaf transcript patterns elicited by wounding and by regurgitant from forest tent caterpillar (FTC; Malacosoma disstria ), a Lepidopteran defoliator of poplars. •  Macroarrays were used to compare transcript profiles. Both FTC‐regurgitant (FTC‐R) and mechanical wounding with pliers elicited expression of a variety of genes, and for these genes our analysis indicated that these treatments induced qualitatively similar responses. •  Similarily, a comparison of responses of directly treated and systemically induced leaves indicated extensive overlap in the sets of induced genes. FTC‐R was found to contain the insect‐derived elicitor volicitin. •  The simulated herbivory treatments resulted in the induction of genes involved in poplar defense and secondary metabolism. We also identified wound‐responsive genes with roles in primary metabolism, including a putative invertase, lipase, and acyl‐activating enzyme; some of these genes may have roles in defense signaling. In addition, we found three unknown genes containing a ZIM motif which may represent novel transcription factors.