Quercus robur cultivar:DF159 Transcriptome or Gene expression. Quercus robur cultivar:DF159

Herbivores and mycorrhizal fungi interactively influence the growth, resource utilization, and herbivore defense of plants. We studied these interactions in a tri-trophic system comprising Quercus robur, the herbivore Lymantria dispar and the ectomycorrhizal fungus Piloderma croceum under controlled laboratory conditions at the levels of gene expression and carbon/nitrogen allocation. Taking advantage of the endogenous rhythmic growth displayed by oak, we thereby compared gene transcript abundances and resource shifts during shoot growth with those during the alternating root growth flushes. During root flush, herbivore feeding on oak leaves led to increased expression of genes related to plant growth and enriched GO terms related to cell wall, DNA replication, and defense. C/N-allocation analyses indicated an increased export of resources from aboveground plant parts to the roots. Accordingly the expression of genes related to the transport of carbohydrates increased upon herbivore attack in leaves at root flush. Inoculation with an ectomycorrhizal fungus attenuated these effects but instead caused an increased expression of genes related to the production of VOC’s. We conclude that oak defense gene expression response against herbivory is strong in root flush, but that this response is strongly inhibited by an ectomycorrhizal fungus and it is extremely weak at shoot flush