show Abstracthide AbstractPedunculate oak, Quercus robur is an abundant forest tree species that hosts a large and diverse consortium of beneficial ectomycorrhizal fungi (EMF), whereby EM formation is stimulated by mycorrhization helper bacteria such as Streptomyces sp. AcH 505. Oaks typically grow rhythmically, with alternating root flushes (RFs) and shoot flushes (SFs). We explored the poorly understood mechanisms by which oaks integrate signals induced by their beneficial microbes and endogenous rhythmic growth at the level of gene expression. To this end, we compared transcript profiles of oak microcuttings at RF and SF during interactions with AcH 505 alone and in combination with the basidiomycetous EMF Piloderma croceum. This work was part of the research program TrophinOak (www.trophinoak.de) of seven research groups working with oak microcuttings to study gene expression and resource allocation in multitrophic interactions, funded by the DFG, German Research Foundation.