Epigenetic Regulation of Genome Function in Populus

Change is a constant in life, and being able to respond to change is essential for every living being. This may be especially true for sessile long-lived perennials with a complex life cycle like trees. In order to synchronize developmental decisions, growth, and performance with prevailing conditions, a precise interpretation of the given, usually static, genome is therefore of particular importance. Here, the epigenome, a fascinating, metastable layer of genome regulation, emerges as a central player. The epigenome integrates internal and external information into existing gene regulatory circuits allowing to shape development and tree responses to the environment. The epigenome comprises a set of modifications to DNA and its associated components that regulate genome function via chromatin modulation without changing the underlying DNA sequence. Epigenetic marks are not necessarily a temporary feature. They can be transmitted faithfully across cell divisions or even generations, thus retaining and passing on information. Here, we compile and integrate the gradually increasing body of knowledge on epigenome plasticity and epigenetic regulation in Populus. We focus on examples for epigenetic contributions to genome-encoded and environmentally modulated processes in development related to organ formation, growth regulation, and sex determination. Recent advances in technologies may spur further interest and hold promise for new insights into the exquisite epigenetic regulation of genome function in complex woody plants.