Priming the chromatin in response to heat stress in Arabidopsis thaliana – The role of Mediator in transcriptional memory

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Moderate heat stress (HS) primes a plant to subsequently withstand high temperatures that are lethal to a plant in the naïve state. After returning to non-stress temperatures the primed state is maintained over several days, and this memory is genetically separable from thermopriming. The underlying mechanism of HS memory, i. e. the maintenance of the primed state after HS, is not well understood. This project addresses the role of chromatin and transcriptional regulation in HS memory. Previously, we found that HS memory is associated with two types of transcriptional memory, sustained induction (type I) and enhanced re-induction upon recurring HS (type II). From a modifier screen for type II transcriptional memory we have identified several mutants that implicate the Mediator co-activator complex in HS-induced transcriptional memory. Mediator is a highly conserved multi-subunit co-activator complex that bridges signalling from gene-specific transcription factors to RNA polymerase II and the general transcriptional machinery. In this research project, we will study the mechanistic basis of Mediator in HS-induced transcriptional memory using genome-wide transcription and epigenomic profiling as well as protein interaction studies. Beyond insights into the mechanism of HS-induced transcriptional memory, the findings of this research project will have wider implications for our knowledge of Mediator function in plant-environment interactions and may ultimately provide new avenues for improving HS resilience in crop plants.