My group at the John Innes Centre, Norwich, addresses how plants register seasonal temperature signals to time development. The floral repressor gene (FLC) is a major regulator of flowering timing in Arabidopsis and related plant species. Our genetic characterisation of silencing mechanisms regulating FLC has led us to study the conserved co-transcriptional processes modulating quantitative transcriptional output, and Polycomb epigenetic switches. Natural temperature fluctuations act at multiple levels within both mechanisms.
The co-transcription-coupled silencing mechanism links transcription termination to changes in the local chromatin environment. Our recent collaboration with Lori Passmore’s group showed that this occurs through the CPF phosphatase module of the RNA 3’ processing machinery physically associating with a chromatin modifier complex. Termination of antisense transcripts, called COOLAIR, at FLC results in reduced histone methylation locally, lowering RNA Pol II processivity on both strands during subsequent rounds of transcription. This promotes nucleation of Polycomb silencing in FLC and the switch from an epigenetically on to an off state.
Our future collaboration aims to provide structural insight into conserved co-transcriptional 3’ processing mechanisms that regulate transcriptional output and promote the switch to an epigenetically silenced state.