Chromatin and Antisense Transcript Dynamics Underlying Quantitative Gene Regulation

The study of adaptation in plants has led us into the dissection of conserved mechanisms that link antisense transcripts with chromatin dynamics. These mechanisms emerged from genetic and molecular analysis of flowering pathways that quantitatively modulate expression of the flowering repressor FLC in response to different environmental and developmental cues.

The flowering pathways involve different aspects of chromatin regulation and a set of antisense transcripts produced at the FLC locus. These antisense transcripts, collectively called COOLAIR, are alternatively spliced and polyadenylated, initiate in an R-loop covering the 3’ end of FLC and encompass the whole FLC sense transcription unit. The differentially processed forms of COOLAIR are associated with different FLC chromatin states via changes in recruitment of chromatin modifying complexes. The chromatin modification, transcription and antisense transcript processing are co-transcriptionally coupled. This results in feedback loops that reinforce high or low expression states at FLC. We propose that regulation of COOLAIR processing leads to temporal switching between expression states, resulting in quantitative modulation of FLC expression. The talk will describe our current understanding of these mechanisms.

Co-transcriptional coupling mechanisms such as this may be of widespread importance in the quantitative regulation of gene expression in many organisms.