TLWD scaffold proteins sustain circadian function in Arabidopsis

Circadian rhythms control critical agricultural traits such as growth, biomass, flowering and response to environmental stress. In Arabidopsis, most circadian oscillator components are DNA-binding proteins that work at specific times of the day. In contrast, we have discovered a unique essential function of WD40-repeat scaffold proteins from the TRANSPARENT TESTA GLABRA-1 (TTG1) subfamily (TLWD) at the core of circadian oscillator which was masked by subfuntionalization between the TTG1 and the LIGHT REGULATED WD (LWD) subclades of the protein family. Both transcriptome analysis and circadian reporter experiments indicate a multifunctional activity of TLWD in controlling time of the day specific transcriptional activation and repression. Consistently, TLWD interact with an array of clock activators and repressors that act sequentially through the day. While TLWD proteins were known to participate in transcriptional activator complexes, our data indicate a novel role of TLWD in transcriptional repression.