A photoregulatory mechanism of the circadian clock in plants [RNA-seq]
Circadian clocks are the time-keeping cellular apparatuses that are photoentrained according to the day-night photocycles on Earth 1,2.  Cryptochromes (CRYs) are photoreceptors mediating photoentrainment of the circadian clock in plants and animals but how CRYs mediate light regulation of the molecular clock remains unclear 1,3.  Here we show that CRYs mediate photoresponses of the circadian clock by regulating the activity of N6-methyladenosine (m6A) RNA methyltransferase and photoresponses of the epitranscriptome.  In contrast to the presently known CRY complexome, the CRY2-methyltransferase complex exbibits multivalent interactions and photoresponsive condensation in response to blue light.  We show that photoexcited CRY2 undergoes phosphorylation-assisted demixing to form photobodies with the properties of condensed liquid phase, which facilitates assembly of the CRY2-methyltransferase complex in the condensed liquid phase of CRY2 in vivo.  The mta mutant impaired in m6A methyltransferase and the cry1cry2 mutant missing CRY photoreceptors share common defects of lengthened circadian period, reduced m6A RNA methylation, and accelerated degradation of mRNAs encoding core components of the molecular clock.  These results argue for a photoentrainment mechanism by which blue light elicits liquid-liquid phase separation of the CRY2-methyltransferase complex to regulate m6A mRNA methylation, consequently suppressing mRNA degradation and period lengthening of the circadian clock Overall design: RNA-seq of WT and cry1cry2 seedlings