RCB initiates Arabidopsis thermomorphogenesis by stabilizing the thermoregulator PIF4 in the daytime

Nat Commun. 2021 Apr 6;12(1):2042. doi: 10.1038/s41467-021-22313-x.


Daytime warm temperature elicits thermomorphogenesis in Arabidopsis by stabilizing the central thermoregulator PHYTOCHROME INTERACTING transcription FACTOR 4 (PIF4), whose degradation is otherwise promoted by the photoreceptor and thermosensor phytochrome B. PIF4 stabilization in the light requires a transcriptional activator, HEMERA (HMR), and is abrogated when HMR's transactivation activity is impaired in hmr-22. Here, we report the identification of a hmr-22 suppressor mutant, rcb-101, which surprisingly carries an A275V mutation in REGULATOR OF CHLOROPLAST BIOGENESIS (RCB). rcb-101/hmr-22 restores thermoresponsive PIF4 accumulation and reverts the defects of hmr-22 in chloroplast biogenesis and photomorphogenesis. Strikingly, similar to hmr, the null rcb-10 mutant impedes PIF4 accumulation and thereby loses the warm-temperature response. rcb-101 rescues hmr-22 in an allele-specific manner. Consistently, RCB interacts directly with HMR. Together, these results unveil RCB as a novel temperature signaling component that functions collaboratively with HMR to initiate thermomorphogenesis by selectively stabilizing PIF4 in the daytime.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / genetics
  • Arabidopsis / physiology*
  • Arabidopsis / radiation effects
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Basic Helix-Loop-Helix Transcription Factors / metabolism*
  • Chlorophyll / metabolism
  • Chloroplasts / metabolism
  • Chloroplasts / radiation effects
  • Genes, Suppressor
  • Light
  • Models, Biological
  • Morphogenesis* / radiation effects
  • Photoperiod
  • Protein Stability / radiation effects
  • Seedlings / metabolism
  • Seedlings / radiation effects
  • Temperature*
  • Thioredoxins / chemistry
  • Thioredoxins / genetics
  • Thioredoxins / metabolism*
  • Transcription Factors / metabolism


  • Arabidopsis Proteins
  • At4g28590 protein, Arabidopsis
  • Basic Helix-Loop-Helix Transcription Factors
  • HMR protein, Arabidopsis
  • PIF4 protein, Arabidopsis
  • Transcription Factors
  • Chlorophyll
  • Thioredoxins