Transcriptional Profiling Reveals a Time-of-day Specific Role of REVEILLE 4/8 in Regulating the First Wave of Heat Shock-induced Gene Expression in Arabidopsis
- THE PLANT CELL
- Although much is known about plant responses to heat shock (HS), how plants sense high temperature and the primary HS signal transduction pathway leading to HS-regulated gene expression are still poorly understood. To identify primary transcription factors that mediate HS-regulated gene expression and their target genes, RNA-seq was performed to detect genes whose expression is rapidly altered by HS in Arabidopsis thaliana. The results showed several genes were induced after only 5 min of HS treatment, suggesting that HS signaling occurs very rapidly. Analysis of the cis-elements in the promoters of genes upregulated by 10 min of HS treatment identified HEAT SHOCK FACTOR A1s (HSFA1s) and circadian clock proteins REVEILLE4/8 (RVE4/8) as essential transcription factors that independently mediate early HS-induced gene expression. Using hsfa1a/b/d/e and rve4/8 mutants, we identified subsets of HSFA1s- or RVE4/8-dependent early HS-induced genes, and showed RVE4/8 regulate plant thermotolerance partially by regulating the expression of downstream transcription factors ETHYLENE RESPONSIVE FACTOR53 (ERF53) and ERF54, specifically around noon. These findings reveal a potential transcriptional regulatory hierarchy governing the first wave of HS-induced gene expression. They also provided important insight into the mechanism by which the circadian clock gates thermotolerance and prepares plants for exposure to high temperatures during the day.