Two bHLH Transcription Factors, bHLH48 and bHLH60, Associate with PHYTOCHROME INTERACTING FACTOR 7 to Regulate Hypocotyl Elongation in Arabidopsis thaliana

A ChIP-Seq was performed using 35S::PIF7-Flash and 35S::bHLH60-Flag transgenic plants after 1 hr shade treatment. Approximately 6374 peaks (5262 genes) were considered as high-confidence of PIF7 binding peaks (Fold change > 2, q-value < 0.05). And 2278 peaks (2143 genes) were considered as high-confidence of bHLH60 binding peaks. The bound genes of PIF7 significantly overlapped with bHLH60-bound genes. And, the transcriptional levels of PIF7 and bHLH60 co-bound genes were also regulated by PIF7 and bHLH48/60. Our results indicated PIF7 and bHLH60 form a heterodimer to bind to promoters of the common target genes and regulate their expressions. 8-day-old white-light-grown seedlings were treated 1 hr shade before harvesting for DNA extraction.