A transcription factor TaTCP20 regulates the expression of Ppd-D1b in common wheat

Photoperiod (Ppd) genes play an important role in the adaptation of wheat to the ecological environment. However, the transcriptional regulation mechanism of photoperiodic genes has remained elusive. This study isolated a full-length promoter of Ppd-D1b (2518 bp) from the common wheat genome. Several essential core cis-acting elements and numerous light-responsive cis-acting regulatory elements were identified in Ppd-D1b promoter by the in-silico analysis. Ten 5'-deleted length fragments of the Ppd-D1b promoter fused with GUS were constructed and named D0 ~ D9, then transferred them into Arabidopsis thaliana. GUS gene driven by full-length (D0) in transgenic Arabidopsis thaliana showed the same rhythm with Ppd-D1b in wheat under short-day conditions (SDs, 8-h light/16-h dark). The expression of GUS gene in D0 reached its peak at 3 h after dawn, then decreased to the lowest and remained stable. Analysis of the series of 5'-deleted fragments showed that at 3 h after dawn, GUS gene expression activity decreased significantly in D7a due to removal of CHEBS (CCA1 HIKING EXPEDITION binding site). Moreover, yeast one-hybrid (Y1H) and dual-luciferase (dual-LUC) assays revealed that TaTCP20 could bind to the Ppd-D1b promoter to increase its transcriptional activity. This study revealed a transcription factor, TaTCP20, which activated Ppd-D1b by binding to CHEBS, provided a foundation for the theoretical research on wheat's photoperiodic response mechanism.