Abstract:

TCP (TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR) proteins, a family of plant‐specific transcription factors, play important roles in many developmental processes. However, genetic and functional redundancy among class I TCP limits the analysis of their biological roles. Here, we identified a dominant‐negative mutant of Arabidopsis thaliana TCP7 named leaf curling‐upward (lcu), which exhibits smaller leaf cells and shorter hypocotyls than the wild type, due to defective endoreplication. A septuple loss‐of‐function mutant of TCP7, TCP8, TCP14, TCP15, TCP21, TCP22, and TCP23 displayed similar developmental defects to those of lcu. Genome‐wide RNA‐sequencing showed that lcu and the septuple mutant share many misexpressed genes. Intriguingly, TCP7 directly targets the CYCLIN D1;1 (CYCD1;1) locus and activates its transcription. We determined that the C‐terminus of TCP7 accounts for its transcriptional activation activity. Furthermore, the mutant protein LCU exhibited reduced transcriptional activation activity due to the introduction of an EAR‐like repressive domain at its C‐terminus. Together, these observations indicate that TCP7 plays important roles during leaf and hypocotyl development, redundantly, with at least six class I TCPs, and regulates the expression of CYCD1;1 to affect endoreplication in Arabidopsis.