TCPs

TCPs, or TCP transcription factors, are a family of plant-specific transcription factors characterized by a conserved noncanonical basic helix-loop- helix (bHLH) domain known as the TCP domain. The name derives from three early characterized members: TB1 (teosinte branched1), CYC (CYCLOIDEA), and PCF (proliferation factor).

Most TCPs function as DNA-binding proteins that bind promoters and regulate gene expression, often acting as homodimers or heterodimers. They are divided into two classes: class I (PCF-like) and class II (CYC/TB1-like). Class II members frequently contain an R domain and are commonly regulated by microRNA miR319, which post-transcriptionally silences several class II TCPs to control growth and development.

TCPs regulate diverse developmental processes, including leaf shape and size, leaf serration, branching architecture, flower and fruit development, and responses to hormones such as auxin, gibberellin, and jasmonic acid. They integrate environmental cues and developmental signals and can act as transcriptional activators or repressors depending on context and interacting partners.

Evolution and significance: TCPs are plant-specific and have diversified across land plants, with number and composition varying among species, often expanded by gene and genome duplications. In model species such as Arabidopsis thaliana and in crop plants, TCP genes are studied for their roles in plant architecture and organ development.