TCP Transcription Factors: Evolution, Structure, and Biochemical Function

The Teosinte branched1/Cincinnata/proliferating cell factor (TCP) family is a group of genes encoding plant-specific transcription factors that share the so-called TCP domain, a 59-amino-acid stretch predicted to form a noncanonical basic helix–loop–helix (bHLH) structure. The TCP domain allows DNA binding and facilitates protein–protein interactions. TCP genes have been found across the plant kingdom, from green algae to eudicots. Gene duplication and diversification of the family members led to an increase in family size, so that more than 20 TCP genes are found in eudicots species. Two major clades (class I and II) of TCP proteins can be distinguished with slightly different TCP domains. In this chapter, we summarize recent work analyzing the evolution of the TCP family in angiosperms, as well as the biochemical role of TCP proteins as transcriptional regulators. We highlight the role of particular residues of the TCP domain in protein–DNA and protein–protein interactions, and discuss the involvement of other protein regions in their posttranslational regulation and function.