Genome-Wide Identification and Comparative Analysis of the TCP Transcription Factor Family in Three Glycyrrhiza Species Reveals GuTCP16 as a Positive Regulator of Salt Tolerance

The TCP transcription factor family is a plant-specific group of regulators with well-documented roles in mediating abiotic stress responses. Licorice (Glycyrrhiza) is a high-value medicinal crop of global economic significance, predominantly cultivated in arid and semi-arid environments where saline soils constrain seed germination, impair seedling development, and diminish both rhizome biomass and the accumulation of pharmacologically active metabolites. Despite the agronomic importance of this genus, a systematic genome-wide survey of the TCP family and its contribution to salt tolerance in Glycyrrhiza has not been reported. Here, we identified members of the TCP gene family at the whole-genome level in three representative species—G. uralensis, G. inflata, and G. glabra—and performed integrated bioinformatic characterization encompassing phylogenetic classification, chromosomal distribution, conserved motif architecture, physicochemical parameters, cis-regulatory element composition, and synteny analysis. Transcriptomic profiling revealed that Glycyrrhiza TCP genes display pronounced tissue-specific expression and undergo dynamic transcriptional reprogramming under saline conditions. Among the salt-responsive candidates, GuTCP16 emerged as a key regulator; it was confirmed to localize to the nucleus, and its heterologous expression in Arabidopsis enhanced plant performance under salt stress, demonstrating that GuTCP16 acts as a positive modulator of salt tolerance. Taken together, this work delineates the evolutionary features and functional diversification of the TCP family in Glycyrrhiza and identifies candidate genes to support molecular breeding efforts aimed at developing salt-resilient licorice cultivars.