Genome-Wide Identification of the TCP Gene Family in Astragalus mongholicus and Analysis of Its Response Patterns to Abiotic Stress

Astragalus mongholicus is one of the original plant species of the medicinal herb Astragali Radix as recorded in the Chinese Pharmacopoeia, possessing significant medicinal value and being widely utilized worldwide. TCP transcription factors constitute a plant-specific transcription factor superfamily that plays essential regulatory roles in vegetative growth, organ development, and abiotic stress responses. However, the TCP gene family in A. mongholicus has not yet been systematically investigated, and its functional characteristics remain largely unknown. In this study, based on genome-wide data, a total of 25 AmTCP genes containing complete TCP domains were identified in A. mongholicus, and their protein properties, sequence alignment, gene structures, and phylogenetic relationships were systematically characterized using comprehensive bioinformatics tools. Promoter cis-element analysis revealed that the AmTCP promoter regions are enriched in cis-elements associated with hormones, light, and abiotic stresses (drought and salinity), suggesting their potential involvement in multiple signaling cascades. Furthermore, transcriptomic profiling combined with qRT-PCR validation demonstrated that AmTCP genes exhibit tissue-specific expression patterns and differential responses to salt stress and polyethylene glycol (PEG)-simulated drought stress. Notably, AmTCP3, AmTCP8, AmTCP11, AmTCP17, and AmTCP19 displayed tissue- and time-dependent alterations in expression under stress conditions, with AmTCP17 and AmTCP19 showing the most pronounced responsiveness. Collectively, our findings systematically elucidate the fundamental molecular characteristics of TCP transcription factors in A. mongholicus, providing a valuable reference for future investigations into the biological functions of this gene family during growth, development, and abiotic stress responses in this medicinal plant.