Genome-Wide Characterization of TCP Transcription Factors in Common Glasswort (Salicornia europaea) and Their Expression Analysis Under Salt Stress

TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) are plant-specific regulators involved in growth, development, and responses to abiotic stresses, yet their roles in halophytes remain largely unexplored. In this study, we performed a genome-wide identification of TCP family members in the extreme halophyte Salicornia europaea, uncovering 15 non-redundant genes (SeurTCPs) classified into PCF, CIN, and CYC/TB1 subfamilies. Gene structure and conserved motif analyses revealed that SeurTCPs are largely intronless and maintain the canonical TCP domain, while showing subfamily-specific variations in motif composition and secondary/tertiary structures. Promoter analysis identified abundant stress and hormone-responsive cis-elements, particularly ABRE and STRE, suggesting potential involvement in salt stress signaling. Protein–protein interaction network prediction highlighted CIN and PCF members as hub nodes, indicating central roles in growth and stress response regulation. Quantitative Real-Time Reverse Transcription Polymerase Chain Reaction (qRT-PCR) analysis showed that most SeurTCP genes were responsive to salinity treatment, although the extent of transcriptional variation differed among subfamilies. Collectively, our results indicate that SeurTCPs balance conserved structural functions with subfamily-specific regulatory roles, contributing to S. europaea adaptation to extreme saline environments. This study provides valuable candidate genes for elucidating plant salt tolerance mechanisms and for potential crop improvement.