Genome-wide identification and characterization of Tetraspanin (TET) genes reveals their potential involvement in stress responses in Piper nigrum

Tetraspanins are a group of integral membrane proteins that are known to participate in cellular signaling, membrane organization, and plant stress responses. In this study, a genome-wide analysis was carried out to characterize tetraspanin gene family in black pepper ( Piper nigrum L.). A total of twelve P. nigrum tetraspanin ( PnTETs ) gene candidates were identified and classified into six groups, namely TET1, TET2, TET3, TET6, TET8, and TET10. The gene lengths ranged from 917 to 5154 bp, with coding sequences of 798–1491 bp encoding proteins of 265–496 amino acids. The predicted PnTET proteins were predominantly basic, with molecular weights between 29.3 and 53.5 kDa, and exhibited conserved structural features, including four transmembrane domains, cysteine-rich extracellular loops, and characteristic motifs. Promoter analysis of PnTET genes revealed a diverse array of hormone, stress, and light-responsive cis-elements that participate in environmental signals and developmental processes. Expression profiling of selected genes PnTET3.1, PnTET8.1, and PnTET10 in the cultivar Panniyur-1 showed distinct gene-specific responses under Phytophthora capsici infection and drought. PnTET3.1 showed strong and sustained induction under both stress conditions, indicating its potential role in stress signaling, whereas PnTET8.1 exhibited moderate upregulation, particularly under pathogen infection, indicating its possible association with defense responses. PnTET10 displayed early induction, indicating a role in initial stress perception. Furthermore, PnTET8 , PnTET3 , and PnTET10 were all upregulated under drought stress. Sequence characterization and phylogenetic analysis demonstrated that PnTET genes retain conserved structural features and evolutionary relationship with tetraspanins from other magnoliid species, supporting evolutionary conservation of this gene family. Overall, this study provides insights into the structure, evolution, and stress-responsive functions of tetraspanin genes in P. nigrum , offering a foundation for future functional studies aimed at stress-resilient cultivars.