Genome-wide characterization of the RCI2 gene family reveals conserved protein features and divergent responses to salt and osmotic stress in pea

Introduction Salinity and drought are major abiotic stresses limiting pea ( Pisum sativum L. ) growth and productivity. The RCI2 family has been implicated in plant responses to environmental stress, but its characteristics and potential roles in pea remain insufficiently understood. Methods Six PsRCI2 genes were identified and characterized using phylogenetic, gene structure, promoter, transcriptomic, quantitative real-time PCR (qRT-PCR), and subcellular localization analyses. Results PsRCI2-2 to PsRCI2-5 formed a gene cluster on chromosome 3, whereas no clear intragenomic collinear pairs were detected. Most PsRCI2 proteins showed conserved sequence and transmembrane features, whereas PsRCI2-6 exhibited distinct structural characteristics. Promoter analysis revealed diverse stress- and hormone-responsive cis-acting elements among family members. Transcriptome analysis revealed differential transcriptional responses to salt and PEG-induced osmotic stress. Notably, PsRCI2-2 , PsRCI2-3 , and PsRCI2-5 were induced by both treatments, and their expression patterns were validated by qRT-PCR. These three proteins also exhibited fluorescence patterns largely overlapping with the ER marker in Nicotiana benthamiana . Discussion The pea RCI2 family displays conserved structural features but divergent transcriptional responses. PsRCI2-2 , PsRCI2-3 , and PsRCI2-5 are promising candidates for further functional studies investigating pea responses to abiotic stress.