Integrating transcriptomic and physiological analyses to uncover the mechanisms of cell enlargement in promoting organ succulence in Suaeda salsa

Suaeda salsa ( S. salsa ), a typical euhalophyte, serves as a model halophyte for studying salt tolerance, with leaf succulence playing a key role in its response to salt stress. However, the molecular mechanisms underlying cell enlargement contributing to organ succulence remain poorly understood. This study integrates transcriptome and physiological analyses to investigate the effects of sodium chloride (NaCl), calcium chloride (CaCl 2 ), and their interaction treatment on leaf succulence in S. salsa . Results indicate that NaCl, CaCl 2 , and their combination significantly increase leaf succulence and epidermal cell size. These treatments also enhance the content of cellulose, hemicellulose, and pectin, along with the upregulation of cell wall remodeling genes ( XTHs , EXPs , and LRXs ), thereby improving cell wall extensibility. Protein–protein interaction network analysis further identified a strong association between SAUR19 (in the auxin signaling pathway) and EXPA10 , a gene related to cell wall loosening (Combined score = 0.638). SAUR gene expression was markedly upregulated under all treatments, suggesting a critical role for auxin in promoting succulence. Additionally, increased sodium, chloride, and calcium concentrations enhanced leaf water content, driving cell expansion and contributing to the succulence of organs. These findings demonstrate that ion homeostasis, auxin signaling, and cell wall remodeling collectively mediate succulence in S. salsa under salt stress. This study offers new insights into the molecular basis of organ succulence in halophytes. It offers theoretical insights for improving salt tolerance in crops, with potential applications in sustainable agriculture for regions with saline soils. • Na + and Ca 2+ increased gene expression of XTHs, EXPs, and LRXs to enhance leaf succulence. • Genes related to auxin signaling (SAURs) significantly correlated with EXPs and LRXs. • Auxin involved in the leaf succulence in S. salsa via cell wall remodeling.