Integrating Transcriptome and Physiological to Uncover the Mechanisms of Cell Enlargement in Promoting Organ Succulence in Suaeda Salsa

Abstract

Suaeda salsa, a typical euhalophyte, is a model halophyte for studying salt tolerance, with leaf succulence being a crucial factor in its response to salt stress. However, the molecular mechanisms underlying cell enlargement in organ succulence remain poorly understood. This study integrates transcriptome and physiological analyses to investigate the effects of sodium chloride (NaCl), calcium chloride (CaCl2), and their combined treatments on leaf succulence in S. salsa. The results show that NaCl, CaCl2, and their combined treatments significantly increased both leaf succulence and epidermal cell size. Moreover, these treatments led to an increase in the content of cellulose, hemicellulose, and pectin, along with the upregulation of cell wall remodeling genes (XTHs, EXPs, and LRXs) in the leaves of S. salsa, which together enhanced cell wall extensibility. Protein-protein interaction network analysis further revealed that SAUR19 in the auxin signaling pathway exhibited a significant relationship with EXPA10, a gene related to cell wall extensibility (Combined score = 0.638). The expression of SAUR genes was notably upregulated under NaCl, CaCl2, and their combined treatments. These results indicate that auxin may play a key role in the leaf succulence process. Additionally, the increased concentrations of Na+, Cl-, and Ca2+ resulted in higher water content in S. salsa leaves. This increase in water content drove cell expansion, promoting organ succulence. These findings suggest that ion homeostasis, auxin signaling, and cell wall remodeling mediate succulence in S. salsa under salt stress

Keywords: Succulence, Auxin, Cell wall, Suaeda salsa.