Comparative transcriptomic and correlation analyses revealed the vital role of PoCHX18 in the salt stress response of purslane (Portulaca oleracea)

Portulaca oleracea, a salt-tolerant plant endowed with both medicinal and nutritional properties, represents a high-value crop with significant potential for cultivation in saline-alkali agricultural systems. However, the salt tolerance regulatory mechanism of this organism remains incompletely characterized, with the functional roles of cation/H⁺ transporters being particularly poorly understood. In this study, transcriptomic sequencing was performed to identify differentially expressed genes in the roots and shoots of P. oleracea under salt stress conditions, with the aim of elucidating the molecular mechanisms underlying salt stress responses in P. oleracea and uncovering the functional roles of key regulatory genes. Through integrated gene co-expression analysis, the candidate gene PoCHX18, which exhibited a strong association with salt stress response, was identified from RNA-Seq data. PoCHX18 belonged to the cation/H⁺ antiporter family, while subcellular localization assays confirmed its membrane localization. The heterologous expression of PoCHX18 in Arabidopsis markedly enhanced seed germination rates and primary root elongation of seedlings under salt stress conditions, while protecting the reactive oxygen species (ROS) scavenging system and decreasing water loss rate. Further investigations revealed that PoCHX18 modulated Na⁺ and K⁺ ion homeostasis in both leaf and root tissues of transgenic lines, concomitantly with a significant upregulation of sodium transporter-associated genes, including AtHKT1, AtNHX2, AtSOS3, and particularly AtNRT1.1. Overall, this study elucidates the vital role and regulatory mechanism of PoCHX18 in the salt stress response of P. oleracea, thereby providing novel molecular insights into the adaptive evolutionary mechanisms of salt-tolerant plants, along with valuable genetic resources and theoretical frameworks for the genetic enhancement of salt-tolerant crops.