We conducted a study to examine the growth and physiological changes in 12 different ecotypes of Sesuvium portulacastrum collected from Hainan Island in China. These ecotypes were subjected to different concentrations (0, 200, 400, and 600 mmol/L) of sodium chloride (NaCl) salt stress for 14 days. We also analyzed the expression of metabolic genes related to stress response. Under low salt stress, indicators such as plant height in region K (0 mmol/L: 45% and highest at 200 mmol/L: 80%), internode length (0 mmol/L: 0.38, 200 mmol/L: 0.87, 400 mmol/L: 0.25, and 600 mmol/L: 1.35), as well as leaf area, relative water content, fresh weight, and dry weight exhibited an overall increasing trend with the increase in salt concentration. However, as the salt concentration increased, these indicators showed a decreasing trend. Proline and malondialdehyde contents increased with higher salt concentrations. When the NaCl concentration was 400 mmol/L, MDA content in the leaves was highest in the regions E (196.23%), F (94.28%), J (170.10%), and K (136.08%) as compared to the control group, respectively. Most materials demonstrated a significant decrease in chlorophyll a, chlorophyll b, and total chlorophyll content compared to the control group. Furthermore, the ratio of chlorophyll a to chlorophyll b (Rab) varied among different materials. Using principal component analysis, we identified three ecotypes (L from Xinglong Village, Danzhou City; B from Shuigoupo Village, Lingshui County; and J from Haidongfang Park, Dongfang City) that represented high, medium, and low salt tolerance levels, respectively, based on the above growth and physiological indexes. To further investigate the expression changes of related genes at the transcriptional level, we employed qRT-PCR. The results showed that the relative expression of SpP5CS1, SpLOX1, and SpLOX1 genes increased with higher salt concentrations, which corresponded to the accumulation of proline and malondialdehyde content, respectively. However, the relative expression of SpCHL1a and SpCHL1b did not exhibit a consistent pattern. This study contributes to our understanding of the salt tolerance mechanism in the true halophyte S. portulacastrum, providing a solid theoretical foundation for further research in this field.

Plants are frequently exposed to various abiotic stresses during their growth and development. S. portulacastrum possesses inherent tolerance to salinity and heavy metals, yet the underlying molecular mechanisms remain poorly understood. In this study, we performed a comprehensive analysis of S. portulacastrum by integrating full-length transcriptome sequencing and RNA sequencing (RNA-seq) under salt stress conditions. Transcriptome analysis identified 2839 and 1813 DEGs in leaves and 7328 and 754 DEGs in roots at 7 and 14 ds after NaCl treatment, respectively. Pathway enrichment analysis indicated that these DEGs were significantly enriched in pathways associated with Photosynthesis, plant hormone signal transduction, Linoleic acid metabolism, chlorophyll metabolism, and amino acid metabolism. Expression profiling showed that JAZ subfamily genes were significantly upregulated in both leaves and roots under salt and Cd stress. We cloned SpJAZ1, SpJAZ5, and SpJAZ7, and generated their overexpression lines in Arabidopsis. Physiological assays demonstrated that overexpression of SpJAZ1, SpJAZ5, and SpJAZ7 reduced hydrogen peroxide content by 29.07%, 20.62%, and 19.79%, respectively, and lowered the reduction in chlorophyll content (0.12, 0.15, and 0.17 μg/mL vs. 0.22 μg/mL). Meanwhile, proline content was increased in these lines (2.34, 2.08, and 2.05 μg/mL vs. 1.53 μg/mL), alongside enhancements in root length, lateral root number, and water content under salt stress. Importantly, these overexpression lines displayed a similar functional trend under Cd stress. Collectively, our results reveal potential crosstalk between the JA signaling pathway and stress mitigation pathways in S. portulacastrum in response to salt and Cd stresses.