Transcriptome and Metabolome Profiles Revealed Molecular Mechanisms Underlying Tolerance of Portulaca oleracea to Saline Stress

The purslane Portulaca oleraceae L. can tolerant high saline stress and has been developed as a seawater-irrigated vegetable. Currently, the underlying molecular mechanisms were still not well understood. In the present study, purslane seedlings were treated with 200 mM NaCl and then stems were subjected to transcriptome sequencing and metabolome analyses. Together with real-time quantitative PCR validation, the results showed that treatment with 200 mM NaCl depressed expression levels of genes for photosynthesis and aquaporins, suggesting that saline stress might inhibit photosynthesis and water uptake. However, expression levels of aminocyclopropane-1-carboxylic acid synthase, bifunctional L-3-cyanoalanine synthase/cysteine synthase and cyanoalanine synthase increased, suggesting elevation of ethylene production, which were further transduced by ethylene-responsive receptor and ethylene-insensitive 3 transcription factor. Metabolome analyses detected higher contents of pyrophosphate, D-galacturonic acid and elaidic acid in treatment with 200 mM NaCl than those in the control. These changes should positively regulate glycolysis, energy supply and integrity of cell membrane. Overall, changes of ethylene, pyrophosphate and elaidic acid might facilitate adaptation of purslane to saline stress.