PHYSIOLOGICAL AND MOLECULAR MECHANISMS UNDERLYING SALT STRESS TOLERANCE IN JOJOBA (SIMMONDSIA CHINENSIS)

The study aims to characterize the leaves of Jojoba (Simmondsia chinensis) under salt stress (50, 100, and 200 mM NaCl) at physiological and molecular levels. Physiological analysis included photosynthetic pigments of chlorophylls-a, and -b as well as carotenoids. H2O2 content as well as two antioxidant enzymes, namely catalase and ascothate peroxidase, were also analyzed. Overall results of physiological parameters indicated their differential response due to the stress. Molecular analysis, done via RNA-Seq and mapping highly expressed transcripts to KEGG pathways, resulted in a large number of regulated genes under salt stress, of which, 13 genes in six pathways were further studied referring to the studied physiological parameters. These genes included ALDO and TKT that promote both Calvin-Benson cycle and the production of eiythrose4-phosphate that acts upstream nine genes towards better growth under stress conditions. Other genes included HAO that mediates crosstalking of "carbon fixation in photosynthetic organisms" pathway and APX that participates in "Ascothate and aldarate metabolism" pathway. Overall, the six pathways were proven to crosstalk under salt stress in Jojoba to provide salt stress tolerance. This information can help using this plant as a source of biodiesel in salinized soil or areas of water scarce.