Differential expression of genes associated with ROS homeostasis and cell wall modifications in leaves and roots P. pinnata
We monitored the expression levels of several key salt-responsive genes including antioxidant enzymes (CAT4, FeSOD, MnSOD, Cu/ZnSOD1, and Cu/ZnSOD1-like) and cell wall thickening enzymes (POD, PAL1, PAL2, CAD2, and CAD6) (Supplementary Figures 9A, 10 and 11).
Among the antioxidant genes CAT4 expression remained unchanged in leaves throughout the salt stress treatment and showed down-regulation at 8 DAS in both 300 and 500 mM salt stress. In leaves, different isoforms of SODs showed gradual and significant up-regulation under 300 mM salt treatment from 1 to 8DAS. However, under 500 mM NaCl treatment, the SOD isoforms showed significant up-regulation only till 4DAS, but declined at prolonged stress treatment at 8DAS. Among the cell-wall strengthening genes, only POD showed a strong up-regulation in leaves of 300 and 500 mM NaCl treated plants at all-points, while the other genes (PAL1, PAL2, CAD1 and CAD2) did not show any significant induction. CAD 6 showed significant increase in 300 mM NaCl treatment at 8DAS, while these levels were significantly down-regulated in 300 mM NaCl 1 and 4DAS as well as in 500 mM NaCl treated plants at 1, 4, and 8DAS.
In roots, the expression levels CAT4 were substantially up-regulated in 300 and 500 mM NaCl treated plants at 1, 4 and 8DAS respectively (Supplementary Figures 9B, 10 and 11). Among the antioxidant genes, CAT4 was significantly up-regulated only at 1DAS of 500 mM salt treatment. FeSOD also increased at all-time points in 300 mM salt treated plants and in 500 mM NaCl treatment at 4 and 8DAS. However, the expression levels of all other genes including MnSOD, Cu/ZnSOD1, Cu/ZnSOD1-like SOD, PAL1, 2, and CAD1, 2 and 6 were slightly changed in roots of salt treated plants.