Physiological, Biochemical, and Root Proteome Networks Revealed New Insights Into Salt Tolerance Mechanisms in Pongamia pinnata (L.) Pierre

Abstract

Cultivation of potential biofuel tree species such as Pongamia pinnata would rehabilitate saline marginal lands toward economic gains. We carried out a physiological, biochemical, and proteomic analysis to identify key regulatory responses which are associated with salt tolerance mechanisms at the shoot and root levels. Pongamia seedlings were grown at 300 and 500 mM NaCl (∼3% NaCl; sea saline equivalent) concentrations for 15 and 30 days, gas exchange measurements including leaf net photosynthetic rate (Asat), stomatal conductance (gs), and transpiration rate (E), and varying chlorophyll a fluorescence kinetics were recorded. The whole root proteome was quantified using the free-labeled nanoLC-MS/MS technique to investigate crucial proteins involved in signaling pathways associated with salt tolerance. Pongamia showed no visible salt-induced morphological symptoms. However, Pongamia showed about 50% decline in gas exchange parameters including Asat, E, and gs 15 and 30 days after salt treatment (DAS). The maximum potential quantum efficiency of photosystem (PS) II (Fv/Fm) was maintained at approximately 0.8 in salt-treated plants. The thermal component of PSII (DIo) was increased by 1.6-fold in the salt-treated plants. A total of 1,062 protein species were identified with 130 commonly abundant protein species. Our results also elucidate high abundance of protein species related to flavonoid biosynthesis, seed storage protein species, and carbohydrate metabolism under salt stress. Overall, these analyses suggest that Pongamia exhibited sustained leaf morphology by lowering net photosynthetic rates and emitting most of its light energy as heat. Our root proteomic results indicated that these protein species were most likely recruited from secondary and anaerobic metabolism, which could provide defense for roots against Na+ toxicity under salt stress conditions.

Transcriptome and Proteome Association Analysis to Screen Candidate Genes Related to Salt Tolerance in Reaumuria soongorica Leaves under Salt Stress

“…Since chalcone synthase is the first enzyme in the flavonoid biosynthetic pathway, its expression and regulation are important [57]. The significant enrichment of CHS protein in Pongamia roots under salt treatment contributes to the protection of Pongamia with high antioxidant activity from ROS damage and promotes root growth under high salt stress [58]. The results of this study showed that the abundance of CHS2 was significantly increased after the 500 mM NaCl treatment, indicating that R. soongorica could be used to increase secondary metabolites to mitigate salt damage by up-regulating the expression of CHS2.…”

Transcriptomic Profiling Reveals the Contribution of Nitric Oxide to Maintaining Photosynthesis and Antioxidant Ability in Hylotelephium erythrostictum Leaves under Salt Stress

“…Hence, leaves act as a bridge in the response to salt stress. Salt stress leads to a Na + and Climbalance, which damages photosystem II (PS II) in the chloroplast, resulting in an increased proportion of absorbed light energy being dissipated as heat and uorescence (Marriboina et al 2022). Na + slows the photosynthetic rate by disrupting proton dynamics, chloroplast function, and carbon xation enzyme activity (Van Zelm et al 2020).…”