Abstract
Peanut (Arachis hypogaea L.) is one of the five major oilseed crops cultivated worldwide. Salt stress is a common adverse condition for the growth of this crop in many countries and regions. In this study, physiological parameters and transcriptome profiles of peanut seedlings exposed to salt stress (250 mM NaCl for 4 days, S4) and recovery for 3 days (when transferred to standard conditions for 3 days, R3) were analyzed to detect genes associated with salt stress and recovery in peanut. We observed that the quantum yield of PSII electron transport (ΦPSII) and the maximal photochemical efficiency of PSII (Fv/Fm) decreased in S4 compared with the control, and increased in R3 compared with those in S4. Seedling fresh weight, dry weight and PSI oxidoreductive activity (ΔI/Io) were inhibited in S4 and did not recover in R3. Superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities decreased in S4 and increased in R3, whereas superoxide anion () and hydrogen peroxide (H2O2) contents increased in S4 and decreased in R3. Transcriptome analysis revealed 1,742 differentially expressed genes (DEGs) under salt stress and 390 DEGs under recovery. Among these DEGs, two DEGs encoding ω-3 fatty acid desaturase that synthesized linolenic acid (18:3) from linoleic acid (18:2) were down-regulated in S4 and up-regulated in R3. Furthermore, ω-3 fatty acid desaturase activity decreased under salt stress and increased under recovery. Consistent with this result, 18:3 content decreased under salt stress and increased under recovery compared with that under salt treatment. In conclusion, salt stress markedly changed the activity of ω-3 fatty acid desaturase and fatty acid composition. The findings provide novel insights for the improvement of salt tolerance in peanut.
Highlights
1,200 million ha of land are affected by salinity (Wicke et al, 2011)
250 mM NaCl caused a dramatic decrease in leaf length, leaf number, fresh weight (FW), dry weight (DW), and root length in peanut seedlings (Figures 1A,B)
These physiological indicators were not reversed by recovery treatment, which indicated that the growth of peanut seedlings was severely inhibited by salt stress and was not recovered when transferred to standard (ST) conditions
Summary
1,200 million ha of land are affected by salinity (Wicke et al, 2011). Salt stress is a common abiotic stress that adversely affects plant growth, development, and productivity worldwide (Kayani et al, 1990; Mahajan and Tuteja, 2005; Chen M. et al, 2010; Deng et al, 2015; Song and Wang, 2015). High salinity can affect many important biological processes in plants, Unsaturated Fatty Acid during Salt Stress including photosynthesis, protein synthesis, energy metabolism, and lipid metabolism (Carillo et al, 2011; Zhou et al, 2016). Fatty acid composition is essential as an energy reserve and for maintenance of membrane lipids (MataPérez et al, 2016). Cell membranes can sense the stress and initiate reactions to protect cells by adjusting the stress perception and rigidity of the cell structure. Function, and fluidity are largely affected by the lipid composition and unsaturated fatty acid content in plants (Mikami and Murata, 2003). Unsaturated fatty acids play a crucial role in protecting cell membranes and in maintaining the function of membrane proteins (Deuticke and Haest, 1987; Cooke and Burden, 1990)
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