Effects of salt stress on secretion of amino acids and their derivatives in root of Elytrigia elongata

doi:10.17521/cjpe.2025.0082

Abstract

Abstract:

Aims The objective of this study is to elucidate the response mechanism of amino acids and their derivatives secreted by the roots of salt-tolerant plants under salt stress.

Methods This study selected Elytrigia elongata as the research subject. Four levels of salt stress (CK, mild, moderate, and severe) were established by adding varying concentrations of NaCl. Non-targeted metabolomics analysis based on liquid chromatography-mass spectrometry (LC-MS) was employed to investigate the changing trends of root-secreted amino acids and derivatives in response to increasing salt stress intensity, as well as their relationships with root characteristics and the rhizosphere soil properties.

Important findings The results indicated that with escalating salt stress, the secretion of L-Arginine, L-Dopachrome, 2,3,4,5-Tetrahydropyridine-2,6-dicarboxylic acid, N-Acetyl aspartic acid, L-Phenylalanine, L-Methionine, trans-3-Hydroxy-L-proline, and N-Acetyl-L-phenylalanine significantly decreased. In contrast, betaine and N-Jasmonic acid isoleucine exhibited significant increases. However, no significant differences were observed in the abundance of betaine across mild, moderate, and severe stress conditions. There was only no significant difference in the abundance of N-jasmonic acid isoleucine between the mild stress group and the control group. Although the abundances of pipecolic acid and homomethionine exhibited a significant response to salt stress, they did not display a linear trend with increasing salt stress intensity. The secretion amounts of the other amino acids and derivatives showed no significant changes. These findings suggest that Elytrigia elongata adapts to salt-stressed environments by modulating the secretion of specific amino acids and derivatives. Soil salinity, electrical conductivity, volumetric water content, total root volume, and total root surface are key factors influencing the up-regulation of betaine and N-jasmonic acid isoleucine. Soil electrical conductivity serves as a key influencing factor for the secretion of eight down-regulated amino acids and their derivatives. Path analysis indicates that both the up-regulated and down-regulated groups of ten amino acids and their derivatives are regulated by soil electrical conductivity and pH. Collectively, these results provide a scientific foundation for understanding the physiological mechanisms underlying how plants adapt to salt stress.

Key words: Elytrigia elongata, salt stress, root exudates, amino acids, derivatives

HAO Huan-Huan, LI Dan, GUO Zi-Hua, ZHOU Ao, LI Yan-Jie, YANG Liang, ZHANG Ran, LU Ying-Shuai, ZHAO Xiang, CHEN Xiao-Peng. Effects of salt stress on secretion of amino acids and their derivatives in root of Elytrigia elongata[J]. Chin J Plant Ecol, 2026, 50(1): 202-212.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2025.0082

https://www.plant-ecology.com/EN/Y2026/V50/I1/202

Figures/Tables 6

Fig. 1 Effects of salt stress on the relative abundance of amino acids and their derivatives secreted by roots (mean ± SE). A, N-Jasmonic acid isoleucine. B, Betaine. C, L-Arginine. D, L-Dopachrome. E, 2,3,4,5-Tetrahydropyridine-2,6-dicarboxylic acid. F, N-Acetyl-L-aspartic acid. G, L-Phenylalanine. H, L-Methionine. I, Trans-3-Hydroxy-L-proline. J, N-Acetyl-L-phenylalanine. K, Biocytin. L, Citrulline. M, Pipecolic acid. N, Homomethionine. O, 4-Acetamidobutanoic acid. P, Saccharopine. CK, mild (Mi), moderate (Mo), severe (Se) stress NaCl concentrations were 0%, 0.2%, 0.4%, and 0.6%. Different lowercase letters indicate significant difference across different salt stress conditions (p < 0.05).

Fig. 2 Relative changes in the abundance of amino acids and their derivatives secreted by the roots of Elytrigia elongata (mean ± SE). Mild, moderate, severe stress NaCl concentrations were 0.2%, 0.4%, and 0.6%. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

Fig. 3 Principal Co-ordinates Analysis (PCoA) of the relative abundance of amino acids and their derivatives secreted by the roots of Elytrigia elongata. CK, mild, moderate, severe stress NaCl concentrations were 0%, 0.2%, 0.4%, and 0.6%.

Fig. 4 Pearson correlation analysis among environmental factors and Mantel test between environmental factors and the abundance of amino acids and their derivatives under salt stress. DOC, dissolved organic carbon content; DON, dissolved organic nitrogen content; EC, electrical conductivity; MBC, microbial biomass carbon content; MBN, microbial biomass nitrogen content; NH4+-N, ammonium nitrogen content; NO3--N, nitrate nitrogen content; Nort, number of root tips; Rmd, root average diameter; Tnor, total number of roots; Tpaor, total projected area of roots; Trl, total root length; Trsa, total root surface area; Trv, total root volume; VWC, volumetric water content. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

Fig. 5 Random forest model analysis of the contributions of the physical and chemical properties of rhizosphere soil and the traits of plant roots to the upregulated amino acids and their derivatives (A) and downregulated amino acids and their derivatives (B). IncMSE, increase in mean squared error. DOC, dissolved organic carbon content; DON, dissolved organic nitrogen content; EC, electrical conductivity; NH4+-N, ammonium nitrogen content; NO3--N, nitrate nitrogen content; Trl, total root length; Trsa, total root surface area; Trv, total root volume; VWC, volumetric water content. *, p < 0.05; **, p < 0.01; ns, p  0.05.

Fig. 6 Structural equation modeling of the abundances of amino acids and their derivatives secreted by roots that are upregulated (A) and downregulated (B) under salt stress. Red solid lines represent significant positive correlations, the gray solid lines indicate significant negative correlations, and the gray dashed lines denote non-significant effects. The numerical values next to the arrow denotes the normalized path coefficient, R2 denotes the interpretation degree of the model. GOF, goodness of fit. EC, electrical conductivity; Trl, total root length; Trv, total root volume. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

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