The γ-Aminobutyric Acid (GABA) Alleviates Salt Stress Damage during Seeds Germination of White Clover Associated with Na⁺/K⁺ Transportation, Dehydrins Accumulation, and Stress-Related Genes Expression in White Clover.

Bizhen Cheng,Weihang Zeng,Yan Peng,Linlin Liang,Wei Liu,Linkai Huang,Xinquan Zhang,Zhou Li,Xiao Ma,Gang Nie,Yiqin Cao

doi:10.3390/ijms19092520

Bizhen Cheng, Weihang Zeng + Show 9 more

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https://doi.org/10.3390/ijms19092520

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Abstract

The objective of this study was to determine the effect of soaking with γ-aminobutyric acid (GABA) on white clover (Trifolium repens cv. Haifa) seed germination under salt stress induced by 100 mM NaCl. Seeds soaking with GABA (1 μM) significantly alleviated salt-induced decreases in endogenous GABA content, germination percentage, germination vigor, germination index, shoot and root length, fresh and dry weight, and root activity of seedling during seven days of germination. Exogenous application of GABA accelerated starch catabolism via the activation of amylase and also significantly reduced water-soluble carbohydrate, free amino acid, and free proline content in seedlings under salt stress. In addition, improved antioxidant enzyme activities (SOD, GPOX, CAT, APX, DHAR, GR and MDHR) and gene transcript levels (Cu/ZnSOD, FeSOD, MnSOD, CAT, GPOX, APX, MDHR, GPX and GST) was induced by seeds soaking with GABA, followed by decreases in O2∙−, H2O2, and MDA accumulation during germination under salt stress. Seeds soaking with GABA could also significantly improve Na+/K+ content and transcript levels of genes encoding Na+/K+ transportation (HKT1, HKT8, HAL2, H+-ATPase and SOS1) in seedlings of white clover. Moreover, exogenous GABA significantly induced the accumulation of dehydrins and expression of genes encoding dehydrins (SK2, Y2K, Y2SK, and dehydrin b) in seedlings under salt stress. These results indicate that GABA mitigates the salt damage during seeds germination through enhancing starch catabolism and the utilization of sugar and amino acids for the maintenance of growth, improving the antioxidant defense for the alleviation of oxidative damage, increasing Na+/K+ transportation for the osmotic adjustment, and promoting dehydrins accumulation for antioxidant and osmotic adjustment under salt stress.

Highlights

It has been reported that over 900 million hectares of land is negatively affected by salinity, accounting for 7% of the world’s total land [1]
Seeds soaking with the different concentration of GABA did not have significant effects on seedlings fresh weight (FW), dry weight (DW), root length (RL), shoot length (SL), and shoot-root ratio (Table 2)
Seeds priming with exogenous GABA (1 μM) had significantly higher seedlings DW, longer SL, and shoot-root ratio than seeds priming with water in response to salt stress (Table 2)

Summary

Introduction

It has been reported that over 900 million hectares of land is negatively affected by salinity, accounting for 7% of the world’s total land [1]. Salt stress seriously reduces the ability of plants taking up water resulting in physiological drought [3,4,5,6]. Those negative effects directly or indirectly lead to the overaccumulation of reactive oxygen species (ROS) which cause oxidative damage in plants under salt stress [7]. It is well-known that salt stress negatively affects all vegetative stages of plants, especially for seed germination [8]. Previous studies have indicated that salt stress significantly reduced germination percentage, germination vigor, shoot and root length of different plant species [9,10,11]

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