Effect of progressive drought stress on physio-biochemical responses and gene expression patterns in wheat

Abstract

The study aimed to decipher the impact of multiple drought stress on wheat. To that effect, Geumgangmil, PL 337 (1AL.1RS), PL 371 (1BL.1RS), and PL 257 (1DL.1RS) seedlings were subjected to four treatments: G1 (control), G2 (stressed thrice with rewatering), G3 (stressed twice with rewatering), and G4 (single stressful event). The findings provided a comprehensive framework of drought-hardening effect at physiological, biochemical, and gene expression levels of drought-stressed wheat genotypes. The treatments resulted in differentially higher levels of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), soluble sugar, and proline accumulation, and reduced relative water content (RWC) in wheat plants. Photosynthetic pigment (chlorophyll and carotenoid) levels, the membrane stability index (MSI), and shoot biomass decreased dramatically and differently across genotypes, particularly in G3 and G4 compared to G2. The activity of antioxidant enzymes [ascorbate peroxidase (APX), superoxide dismutase (SOD), and catalase (CAT)] increased with the duration and severity of drought treatment. Furthermore, the relative expression of DREB, LEA, HSP, P5CS, SOD1, CAT1, APX1, RBCL, and CCD1 genes was higher in G2 than in other treatments. Drought hardening increased drought tolerance and adaptability in plants under G2 by enhancing growth and activating defensive mechanisms at the physio-biochemical and molecular levels. The findings of the study indicated that early drought stress exposure-induced acclimation (hardening), which enhanced tolerance to subsequent drought stress in wheat seedlings. The findings of this study will be useful in initiating a breeding program to develop wheat cultivars with improved drought tolerance.

Supplementary information: The online version contains supplementary material available at 10.1007/s13205-021-02991-6.

Keywords: Antioxidant defense; Drought hardening; Membrane stability; Osmoregulation; Photosynthetic activity transcriptional regulation.

Fig. 1

Schematic experimental setup. Drought stress was applied to four wheat genotype seedlings, Geumgangmil, PL 337, PL 371, and PL 257. Group 1 stands for control plants, Group 2 for plants exposed to first stress for 5 days, second stress for 10 days, and third stress for 15 days, Group 3 for plants exposed to direct second stress for 10 days and third stress for 15 days, and Group 4 denotes plants exposed to direct stress for 15 days, during the 15 days drought period. Drought treatments were terminated by 3 days rewatering regimes. DW dry weight, RWC relative water content, EL electrolyte leakage, MSI membrane stability index, MDA malondialdehyde, SOD/SOD1 superoxide dismutase, CAT/CAT1 catalase, APX/APX1 ascorbate peroxidase, P5CS Δ-1-pyrroline-5-carboxylate synthetase, HSP heat shock protein, DREB dehydration-responsive element-binding, LEA late embryogenesis abundant, RBCL ribulose-bisphosphate carboxylase, CCD1 carotenoid cleavage dioxygenase

Fig. 2

Effect of drought stress on chlorophyll (A), carotenoid (B), and relative water content (C), leaf dry weight (D), root dry weight (E), and root to shoot ratio (F) of four wheat genotypes. Values are means ± standard error (SE) of three independent samples. Different letters on vertical bars indicate significant differences between means at P ≤ 0.05

Fig. 3

Effect of drought stress on membrane stability index (MSI) (A), electrolyte leakage (EL) (B), and malondialdehyde (MDA) content (C), hydrogen peroxide (H₂O₂) accumulation (D) proline level (E), soluble sugar level (F), superoxide dismutase (SOD) activity (G), catalase (CAT) activity (H), and ascorbate peroxidase (APX) (I) activity of four wheat genotypes. Values are means ± standard error (SE) of three independent samples. Different letters on vertical bars indicate significant differences between means at P ≤ 0.05

Fig. 4

Relative expression levels of antioxidant-related genes in wheat seedlings of four genotypes (Geumgangmil, PL 337, PL 371, and PL 257) under drought stress. Expression patterns relative to that of Actin are shown for superoxide dismutase (SOD1) (A), catalase (CAT1) (B), and peroxidase (APX1) (C), Δ-1-pyrroline-5-carboxylate synthetase (P5CS) (D), heat shock proteins (HSP) (E), and dehydration-responsive element-binding (DREB) (F), late embryogenesis abundant (LEA) (G), ribulose-bisphosphate carboxylase (RBCL) (H), and carotenoid cleavage dioxygenase (CCD1) (I). Values are means ± standard error (SE) of three independent samples. Different letters on vertical bars indicate significant differences between means at P ≤ 0.05

Fig. 5

Principal component analysis (PCA) for physiological and molecular responses in four wheat genotypes under different drought treatments. Scree plot and biplot of variance explained by each factor of the principal component in Group 2 plants (A/D), Group 3 plants (B/E), and Group 4 plants (C/F). F1–F3 the first to third principal component

Fig. 6

Heat map of wheat genotypes (A), physiological (B), and molecular (C) indicators under different drought treatment conditions