Salvianolic Acid Modulates Physiological Responses and Stress-Related Genes That Affect Osmotic Stress Tolerance in Glycine max and Zea mays

Abstract

Drought is a serious threat worldwide to soybean and maize production. This study was conducted to discern the impact of salvianolic acid treatment on osmotic-stressed soybean (Glycine max L.) and maize (Zea mays L.) seedlings from the perspective of physiochemical and molecular reactions. Examination of varied salvianolic acid concentrations (0, 0.1, 1, 5, 10, and 25 μM) on soybean and maize seedling growth confirmed that the 0.1 and 1 μM concentrations, respectively, showed an improvement in agronomic traits. Likewise, the investigation ascertained how salvianolic acid application could retrieve osmotic-stressed plants. Soybean and maize seedlings were irrigated with water or 25% PEG for 8 days. The results indicated that salvianolic acid application promoted the survival of the 39-day-old osmotic-stressed soybean and maize plants. The salvianolic acid-treated plants retained high photosynthetic pigments, protein, amino acid, fatty acid, sugar, and antioxidant contents, and demonstrated low hydrogen peroxide and lipid contents under osmotic stress conditions. Gene transcription pattern certified that salvianolic acid application led to an increased expression of GmGOGAT, GmUBC2, ZmpsbA, ZmNAGK, ZmVPP1, and ZmSCE1d genes, and a diminished expression of GmMIPS2, GmSOG1, GmACS, GmCKX, ZmPIS, and ZmNAC48 genes. Together, our results indicate the utility of salvianolic acid to enhance the osmotic endurance of soybean and maize plants.

Keywords: amino acid; antioxidant enzymes; fatty acid; hydrogen peroxide; lipid metabolism; protein; sugar.

Figure 1

Impact of salvianolic acid on soybean and maize plant growth and root under normal and stress conditions 8 days post-treatment (A–D). Treatments: Cont (control), SAL (0.1 μM salvianolic acid), SAL (1 μM salvianolic acid), PEG (25% polyethylene glycol), SAL (0.1 μM salvianolic acid) + PEG (25% polyethylene glycol), and SAL (1 μM salvianolic acid) + PEG (25% polyethylene glycol). Values show the means ± SE (n = 6) and significant differences at p < 0.05 (Tukey test).

Figure 2

Impact of salvianolic acid on soybean and maize plant growth parameters under normal and stress conditions 8 days post-treatment (A–T). Treatments: Cont (control), SAL (0.1 μM salvianolic acid), SAL (1 μM salvianolic acid), PEG (25% polyethylene glycol), SAL (0.1 μM salvianolic acid) + PEG (25% polyethylene glycol), and SAL (1 μM salvianolic acid) + PEG (25% polyethylene glycol). Values show the mean ± SE (n = 6) and significant differences at p < 0.05 (Tukey's test). Bars with different lowercase letters are significantly different from each other.

Figure 3

Effect of salvianolic acid application on soybean and maize plant photosynthetic parameters “chlorophyll a, Chla; chlorophyll b, Chlb; total chlorophyll, total Chl; and carotenoid contents” (A,B). Treatments: Cont (control), SAL (0.1 μM salvianolic acid), SAL (1 μM salvianolic acid), PEG (25% polyethylene glycol), SAL (0.1 μM salvianolic acid) + PEG (25% polyethylene glycol), and SAL (1 μM salvianolic acid) + PEG (25% polyethylene glycol). Values show the mean ± SE (n = 6) and significant differences at p < 0.05 (Tukey's test). Bars with different lowercase letters are significantly different from each other.

Figure 4

Effect of salvianolic acid application on amino acid content in leaves of soybean and maize grown under normal and stress conditions 8 days post-treatment (A,B). Treatments: Cont (control), SAL (0.1 μM salvianolic acid), SAL (1 μM salvianolic acid), PEG (25% polyethylene glycol), SAL (0.1 μM salvianolic acid) + PEG (25% polyethylene glycol), and SAL (1 μM salvianolic acid) + PEG (25% polyethylene glycol). Values show the mean ± SE (n = 6) and significant differences at p < 0.05 (Tukey's test). Bars with different lowercase letters are significantly different from each other.

Figure 5

(A) H₂O₂, (B) MDA, (C) total fatty acid, (D) protein, and (E) sugar content in leaves of soybean and maize grown under normal and stress conditions and treated with salvianolic acid for 8 days (8DAT). Treatments: Cont (control), SAL (0.1 μM salvianolic acid), SAL (1 μM salvianolic acid), PEG (25% polyethylene glycol), SAL (0.1 μM salvianolic acid) + PEG (25% polyethylene glycol), and SAL (1 μM salvianolic acid) + PEG (25% polyethylene glycol). Values show the mean ± SE (n = 6) and significant differences at p < 0.05 (Tukey's test). Bars with different lowercase letters are significantly different from each other.

Figure 6

Effect of salvianolic acid application on antioxidant content “SOD (A); CAT (B); DPPH (C); Flavonoids (D); Total polyphenol (E); POD (F); PPO (G)” of soybean and maize leaves grown under normal and stress conditions 8 days post-treatment. Treatments: Cont (control), SAL (0.1 μM salvianolic acid), SAL (1 μM salvianolic acid), PEG (25% polyethylene glycol), SAL (0.1 μM salvianolic acid) + PEG (25% polyethylene glycol), and SAL (1 μM salvianolic acid) + PEG (25% polyethylene glycol). Values show the mean ± SE (n = 6) and significant differences at p < 0.05 (Tukey's test). Bars with different lowercase letters are significantly different from each other.

Figure 7

Real-time expression analysis of GmMIPS2 (A), GmGOGAT (B), GmSOG1 (C), GmACS (D), GmUBC2 (E), GmCKX (F), ZmpsbA (G), ZmNAGK (H), ZmPIS (I), ZmVPP1 (J), ZmSCE1d (K), and ZmNAC48 (L) in leaves of soybean and maize plants grown under normal and stress conditions and treated with salvianolic acid for 8 days (8DAT). Treatments: Cont (control), SAL (0.1 μM salvianolic acid), SAL (1 μM salvianolic acid), PEG (25% polyethylene glycol), SAL (0.1 μM salvianolic acid) + PEG (25% polyethylene glycol), and SAL (1 μM salvianolic acid) + PEG (25% polyethylene glycol). Values show the mean ± SE (n = 6) and significant differences at p < 0.05 (Tukey's test). Bars with different lowercase letters are significantly different from each other.