Unveiling the protective role of anthocyanin in rice: insights into drought-induced oxidative stress and metabolic regulation

Abstract

This study investigates the impact of anthocyanin treatment on rice plants under drought stress, focusing on phenotypic, molecular, and biochemical responses. Anthocyanin were treated to one month old plants one week before the droughtexposure. Drought stress was imposed by using 10% polyethylene glycol (PEG 6000). Anthocyanin-treated plants exhibited significant enhancements in various traits, including growth parameters and reproductive characteristics, under normal conditions. When subjected to drought stress, these plants displayed resilience, maintaining or improving essential morphological and physiological features compared to non-treated counterparts. Notably, anthocyanin application mitigated drought-induced oxidative stress, as evidenced by reduced levels of reactive oxygen species (ROS) and lipid membrane peroxidation. The study also elucidates the regulatory role of anthocyanins in the expression of flavonoid biosynthetic genes, leading to increased levels of key secondary metabolites. Furthermore, anthocyanin treatment influenced the levels of stress-related signaling molecules, including melatonin, proline, abscisic acid (ABA), and salicylic acid (SA), contributing to enhanced stress tolerance. The enzymatic activity of antioxidants and the expression of drought-responsive genes were modulated by anthocyanins, emphasizing their role in antioxidant defense and stress response. Additionally, anthocyanin treatment positively influenced macronutrient concentrations, particularly calcium ion (Ca⁺), potassium ion (K⁺), and sodium ion (Na⁺), essential for cell wall and membrane stability. The findings collectively highlight the multifaceted protective effects of anthocyanins, positioning them as potential key players in conferring resilience to drought stress in rice plants. The study provides valuable insights into the molecular and physiological mechanisms underlying anthocyanin-mediated enhancement of drought stress tolerance, suggesting promising applications in agricultural practices for sustainable crop production.

Keywords: abscisic acid; anthocyanin; antioxidants; drought stress; melatonin.

Figure 1

Anthocyanin enhance rice phenotypic traits under drought stress. (A) is pictorial presentation of plant length and development, (B) is pictorial presentation of leaf width, (C-K) Shows shoot length, Root length, Leaf width, Chlorophyll contents, Relative water contents, Panicle number, Panicle length, Number of seeds, and Seed weight of 100 grain respectively. Data in (C-K) were from three independent biological replicates ± SD, and means were compared using Bonferroni Post-Hoc test.*P<0.05, **P<0.01, ***P<0.001.

Figure 2

Anthocyanin application reduces oxidative stress induced by drought stress in rice plant. (A) shows In situ detection of oxidative damage in rice leaves, facilitated by the generation of reactive oxygen species. (B) O₂ concentration, (C) H₂O₂ concentration and (D). MDA concentration. (E, F) shows CAT and POD activity respectively. Trypan and DAB staining were used for O₂ ^•− and H₂O₂ detection. Data were analyzed in three independent biological replicates ( ± standard deviation, SD), and the means were compared using Bonferroni Post-Hoc test. * indicates p< 0.05, ** indicates p< 0.01, and *** indicates p< 0.001.

Figure 3

Anthocyanin application induces flavonoid biosynthesis pathway under drought stress. (A-D) shows naringenin, cyaniding, delphinidin, and total flavonoids contents respectively, in rice plants. (E-I) shows expression level of PAL, CHS, CHI, F3H, and ANS respectively. Data were analyzed in three independent biological replicates ( ± standard deviation, SD), and the means were compared using Bonferroni Post-Hoc test. * indicates p< 0.05, ** indicates p< 0.01, and *** indicates p< 0.001.

Figure 4

Anthocyanin regulates phyto-hormones and proline content in rice plant during drought stress. (A) melatonin, (B) proline, (C) ABA, and (D) SA contents. Data were analyzed in three independent biological replicates ( ± standard deviation, SD), and the means were compared using Bonferroni Post-Hoc test. * indicates p< 0.05, ** indicates p< 0.01, and *** indicates p< 0.001.

Figure 5

Anthocyanin application significantly regulates antioxidant activity and drought related gene in rice plant. (A) ABTS antioxidant capacity, (B) DPPH free radical scavenging capacity, (C) DHN gene expression, and (D) DREB gene expression. Data were analyzed in three independent biological replicates ( ± standard deviation, SD), and the means were compared using Bonferroni Post-Hoc test. * indicates p< 0.05, ** indicates p< 0.01, and *** indicates p< 0.001.

Figure 6

Anthocyanin enhances the accumulation of macronutrients during drought stress in rice plant. (A-C) are Ca, K, and Na concentration respectively. Data were analyzed in three independent biological replicates ± SD, and means were compared using Bonferroni Post-Hoc test.*P<0.05,**P<0.001, ***P<0.001.