Cobalt and Titanium Alleviate the Methylglyoxal-Induced Oxidative Stress in Pennisetum divisum Seedlings under Saline Conditions

Abstract

Salinity is considered to be a global problem and a severe danger to modern agriculture since it negatively impacts plants' growth and development at both cellular- and whole-plant level. However, cobalt (Co) and titanium (Ti), multifunctional non-essential micro-elements, play a crucial role in improving plant growth and development under salinity stress. In the current study, Co and Ti impact on the morphological, biochemical, nutritional, and metabolic profile of Pennisetum divisum plants under three salinity levels which were assessed. Two concentrations of Co (Co-1; 15.0 mg/L and Co-2; 25.0 mg/L), and two concentrations of Ti (Ti-1; 50.0 mg/L and Ti-2; 100.0 mg/L) were applied as foliar application to the P. divisum plants under salinity (S1; 200 mM, S2; 500 mM, and S3; 1000 mM) stress. The results revealed that various morphological, biochemical, and metabolic processes were drastically impacted by the salinity-induced methylglyoxal (MG) stress. The excessive accumulation of salt ions, including Na⁺ (1.24- and 1.21-fold), and Cl^- (1.53- and 1.15-fold) in leaves and roots of P. divisum, resulted in the higher production of MG (2.77- and 2.95-fold) in leaves and roots under severe (1000 mM) salinity stress, respectively. However, Ti-treated leaves showed a significant reduction in ionic imbalance and MG concentrations, whereas considerable improvement was shown in K⁺ and Ca²⁺ under salinity stress, and Co treatment showed downregulation of MG content (26, 16, and 14%) and improved the antioxidant activity, such as a reduction in glutathione (GSH), oxidized glutathione (GSSG), Glutathione reductase (GR), Glyoxalase I (Gly I), and Glyoxalase II (Gly II) by up to 1.13-, 1.35-, 3.75-, 2.08-, and 1.68-fold under severe salinity stress in P. divisum roots. Furthermore, MG-induced stress negatively impacted the metabolic profile and antioxidants activity of P. divisum's root and leaves; however, Co and Ti treatment considerably improved the biochemical processes and metabolic profile in both underground and aerial parts of the studied plants. Collectively, the results depicted that Co treatment showed significant results in roots and Ti treatment presented considerable changes in leaves of P. divism under salinity stress.

Keywords: glyoxalase pathway; methylglyoxal; microelements; plant diabetes; salinity stress; stress protectant.

Figure 1

Exogenous application of cobalt and titanium’s effect on ionic toxicity and nutrient uptake of Pennisetum divisum under salinity stress. (a) Na⁺ (sodium), (b) Cl⁻ (chloride), (c) K⁺ (potassium), (d) Ca²⁺ (calcium ion), CK (control treatment), Co-0 (0 mg/L), Co-1 (15 mg/L), Co-2 (25 mg/L), Ti-0 (0 mg/L), Ti-1 (50 mg/L), and Ti-2 (100 mg/L). The different letters above columns are significantly different from each other at p ≤ 0.05 levels in each parameter (ANOVA) followed by the least significant difference test.

Figure 2

Exogenous application of cobalt and titanium’s effect on MG-induced oxidative stress, and its scavenging enzymes of Pennisetum divisum under salinity stress. (a) Reduced glutathione (GSH), (b) oxidized glutathione (GSSG), (c) glutathione reducase (GR), (d) glyoxalase I (Gly I), (e) glyoxalase II (Gly II), (f) methylglyoxal (MG), CK (control treatment), Co-0 (0 mg/L), Co-1 (15 mg/L), Co-2 (25 mg/L), Ti-0 (0 mg/L), Ti-1 (50 mg/L), and Ti-2 (100 mg/L). The different letters above columns are significantly different from each other at p ≤ 0.05 levels in each parameter (ANOVA) followed by the least significant difference test.

Figure 3

Exogenous application of cobalt and titanium effect on the metabolic profile of Pennisetum divisum’s (a) leaves, and (b) roots under salinity stress. CK (control treatment), S1 (salinity 200 mM), S2 (Salinity 500 mM), S3 (Salinity 1000 mM), Co-1 (15 mg/L), Co-2 (25 mg/L), Ti-0 (0 mg/L), Ti-1 (50 mg/L), and Ti-2 (100 mg/L). The heatmap was developed using TBtools software using log-2 values. Each colored cell on the map corresponds to a normalized log-response value of the studied metabolic activity, with samples in columns and metabolites in rows. Red color represents the highest metabolic level, whereas blue color indicates the lowest metabolic levels.

Figure 4

Schematic diagram of metabolites involved in P. divisum’s tissues under salinity stress.