Seed Priming with Brassinosteroids Alleviates Chromium Stress in Rice Cultivars via Improving ROS Metabolism and Antioxidant Defense Response at Biochemical and Molecular Levels

Abstract

This research was performed to explore the vital role of seed priming with a 0.01 µM concentration of brassinosteroids (EBL) to alleviate the adverse effects of Cr (100 µM) in two different rice cultivars. Seed priming with EBL significantly enhanced the germination attributes (germination percentage, germination energy, germination index, and vigor index, etc.), photosynthetic rate as well as plant growth (shoot and root length including the fresh and dry weight) under Cr toxicity as compared to the plants primed with water. Cr toxicity induced antioxidant enzyme activities (SOD, POD, CAT, and APX) and ROS level (MDA and H2O2 contents) in both rice cultivars; however, a larger increment was observed in YLY-689 (tolerant) than CY-927 (sensitive) cultivar. EBL application stimulatingly increased antioxidant enzyme activities to scavenge ROS production under Cr stress. The gene expression of SOD and POD in EBL-primed rice plants followed a similar increasing trend as observed in the case of enzymatic activities of SOD and POD compared to water-primed rice plants. Simultaneously, Cr uptake was observed to be significantly higher in the water-primed control compared to plants primed with EBL. Moreover, Cr uptake was significant in YLY-689 compared to CY-927. In ultra-structure studies, it was observed that EBL priming relieved the rice plants from sub-cellular damage. Conclusively, our research indicated that seed priming with EBL could be adopted as a promising strategy to enhance rice growth by copping the venomous effect of Cr.

Screening of rice cultivars for Cr-stress response by using the parameters of seed germination, morpho-physiological and antioxidant analysis

“…Cr cause severe phytotoxic effects on plants growth, and biomass by decreasing the photosynthetic rate, disturbing mineral uptake balance, and increasing Cr uptake ( Singh et al, 2021 ). It is noticed that Cr stress cause reduction in seed germination rate, and disturb the antioxidative defense mechanism as well ( Basit et al, 2021a , Basit et al, 2021c , Basit et al, 2022 ). It is revealed that Cr uptake, and translocation minimize the germination, and growth ratio, negatively effects on chlorophyll pigments production, and PSII system, and increase electrolyte leakage by stimulating the ROS generation ( Wakeel et al, 2020 ), and ultimately crop yield is compromised.…”

“…In another study, it is noticed that nutrient, and Cr uptake competition cause Cr binding with carrier channels and plasma membrane, and weakened the H + ATPase activity ( Habiba et al, 2019 ). A current study represented that Cr-induced phytotoxicity reduce plants biomass, and photosynthetic ability by enhancing the stress markers such as malondialdehyde (MDA), and hydrogen peroxide (H 2 O 2 ), electrolyte leakage (EL), and Cr uptake inside Oryza sativa ( Basit et al, 2021a ), Sesbania sesban ( Din et al, 2020 ), Brassica napus ( Ulhassan et al, 2019b ), tomato ( Alamri et al, 2020 ), Spinacia oleracea ( Zaheer et al, 2020 ).…”

“…Although, Cr-toxicity also affects the antioxidant activities as well ( Ulhassan et al, 2019b , Wakeel et al, 2020 ). In general, Cr stress alter the biochemical, and physiological attributes of rice cultivars, and consequently lead to the growth inhibition, and crops yield loss ( Singh and Prasad, 2019 , Basit et al, 2021a , Sharma et al, 2022 ).…”

Approaches to Enhancing Antioxidant Defense in Plants

“…Phytohormone-based seed priming also proved to be effective against abiotic stress. Basit et al [21] concluded that seed priming with brassinosteroids (EBL) could be adopted as a promising strategy to enhance rice growth by copping the toxic effect of chromium (Cr). They [21] revealed that seed priming with a low dose (0.01 µM) of EBL could alleviate the adverse effects of Cr in two different rice cultivars.…”

“…Basit et al [21] concluded that seed priming with brassinosteroids (EBL) could be adopted as a promising strategy to enhance rice growth by copping the toxic effect of chromium (Cr). They [21] revealed that seed priming with a low dose (0.01 µM) of EBL could alleviate the adverse effects of Cr in two different rice cultivars. Seed priming with EBL stimulatingly increased antioxidant enzyme activities to scavenge ROS production under Cr stress.…”