Ethylene Suppresses Abscisic Acid, Modulates Antioxidant System to Counteract Arsenic-Inhibited Photosynthetic Performance in the Presence of Selenium in Mustard

Abstract

Arsenic (As) stress provokes various toxic effects in plants that disturbs its photosynthetic potential and hampers growth. Ethylene and selenium (Se) have shown regulatory interaction in plants for metal tolerance; however, their synergism in As tolerance through modification of the antioxidant enzymes and hormone biosynthesis needs further elaboration. With this in view, we investigated the impact of ethylene and Se in the protection of photosynthetic performance against As stress in mustard (Brassica juncea L.). Supplementation with ethephon (2-chloroethylphosphonic acid; ethylene source) and/or Se allayed the negative impact of As-induced toxicity by limiting As content in leaves, enhancing the antioxidant defense system, and decreasing the accumulation of abscisic acid (ABA). Ethylene plus Se more prominently regulated stomatal behavior, improved photosynthetic capacity, and mitigated As-induced effects. Ethephon in the presence of Se decreased stress ethylene formation and ABA accumulation under As stress, resulting in improved photosynthesis and growth through enhanced reduced glutathione (GSH) synthesis, which in turn reduced the oxidative stress. In both As-stressed and non-stressed plants treated with ethylene action inhibitor, norbornadiene, resulted in increased ABA and oxidative stress with reduced photosynthetic activity by downregulating expression of ascorbate peroxidase and glutathione reductase, suggesting the involvement of ethylene in the reversal of As-induced toxicity. These findings suggest that ethephon and Se induce regulatory interaction between ethylene, ABA accumulation, and GSH metabolism through regulating the activity and expression of antioxidant enzymes. Thus, in an economically important crop (mustard), the severity of As stress could be reduced through the supplementation of both ethylene and Se that coordinate for maximum stress alleviation.

Involvement of ethylene in melatonin‐modified photosynthetic‐N use efficiency and antioxidant activity to improve photosynthesis of salt grown wheat

“…Ethylene has long been documented as a significant modulator of plant stress responses by acting as a signaling chemical, primarily inhibiting ROS generation and strengthening the antioxidant defense system (Gautam et al, 2022; Khan et al, 2016; Rather et al, 2022; Sehar et al, 2021; Sehar, Iqbal, et al, 2022). In the present study, salt stress treatment increased ethylene production to a higher level, regarded as stress ethylene, together with a maximum glucose level that adversely impacted the growth and development of the plants.…”

“…The regulation of enzymes of the ascorbate‐glutathione cycle by ethylene have been shown earlier in plants under different stress environments (Fatma et al, 2021; Gautam et al, 2022; Jiang et al, 2018; Masood et al, 2012; Qin et al, 2008; Rather et al, 2022; Sehar et al, 2021; Wang et al, 2020). This improvement in photosynthetic efficacy attributed to the optimization of stress ethylene resulted in reduced ROS generation via enhanced antioxidant enzyme activity (Khan et al, 2016; Masood et al, 2012; Sehar et al, 2021; Sehar, Iqbal, et al, 2022). Prior reports demonstrated that melatonin treatment increased ethylene production in grapevine by promoting ACC synthesis via MYB108A expression (Xu et al, 2019).…”

“…Further, a reduction in net photosynthesis and growth on AVG treatment compared with melatonin and salt-treated plants suggested an ethylenemediated effect of melatonin under salt stress. The involvement of ethylene in the reversal of abiotic stress has been shown (Gautam et al, 2022;Masood et al, 2012;Sehar, Gautam, et al, 2022;Sehar, Iqbal, et al, 2022). for growth that reduced its level and increased photosynthesis to compensate for the utilized glucose.…”

“…Exogenous application of melatonin has been found beneficial in reducing the salinitymediated decrease in growth characteristics in various crop plants, including Triticum aestivum, Oryza sativa, Avena sativa, Bermudagrass and tomato (Altaf et al, 2021;Gao et al, 2019;Hu et al, 2016;Iqbal et al, 2021;Yan et al, 2021). It has been previously shown that ethylene improves leaf area by greater differentiation of cells for higher photosynthesis and plant dry mass (Gautam et al, 2022;Sehar, Iqbal, et al, 2022). Aldesuquy et al (2014) has been shown due to Na + accumulation and changes in the fine structure of chloroplasts (Majid et al, 2021) or due to the increased chlorophyllase activity (Iqbal et al, 2021).…”

“…Ethylene, a key regulator in plant growth and development, plays many roles in plant abiotic stress acclimation, including salinity stress (Ahammed & Li, 2022; Fatma et al, 2022; Gautam et al, 2022; Sehar, Gautam, et al, 2022; Sehar, Iqbal, et al, 2022). Ethylene is also a positive mediator of adaptive responses under salt stress by upregulating antioxidant metabolism, synthesis of compatible osmolytes, and maintaining N‐use efficiency under N‐deficiency (Sehar et al, 2021).…”