Enhancement of the Expression of ZmBZR1 and ZmBES1 Regulatory Genes and Antioxidant Defense Genes Triggers Water Stress Mitigation in Maize (Zea mays L.) Plants Treated with 24-Epibrassinolide in Combination with Spermine

Abstract

Water shortages greatly threaten global food security and limit crop production. Hence, increasing crop water stress tolerance is a critical way to secure agricultural production. 24-Epibrassinolide (EBL) and spermine (Spm) are closely involved in plant growth and development, as well as stress tolerance. In this study, the potential role of 0.1 mg L−1 EBL and/or 25 mg L−1 Spm foliage applications in improving the tolerance ofmaize to water-deficit conditions (50% and 75% field capacity) was investigated. We found that EBL,either alone or in combination with Spm, plays a major role in maize drought tolerance through upregulating the expression of both regulatory genes (ZmBZR1 and ZmBES1) of the brassinosteroid signal transduction pathway and gene-encoding antioxidant defense enzymes ZmSOD, ZmCAT, ZmAPX, ZmMDHAR, ZmDHAR, and ZmGR. Moreover, exogenous treatments alleviated the inhibition of maize plant growth and productivity and mitigated drought-induced oxidative stress byimproving antioxidant enzyme (superoxide dismutase, catalase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase) activity, enhancing antioxidant molecule (ascorbate, glutathione) content, preventing reactive oxygen species accumulation, and maintaining cell membrane integrity. These findings reveal that the application of EBL, either individually or in combination with Spm, can be a goodstrategy for ameliorating water stress in sustainable agricultural systems.

Spermine-Salicylic Acid Interplay Restrains Salt Toxicity in Wheat (Triticum aestivum L.)

“…Regarding SPM application, it was reported that SPM can act as a signaling molecule, scavenge free radicals, and positively regulate the activity of antioxidant enzymes under saline environments [ 19 , 20 ]. Some researchers have proved exogenous SPM can increase the transcription level of antioxidant enzymes and then provoke antioxidant enzyme activity in plants under stressful conditions [ 18 , 39 ]. Overall, SA and SPM may have a role in improving wheat salt tolerance due to their ability to prevent ROS bursts.…”

Co-application of salicylic acid and spermine alleviates salt stress toxicity in wheat: growth, nutrient acquisition, osmolytes accumulation, and antioxidant response

“…This observation is corroborated by other studies, which state that SA is crucial in altering the performance of antioxidant enzymes, giving cells a better chance of surviving damage brought by salinity (Bukhat et al, 2020;Kaya et al, 2020;Xu et al 2020;Shamili et al 2021). Additionally, studies have proven that in response to environmental challenges, SPM promotes the efficiency of antioxidant enzymes (Igarashi and Kashiwagi 2019;Talaat et al 2022a).…”

“…Osmolyte production is essential for maintaining osmotic potential, metabolic activity, and water uptake under saline circumstances (Rady et al 2019;Talaat and Shawky 2022). Antioxidant enzymes also aid plants in preventing excessive ROS generation (Shamili et al 2021;Shopova et al 2021;Talaat et al 2022a). Moreover, ionic balance within the plant cell is essential for salt tolerance because excess salt ions in the cytoplasm disrupt ion homeostasis and impair plant development (Talaat 2019;Es-sbihi et al 2021).…”

“…Spermine (SPM) is a tetraamine that contributes to plant resistance to abiotic stress (Igarashi and Kashiwagi 2019;Talaat 2020). When applied exogenously, SPM can act as a potent plant defense activator (Todorova et al 2016;Seifi and Shelp 2019;Talaat et al 2022a). By scavenging ROS radicals, defending the structure and operation of the photosynthetic apparatus, maintaining cationic-anionic stability, lowering ethylene production, increasing protein content, modifying endogenous phytohormone levels, and inducing the accumulation of organic solutes, exogenously applied SPM lessens the detrimental impacts of salinity on plant development (Nahar et al 2016;Ahangera et al 2019;Islam et al 2020;Xu et al 2020;Geng et al 2021).…”

Plant Growth Stimulators Improve Two Wheat Cultivars Salt-Tolerance: Insights into Their Physiological and Nutritional Responses

“…Additionally, previous study provides evidence that the SPM application could maintain significantly higher root vitality, leaf relative water content, photosynthesis, water use efficiency, osmolytes accumulation, K + /Na + ratio, and antioxidant enzyme activity, as well as lower osmotic potential, Na + accumulation, and oxidative damage in salt-stressed creeping bentgrass plants [ 28 ]. Recently, it has been shown that exogenous SPM treatment alleviated the inhibition of maize plant growth and productivity under stressful conditions by improving the antioxidant enzyme activity, antioxidant molecules content, and cell membrane integrity [ 29 ]. Although several researchers have studied the effects of exogenous SPM on enhancing plant abiotic stress tolerance, not much is known about the mechanism of SPM associated with wheat salt tolerance.…”