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One of the most significant abiotic stresses causing permanent harm to plant development is increased temperature over the plants’ ideal need for growth. Climate change will have a profound impact on agriculture and food security. It’s calculated that a slow anticipated rise in global temperature will significantly impact plant production, especially in the coming 10 years. Over the next 20 years, the average global temperature may rise by 1.5 degrees Celsius or more. As per the Intergovernmental Panel on Climate Change, with 2 degrees Celsius of global warming, heat extremes would more frequently surpass crucial tolerance limits for agriculture and health.
Importance of Nitric Oxide and Abscisic Acid
Nitric oxide (NO) is gaining popularity in the plant science community due to its role in plant stress resistance; nevertheless, its impacts on heat stress tolerance are still debated. It is an oxygen radicals gaseous molecule linked to a variety of biological activities in plants.
Because it is a tiny diatomic molecule with a short half-life and no charge, nitric oxide is an excellent diffusible chemical messenger in plant signalling. Several studies have concentrated on explaining the crucial role of NO in influencing various plant hormone-mediated development and stress responses.
NO might be a secondary messenger for other protecting chemicals. Diao et al. discovered that spermidine generated NO in tomatoes during chilling stress, which was necessary for freezing tolerance because its suppression decreased tolerance. Because NO may be a common signalling component for various elicitors and phytohormones, including ABA, its crosstalk is critical. Aside from NO, abscisic acid (ABA) is necessary for the plant’s response to abiotic stressors such as heat, water deprivation, and salt. It affects stomatal closure and the synthesis of many acclimation proteins.
Similarities between Abscisic acid and Nitric Oxide
Guan and colleagues discovered that ABA has a function in controlling the expression of the Cat1 gene in late maize embryogenesis in maize under osmotic stress. Zhang et al. discovered ZFP36, a C2H2-type zinc finger protein, for ABA-induced antioxidant defense, resulting in rice tolerance to water and oxidative stress. In maize, drought and high temperatures were attributed to ABA-induced antioxidant defense via HSP70 [56]. ABA was necessary for Arabidopsis P5CS gene expression during salt stress. Proline, glycine betaine (GB), and calcium have been implicated in thermotolerance and its induction by ABA [47,58,59] and NO. Nitric oxide was discovered to boost ABA production in wheat seedlings subjected to salinity stress and function downstream of ABA.
2022 antioxidants in ABA-induced proline buildup Nitric oxide has also been shown to increase proline accumulation in response to salt and osmotic stress. According to reports, NO is essential for ABA-dependent proline synthesis during salt stress. H2S, according to Li et al., promotes trehalose accumulation during heat stress, which aids heat tolerance.
Abscisic Acid Concentration
WITH MINOR ADJUSTMENTS, the ABA content was calculated using Hung and Kao’s approach. Fatma et al. go into depth about the method. ABA was measured spectrophotometrically at 405 nm (model PGR-1; Sigma-Aldrich, St. Louis, MO, USA).
NO Generation Determination
The formation of nitric oxide was validated by calculating the nitrite concentration using the technique of Zhou et al., with minor changes. The approach is described in full by Gautam et al. The absorbance of the mixture was measured at 540 nm, and the NO concentration was determined using a calibration curve produced with sodium nitrite as the reference.
In conclusion
The nitrite-dependent nitrate reductase route and a mechanism reliant on the nitric oxide associated 1 (NOA1) protein, albeit NOA1 is a NO synthase, creates NO in plants. Many physiological processes in plants are regulated by NO, including responses to phytohormones including ABA, cytokinin, auxin, gibberellins, salicylic acid, immunity against pathogens, senescence, etc blooming. The nia1nia2noa1 triple mutant’s lack of NO production resulted in ABA-hypersensitive stomatal closure, indicating a detrimental function for endogenous NO in ABA signalling.
