Melatonin Enhances Drought Tolerance by Regulating Leaf Stomatal Behavior, Carbon and Nitrogen Metabolism, and Related Gene Expression in Maize Plants

Abstract

It is commonly known that exogenously applied melatonin can alleviate the impact of drought stress, but the mechanism used by melatonin to regulate stomatal behavior and carbon (C) and nitrogen (N) metabolism to increase drought resistance remains elusive. Herein, our aim was to investigate the influence of exogenous melatonin on the regulation of C and N metabolism in maize plants under water deficit. In this study, we analyzed stomatal behavior, the key components of C and N metabolism, and the gene expression and activity of enzymes involved in the C and N metabolism in maize plants. The results showed that the application of melatonin (100 μM) significantly increased maize growth and sustained the opening of stomata, and secondarily increased the photosynthetic capacity in maize. Under drought stress, foliar application of melatonin induced the gene transcription and activities of sucrose phosphate synthetase, ADP-glucose pyrophosphorylase, phosphoenolpyruvate carboxylase, and citrate synthase, resulting in the enhancement of sucrose and starch synthesis and the tricarboxylic acid (TCA) cycle. This enhancement in sugar biosynthesis and the TCA cycle might lead to stronger N assimilation. As anticipated, NO3– reduction and NH4+ assimilation were also strengthened after melatonin treatment under drought stress. An increase was observed in some key enzymatic activities and transcription involved in nitrogen metabolism, such as that of nitrate reductase, nitrite reductase, glutamate synthase, and glutamine synthetase, in melatonin-treated, drought-stressed maize. Moreover, melatonin attenuated the drought-induced damage by reducing protein degradation and increasing the level of proline. Conclusively, our results indicate that exogenous melatonin enhances drought tolerance in maize via promoting stomatal opening and regulating C and N metabolism and related gene expression.

Carex rigescens caffeic acid O-methyltransferase gene CrCOMT confer melatonin-mediated drought tolerance in transgenic tobacco

“…Melatonin is a multifunctional regulator in plant response to drought stress. (1) The accumulation of osmolytes, such as free proline, were enhanced in melatonin-treated plants, significantly alleviating adverse effects by facilitating the maintenance of optimum turgor pressure ( Zhao et al, 2021 ). (2) Melatonin induces the expression of transcription factors and modulates the expression of downstream stress-responsive genes, thereby increasing plant drought tolerance ( Sharma and Zheng, 2019 ).…”

“…Melatonin is a multifunctional regulator in plant response to drought stress. (1) The accumulation of osmolytes, such as free proline, were enhanced in melatonin-treated plants, significantly alleviating adverse effects by facilitating the maintenance of optimum turgor pressure (Zhao et al, 2021).…”

Effects of drought stress on flowering soybean physiology under different soil conditions

“…Under drought stress, the GS activity in silty loam was significantly higher than in sandy clay, and the GS activity in sandy clay was significantly higher than in clay loam. Studies have shown that under short-term or mild water stress, GS and GOGAT activities increase in the short term to remove previously metabolically accumulated NH 4 + ) in order to weaken or eliminate the toxic effects of NH 4 + accumulation on plant cells (Zhao et al 2021). However, when the stress time was too long, or the stress degree was too heavy, the activities of GS and GOGAT decreased significantly due to the limitation of NR activity (Zhao et al 2021).…”

“…Studies have shown that under short-term or mild water stress, GS and GOGAT activities increase in the short term to remove previously metabolically accumulated NH 4 + ) in order to weaken or eliminate the toxic effects of NH 4 + accumulation on plant cells (Zhao et al 2021). However, when the stress time was too long, or the stress degree was too heavy, the activities of GS and GOGAT decreased significantly due to the limitation of NR activity (Zhao et al 2021). It has also been suggested that the decrease in GS and GOGAT activity under severe drought or prolonged drought conditions is due to increased hydrolase activity (Cao et al 2022)…”

“…Plant, Soil and Environment, 68, 2022 (10): 487-498 Original Paper https://doi.org/10.17221/237/2022-PSE This may be a unique stress mode of soybean under drought stress, and finally, the activity of GS and GOGAT decreased due to the limitation of NR activity and drought stress (Du et al 2020, Zhao et al 2021.…”