Melatonin Promotes Seed Germination Under Salt Stress by Regulating ABA and GA3 in Cotton (Gossypium Hirsutum L.)

Abstract

Background: Although previous studies have found that melatonin can promote seed germination, the phytohormone regulation mechanism by which exogenous melatonin mediates salt tolerance during cotton seed germination is still largely unknown. We investigated the effect of melatonin on the germination traits and physiological parameters of GXM9 cotton seeds (Gossypium hirsutum L.) under three salt stress treatments (CK, germination of seeds pretreated with water alone; S, germination of seeds pretreated in 150 mM NaCl under salt stress; SM, germination of seeds pretreated in 20 µM melatonin under 150 mM NaCl solution) in the laboratory.Results: We found that salt stress (150 mM) inhibited cotton seed germination and endogenous melatonin accumulation, and pretreatment with 20 µM exogenous melatonin enhanced the cotton germination rate and hypocotyl length as well as the content of endogenous melatonin during seed germination. This suggests that exogenous melatonin promotes seed germination from a morphological perspective. The contents of starch, α-amylase (EC3.3.1.1), β-galactosidase (EC3.2.1.23), abscisic acid (ABA), and gibberellin (GA) were determined simultaneously. The results showed that the α-amylase and β-galactosidase contents in the cotton seeds decreased by 56.97% and 20.18%, respectively, under salt stress compared with the control, while the starch content increased by 11.53% compared with the control at day 7. The ABA content increased by 25.18% and GA content decreased by 27.99% under salt stress compared with the control at 24 h. When exogenous melatonin was applied to the cotton seeds, the content of α-amylase and β-galactosidase increased by 121.77% and 32.76%, respectively, whereas the starch contents decreased by 13.55% compared with the S treatment at day 7. Similarly, the ABA content increased by 12.20% and the GA content increased by 4.77% at 24 h. To elucidate the molecular mechanism by which melatonin promotes seed germination under salt stress, the effects of ABA- and GA-related genes on plant hormone signal transduction were analyzed by quantitative real-time PCR and RNA sequencing. The results indicated that melatonin regulated the expression of ABA and GA genes in the plant signal transduction pathway, induced embryo root development and seed germination, and alleviated dormancy. We found that the expression of the ABA signaling gene GhABF2 was up-regulated and GhDPBF2 was down-regulated, and the expression of GA signaling genes (e.g., GhGID1C and GhGID1B) was up-regulated by melatonin.Conclusions: We discovered that melatonin enhances salt tolerance in cotton seeds by regulating ABA and GA and by mediating the expression of hormone-related genes in plant hormone signal transduction. This should help us to explore the regulatory mechanisms of cotton resistance and provide a foundation for the cultivation of new varieties.

Retraction: Physiological Responses of Pea Plants to Salinity and Gibberellic Acid

“…In order to improve the performance of plants under saline stress, researchers have now turned their attention to the use of growth regulators, such as GA3, which play an important role in regulating the response of cotton plants to the external environment and in controlling gene expression under saline stress [6]. Reduced plant growth under drought or salinity may be due, at least in part, to reduced gibberellin production or the inability of plants to respond to this hormone [7].…”

Exogenous melatonin induces tolerance to drought stress damage in seedlings and soybean plants

“…Under drought and salt stresses during seed germination, starch hydrolysis is inhibited, making it difficult to supply large amounts of nutrients to the seeds, thus inhibiting seed germination. In cotton seeds germination, ML promoted α-amylase and β-amylase activity under osmotic stress, promoting the germination (Chen et al, 2021), and exogenous ML increased biomass and leaf area of maize seedlings under drought stress (Wei et al, 2014), demonstrating alternative mechanisms of action for the seed to germinate under stressful conditions.…”

Application of melatonin-mediated modulation of drought tolerance by regulating photosynthetic efficiency, chloroplast ultrastructure, and endogenous hormones in maize

“…Therefore, numerous studies have been undertaken to enhance crop tolerance and mitigate the negative impact of various abiotic stresses, including drought stress. However, the exogenous application of plant hormones plays a crucial and even decisive role in regulating plant growth and development [9].…”

“…Melatonin treatment up-regulates the expression of critical genes involved in GA 3 biosynthesis. It down-regulates critical genes involved in ABA biosynthesis to promote the use of nutrients, synthesize new proteins, and increase Limonium bicolor seeds' germination under abiotic stress conditions [9,28]. Melatonin is a plant growth hormone that is closely related to auxin [29].…”