Abstract
Melatonin, a small molecular weight indoleamine molecule, is involved in various biological processes and responses to environmental cues in plants. However, its function in abiotic stress response and the underlying mechanisms is less clear. In this study, we investigated the effect of melatonin on wheat seedlings growth under salt stress condition. Exogenous melatonin pretreatment partially mitigated the salt-induced inhibition of whole-plant growth as judged from shoot dry weight, IAA content, leaf photosynthesis rate, maximum photochemistry efficiency of photosystem II, and chlorophyll. The mitigation was also observed in reduced accumulation of H2O2 in melatonin-pretreated wheat seedlings exposed to salt stress. Exogenous melatonin increased endogenous melatonin content by evaluating the levels of TaSNAT transcript, which encodes a key regulatory enzyme in the melatonin biosynthetic pathway. Furthermore, melatonin increased polyamine contents by accelerating the metabolic flow from the precursor amino acids arginine and methionine to polyamines; melatonin also decreased the degradation of salt-induced polyamines. Taken together, these results provide the evidence that melatonin mitigates salt stress mainly through its regulation on polyamine metabolism of wheat seedlings.
Highlights
Environmental problems such as global warming, drought, and salinity severely limit agricultural productivity in many parts of the world (Tester and Langridge, 2010)
To investigate whether melatonin affects the endogenous levels of indolyl-3-acetic acid (IAA), we measured the IAA content from pretreated-wheat seedlings
Salt stress significantly inhibited the IAA producing, whereas these adverse effects can be alleviated on wheat seedling pretreated with melatonin
Summary
Environmental problems such as global warming, drought, and salinity severely limit agricultural productivity in many parts of the world (Tester and Langridge, 2010). Each year there is a deterioration of 2 million hectare (about 1%) of the world agricultural lands because of salinity, leading to reduced or no plant productivity (Ke et al, 2016). Because of complexities and controversies that are coupled to genetically modified crops, these genes have few applications in actual agriculture practice (Tester and Langridge, 2010). An alternative strategy for enhancing stress tolerance and extending leaf longevity could lead to important agricultural applications
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