Journal Article

Melatonin increases growth and salt tolerance of Limonium bicolor by improving photosynthetic and antioxidant capacity

Xu, Hualing, Li, Junpeng, Zhang, Mingjing, Chen, Min, Ning, Kai, Liu, Yun, Wang, Baoshan

2022

Overview

Background Soil salinization is becoming an increasingly serious problem worldwide, resulting in cultivated land loss and desertification, as well as having a serious impact on agriculture and the economy. The indoleamine melatonin (N-acetyl-5-methoxytryptamine) has a wide array of biological roles in plants, including acting as an auxin analog and an antioxidant. Previous studies have shown that exogenous melatonin application alleviates the salt-induced growth inhibition in non-halophyte plants; however, to our knowledge, melatonin effects have not been examined on halophytes, and it is unclear whether melatonin provides similar protection to salt-exposed halophytic plants. Results We exposed the halophyte Limonium bicolor to salt stress (300 mM) and concomitantly treated the plants with 5 μM melatonin to examine the effect of melatonin on salt tolerance. Exogenous melatonin treatment promoted the growth of L. bicolor under salt stress, as reflected by increasing its fresh weight and leaf area. This increased growth was caused by an increase in net photosynthetic rate and water use efficiency. Treatment of salt-stressed L. bicolor seedlings with 5 μM melatonin also enhanced the activities of antioxidants (superoxide dismutase [SOD], peroxidase [POD], catalase [CAT], and ascorbate peroxidase [APX]), while significantly decreasing the contents of hydrogen peroxide (H 2 O 2 ), superoxide anion (O 2 •− ), and malondialdehyde (MDA). To screen for L. bicolor genes involved in the above physiological processes, high-throughput RNA sequencing was conducted. A gene ontology enrichment analysis indicated that genes related to photosynthesis, reactive oxygen species scavenging, the auxin-dependent signaling pathway and mitogen-activated protein kinase ( MAPK ) were highly expressed under melatonin treatment. These data indicated that melatonin improved photosynthesis, decreased reactive oxygen species (ROS) and activated MAPK-mediated antioxidant responses, triggering a downstream MAPK cascade that upregulated the expression of antioxidant-related genes. Thus, melatonin improves the salt tolerance of L. bicolor by increasing photosynthesis and improving cellular redox homeostasis under salt stress. Conclusions Our results showed that melatonin can upregulate the expression of genes related to photosynthesis, reactive oxygen species scavenging and mitogen-activated protein kinase ( MAPK ) of L. bicolor under salt stress, which can improve photosynthesis and antioxidant enzyme activities. Thus melatonin can promote the growth of the species and maintain the homeostasis of reactive oxygen species to alleviate salt stress.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Abiotic stress / agricultural land / Agriculture / Analysis / Antioxidant / antioxidant activity / antioxidant enzymes / Antioxidants / Antioxidants - metabolism / ascorbate peroxidase / Ascorbic acid / Auxins / Biomedical and Life Sciences / Catalase / Cultivated lands / Desertification / Environmental aspects / Enzymatic activity / Enzymes / Gene expression / Gene Expression Regulation, Plant - drug effects / gene ontology / Gene sequencing / Genes / Growth / growth retardation / Halophytes / Homeostasis / Hydrogen peroxide / Identification and classification / Impact analysis / Kinases / L-Ascorbate peroxidase / Lavenders / Leaf area / Life Sciences / Limonium / Limonium bicolor / Malondialdehyde / MAP kinase / Measurement / Melatonin / Melatonin - pharmacology / mitogen-activated protein kinase / Oxidative stress / Oxygen / Oxygen enrichment / Peroxidase / Photosynthesis / Photosynthesis - drug effects / Physiological aspects / Plant growth / Plant resistance / Plant Sciences / Plumbaginaceae - drug effects / Plumbaginaceae - genetics / Plumbaginaceae - growth & development / Plumbaginaceae - metabolism / Protein kinase / Protein synthesis / Proteins / Reactive oxygen species / Reactive Oxygen Species - metabolism / RNA / RNA sequencing / Salinity tolerance / Salinization / Salt / Salt Stress / Salt stress (Botany) / Salt tolerance / Salt Tolerance - drug effects / Scavenging / Seedlings / Signal transduction / Soil salinity / soil salinization / Soils, Salts in / superoxide anion / Superoxide anions / Superoxide dismutase / Tree Biology / Water use / Water use efficiency