Melatonin enhances salt stress tolerance in rubber tree (Hevea brasiliensis) seedlings.

• Melatonin improve rubber tree seedlings tolerance to salt stress. • Melatonin enhance salt stress tolerance directly or indirectly by counteracting H 2 O 2 accumulation in rubber tree. • Melatonin enhances salt tolerance by regulating the genes involved in photosynthesis, ROS metabolism, flavonoids and melatonin biosynthesis to counteract the cellular accumulation of H 2 O 2 in rubber tree. As a well-known agent, melatonin plays very important roles in animals. However, its possible function is less clear in plants, especially in rubber tree. In this study, we demonstrate that melatonin acts as a potential agent to enhance salt stress tolerance in rubber tree seedlings. Chlorophyll degradation and H 2 O 2 accumulation in leaves of seedlings under salinity stress were significantly relieved by melatonin treatment. Transcriptome analyses suggested that melatonin was a potential antioxidant, and its exogenous application resulted in enhanced antioxidant protection mainly by regulating the genes involved in photosynthesis, ROS metabolism, flavonoids and melatonin biosynthesis. These results demonstrate that melatonin can enhance salt stress tolerance directly or indirectly by counteracting the cellular accumulation of H 2 O 2 in rubber tree. Our findings are helpful for not only understanding melatonin's roles in salinity stress, but also providing new insights into potential utilization of melatonin against abiotic stresses in rubber tree. [ABSTRACT FROM AUTHOR]