Melatonin plays a pivotal role in conferring tolerance against endoplasmic reticulum stress via mitogen-activated protein kinases and bZIP60 in Arabidopsis thaliana

Abstract

Melatonin has diverse roles as a signaling molecule that activates a number of downstream defense systems against various biotic and abiotic stresses in plants. However, there have been no reports regarding a direct protective role of melatonin against endoplasmic reticulum (ER) stress. Here, we report that exogenous melatonin treatment attenuated ER stress damage by preserving ER structure and enhancing secretory protein folding capacity in response to tunicamycin treatment. Further transgenic experiments indicated that melatonin-deficient snat1 mutant was hypersensitive to ER stress, whereas melatonin-proficient SNAT1 overexpression (OE) was tolerant to ER stress, as evidenced by reduced ion leakage and higher transcript levels of ER chaperones, including luminal binding protein (BIP) 2, BIP3, and CNX1, compared to wild-type controls. Moreover, this melatonin-mediated ER stress tolerance was dependent on the bZIP60 transcription factor and mitogen-activated protein kinase. Our data suggest that melatonin is actively involved in maintaining homeostasis of the ER during normal plant growth, and also has a protective effect against many environmental stressors that induce ER stress.