Melatonin enhances the tolerance to iron deficiency stress through scavenging ROS in apple

Abstract

Iron (Fe) is an essential micronutrient for plants. Fe deficiency, resulting from poor availability induced by its insolubility in most soils, severely affects the growth and yield of apple (Malus domestica Borkh.). Except for the application of an Fe nutrition agent, there is a lack of efficient and environmently-friendly ways to relieve plants from Fe deficiency in a modern orchard. Here, we observed that melatonin (MT), as an efficient reactive oxygen species (ROS) scavenger, could alleviate the chlorosis of leaves in apple under Fe deficiency, following increased Fe content, decreased chlorophyll degradation and stable photosynthetic rate. Exogenous melatonin induced the synthesis of endogenous melatonin and improved the activities of antioxidant enzymes, which decreased the oxidative damage induced by Fe deficiency through properly scavenging O2•− and H2O2. In addition, exogenous melatonin promoted the expression of its synthetase genes, but decreased their protein level, inferring post-transcriptional regulation. In brief, melatonin improved the tolerance to Fe deficiency through ROS migration and chloroplast protection in apple. This work uncovered the role of melatonin on Fe deficiency tolerance and also provided a potential way to relieve plants from Fe deficiency stress for apple production.