Ethylene Synthesis and Redox Homeostasis in Plants: Recent Advancement

Abstract

The life cycle of plants is regulated by ethylene in numerous ways, including adaptations to biotic and abiotic stimuli, flower growth, fruit ripening, senescence, and seed germination. As a result, it is crucial for interactions to the environment that directly affect a plant’s capacity for adaptability and reproduction. Major progress has been made in recent years in our knowledge of the molecular mechanisms controlling the synthesis and activity of ethylene. The gaseous plant hormone ethylene is produced via a straightforward two-step biosynthesis process. Despite the simplicity of this route, current molecular and genetic investigations have shown that ethylene production regulation is far more complex and takes place at various layers. The homeostasis of ethylene’s general precursor S-adenosyl-L-methionine (SAM), which is subject to transcriptional and post translational control of its synthesizing enzymes (SAM synthetase), as well as the metabolic flux through the nearby Yang cycle, are closely related to each other. Two specific enzymes, 1 aminocyclopropane-1-carboxylic (ACS) synthase and ACC oxidase, continue ethylene production from SAM (ACO). In order for plant electron transport cascades to function effectively, both the oxidized and reduced forms of electron carriers must be present simultaneously. This requirement is known as redox positioning, which entails the transfer of electrons to molecular oxygen from various places in the respiratory and photosynthetic electron transport chains. During the course of a plant’s lifetime, adverse environmental conditions like drought, high or low temperature, heavy metal stress, etc., cause the development of superoxide, which in turn gives rise to additional reactive oxygen species (ROS). Ascorbate, a further hydrophilic redox buffer produced by plant cells, shields the plants from oxidative stress. The redox homeostasis is also governed by sizable pools of antioxidants. Additionally, tocopherol is an effective scavenger of ROS like singlet oxygen because it is a liposoluble redox buffer. Additionally, proteinaceous thiol members, including the electron transporters and energy metabolism mediators phosphorylated (NADP) and non-phosphorylated (NAD+) coenzyme forms, interact with ROS, metabolize, and maintain redox homeostasis. Examples include thioredoxin, peroxiredoxin, and glutaredoxin. ACC synthase (ACS), ACC oxidase, and aminocyclopropane-1-carboxylic (ACC) synthase (ACO).This review focuses on important new findings and incorporates knowledge of ethylene production and redox homeostasis in several plant species.