Selenium: A Game Changer in Plant Development, Growth, and Stress Tolerance, via the Modulation in Gene Expression and Secondary Metabolite Biosynthesis

Abstract

The presence of selenium (Se) is not widely established as crucial for crops, although it is commonly recognized as an important nutrient for animals as well as humans. Even so, it is inevitably accepted that Se usually contributes positively to the life cycle of plants. Previous findings suggested that small amounts of Se seem to have a produc-tive role in growth and production. As a result, Se is assumed to function in multiple ways, primarily by influen-cing a variety of biochemical and physiological functions. Also, Se also acts as a plant antioxidant and pro-oxidant and confers tolerance against different abiotic stresses, including salinity, drought, extreme temperature, and toxic metals/metalloids stresses. It reflects a defensive barrier against stress by increasing chlorophyll content synthesis, photosynthesis, oxygen supply, osmoprotectant concentration, and secondary metabolite acquisition. One other crucial role of Se is its ability to strengthen antioxidant performance in plants, thereby decreasing the concentration of reactive-oxygen-species (ROS). Furthermore, Se generates and modifies genes and proteins that respond situationally to stress, and the presence of high Se concentrations in the growth-medium can cause phytotoxic conditions via excessive ROS production, and through pro-oxidative Se occurrence, suppression of chlorophyll contents in the biosynthetic pathway, and the inhibition of plant developmental and normal physiological func-tions. Like a phytofortifier, the correct amount of Se can indeed enhance the nutrient quality of both crop and fodder production. Furthermore, crops have naturally developed ways to combat Se-deficiency and Se-toxicity. The current review focuses on recent advances in understanding the dynamics of Se, the positive and negative roles of Se in crop management, and its efficiency in countering abiotic stress.