Serine Metabolic Networks in Plants

Abstract

The amino acid L-serine (Ser) is indispensable for several cellular processes. In addition to forming part of proteins, Ser is required for the synthesis of other amino acids, nitrogen bases, and lipids and is a source of one-carbon units (1C) for methylation reactions. Unlike animals, plants synthesize Ser through different pathways, which has complicated the understanding of the amino acid homeostasis. Three Ser biosynthesis pathways have been described in plants: the glycolate pathway, associated with photorespiration, and two non-photorespiratory pathways, the phosphorylated and the glycerate pathway of Ser biosynthesis. In recent years, the specific contribution of each pathway to Ser homeostasis and how they are coordinated to participate in plant metabolism and development have started to be elucidated. Current knowledge on serine biosynthesis and functions in plants is reviewed here and, whenever possible, compared with current knowledge in mammals. We focus on recent advances that link Ser with other metabolic processes, such as the Ser-glycine-1C network, and nitrogen and sulfur metabolism. We also discuss the role of Ser metabolic reprogramming in the plant response to biotic and abiotic stresses and how it can be affected by climate change.