ABSTRACT
Although amino acids primarily serve as the building blocks of proteins, in plants amino acids also serve as important alternative energy substrates, particularly when plants are exposed to stresses that cause energy deprivation. The contribution of amino acids to energy homeostasis in response to stress occurs through their catabolism, which funnels their carbon backbones into the tricarboxylic acid (TCA) cycle, providing an alternative source of electrons for the mitochondrial electron transport chain. As such, amino acid catabolism, which also includes the association of the amino acid Glu and the γ-aminobutyric acid (GABA) shunt, is becoming recognized as a critical element of energy metabolism in stress and carbon starvation. In the first part of the present review, we focus on recent findings concerning modes of action of amino acid catabolism as an alternative source of energy in stress conditions. Second, we reveal how systems biology approaches, including gene coexpression analysis and transcript and metabolic profiling, led to the discovery of new biological processes associating plant amino-acid (AA) metabolism with response and adaptation to stress.
