Amino acid sensing and signaling in plants

Amino acids are central metabolic intermediates but they can also serve as metabolic signals conveying information on nutrient status, developmental state, and environmental conditions. This review summarizes current concepts and emerging mechanisms of amino acid sensing and signaling in plants. Recent progress has expanded our understanding of glutamate receptor–like channels (GLRs), which couple amino acid perception to Ca 2+ signaling during root growth, wound responses and immunity. Plant-specific upstream regulators of the target of rapamycin (TOR) kinase complex have been identified that link amino acid sensing to growth control. New findings provide insight into tissue-specific functions of TOR as well as its integration with hormone signaling and amino acid metabolism. In addition, we discuss cysteine-dependent protein persulfidation as a post-translational modification integrating sulfur metabolism and redox regulation. Despite recent progress, mechanistic knowledge on amino acid signaling processes in plants is far from complete and the distinct metabolic context of autotrophy suggests that additional, potentially plant-specific sensing principles remain to be uncovered.