Calcium-dependent protein kinases (CDPKs) play essential roles in plant development and stress responses. CDPKs have a conserved kinase domain, followed by an auto-inhibitory junction connected to the calmodulin-like domain that binds Ca 2+. These structural features allow CDPKs to decode the dynamic changes in cytoplasmic Ca 2+ concentrations triggered by hormones, biotic and abiotic stress. In response to these signals, CDPKs phosphorylates downstream protein targets to regulate growth and stress responses according to the environmental and developmental settings. The latest advances in the understanding of metabolic, transcriptional, and protein-protein interaction networks involving CDPKs suggest their direct influence on plant carbon/nitrogen (C/N) balance. Here, we discuss how CDPKs could be key signaling nodes connecting stress responses with metabolic homeostasis, acting together with the sugar and nutrient signaling hubs SnRK1, HXK1, and TOR to improve plant fitness.

Plants rely on the carbon fixed by photosynthesis into sugars to grow and reproduce. However, plants often face non-ideal conditions caused by biotic and abiotic stresses. These constraints impose challenges to managing sugars, the most valuable plant asset. Hence, the precise management of sugars is crucial to avoid starvation under adverse conditions and sustain growth. This review explores the role of post-translational modifications (PTMs) in the modulation of carbon metabolism. PTMs consist of chemical modifications of proteins that change protein properties, including protein-protein interaction preferences, enzymatic activity, stability, and subcellular localization. We provide a holistic view of how PTMs tune resource distribution among different physiological processes to optimize plant fitness.