Bidirectional crosstalk between plant hormone signaling and metabolism

Among the diverse metabolites produced by plants, hormones play crucial roles in coordinating plant growth and development with environmental stress responses. They achieve this via the coordination of intricate and often ancient signaling networks. An important component of these networks is often the reprogramming of primary metabolism or in the case of stress responses, both primary and secondary metabolism. However, the interface between plant hormones and metabolism is only partially characterized. In this review, we summarize recent advances in phytohormone biology, focusing on both how hormone signaling influences metabolism and how metabolic states, in turn, modulate hormone signaling. We describe how the metabolic response to hormones and the responsiveness of hormones to metabolites are particularly well characterized for certain hormones but relatively poorly understood for others. Particular attention is given to defining a conceptual framework through which hormone-driven regulation of metabolism and metabolic regulation of hormone signaling can be understood as an integrated bidirectional network, with specific attention to recent mechanistic advances. Finally, we review current and emerging techniques that should allow us to deepen our understanding of the metabolite-to-hormone interface, which will not only provide greater insight into how plants coordinate various aspects of their life cycle but will also likely provide hints toward selecting breeding targets for crop improvement.