Spatiotemporal visualization of SnRK1 activity unveils its multifaceted role during plant growth and development

Plants are able to endure fluctuating environments through complex signaling networks, meticulously balancing growth decisions based on internal and external cues. Central to these networks, Sucrose non-fermenting-1 related kinase 1 (SnRK1) acts as a molecular fuel gauge that promotes survival by restraining growth and favoring catabolism under restrictive conditions. However, the detailed spatiotemporal dynamics of SnRK1's regulation of plant growth remain poorly understood given the lack of adequate tools that can capture these dynamics at cellular resolution. In this study, we employed a separation of phase-based activity reporter of kinase (SPARK)-based sensor to monitor SnRK1 activity at cellular resolution during the plant life cycle. Our findings unveiled a dual role for SnRK1: a constitutive one, tightly linked to meristematic and vascular tissues, and a dynamic one, steering growth according to energy and nutrient availability. Real-time visualization of a growing Arabidopsis root corroborated this dual role, showing SnRK1’s essential role in maintaining the apical root meristem, while also dynamically steering circadian root growth. Applying CRISPR-based tissue-specific knockout (CRISPR-TSKO) of SnRK1, confirmed SnRK1’s pivotal function in root growth and development. Our results highlight the power of ASP-SPARK for real-time, in vivo analysis of SnRK1 activity, advancing our understanding of this key metabolic regulator and paving the way for detailed insights into its relationship with plant growth and stress responses.