Monitoring nutrients in plants with genetically encoded sensors: achievements and perspectives

Abstract

Understanding mechanisms of nutrient allocation in organisms requires precise knowledge of the spatiotemporal dynamics of small molecules in vivo. Genetically encoded sensors are powerful tools for studying nutrient distribution and dynamics, as they enable minimally-invasive monitoring of nutrient steady-state levels in situ. Numerous types of genetically encoded sensors for nutrients have been designed and applied in mammalian cells and fungi. However, to date, their application for visualizing changing nutrient levels in planta remain limited. Systematic sensor-based approaches could provide the quantitative, kinetic information on tissue-specific, cellular and subcellular distributions and dynamics of nutrients in situ that is needed for the development of theoretical nutrient flux models that form the basis for future crop engineering. Here, we review various approaches that can be used to measure nutrients in planta with an overview over conventional techniques, as well as genetically encoded sensors currently available for nutrient monitoring, and discuss their strengths and limitations. We provide a list of currently available sensors and summarize approaches for their application at the level of cellular compartments and organelles. When used in combination with bioassays on intact organisms and precise, yet destructive analytical methods, the spatiotemporal resolution of sensors offers the prospect of a holistic understanding of nutrient flux in plants.

Fluorescent Protein-Based Sensors for Detecting Essential Metal Ions across the Tree of Life

“…78,226 The numerous opportunities for applying genetically encoded sensors to plants were recently reviewed. 227 A challenge in using fluorescence to detect metals in plants is the high autofluorescence of plant tissues. Here, bioluminescence-based sensors (described further below) could be particularly useful, given that external light excitation can be avoided.…”

“…Applications of genetically encoded sensors in plants to monitor changes in nutrients also remain relatively limited. Besides several Ca 2+ sensors, the eCALWY sensor family was used to detect Zn 2+ fluctuations in plants, and both GEPII1.0 and GINKO2 were used to monitor K + transients in plants. , The numerous opportunities for applying genetically encoded sensors to plants were recently reviewed . A challenge in using fluorescence to detect metals in plants is the high autofluorescence of plant tissues.…”

Optimal photosynthesis requires a balanced diet of ions

“…First is the study of ion concentrations in the chloroplast, which could be revolutionized thanks to genetically encoded ion sensors, as suggested by the authors. Starting with the development of Ca 2+ sensors, now sensors for K + , Mg 2+ , Cl − , and other ions have been successfully tested in various organisms (Sadoine et al ., 2023). Sensors that function within the correct concentration range can be titrated and expressed in both WT and mutant plant cells, and they can then be targeted to the plastid stroma and thylakoid lumen.…”

Chloroplast ion homeostasis – what do we know and where should we go?

“…Starting with Ca 2+ substrates, the development has advanced tremendously. By now, K + , Mg 2+ , Cl − , and several other sensors have been successfully tested in various organisms (Sadoine et al ., 2023). Sensors functional within the right concentration range can be titrated and expressed in WT and mutant plant cells.…”