# Understanding Crosstalk Between Phosphate and Immune-Related Signaling in Rice and Arabidopsis Through Live Imaging of Phosphate Levels

## TL;DR

This study uses a biosensor to track phosphate levels in living rice and Arabidopsis plants, revealing how phosphate signaling interacts with immune responses.

## Contribution

The study demonstrates FLIPPi's utility for real-time, in vivo phosphate monitoring and uncovers a link between phosphate and immune signaling in plants.

## Key findings

- FLIPPi accurately measures cytosolic phosphate levels in root epidermal cells of Arabidopsis and rice.
- Phosphate levels dynamically change in response to immune-related hormones and elicitors.
- Phosphite application disrupts phosphate accumulation in both species.

## Abstract

Phosphate (Pi) is a vital macronutrient for plant growth and development, and precise monitoring of its cellular dynamics is essential to understanding Pi homeostasis and its interaction with stress responses. Genetically encoded FRET-based biosensors such as FLIPPi enable real-time, non-invasive visualization of cytosolic Pi levels in living tissues. In this study, Arabidopsis and rice lines expressing a FLIPPi biosensor were used to monitor cytosolic Pi dynamics in root epidermal cells. Sensor functionality was confirmed by measuring FRET responses to graded Pi supplies, revealing a consistent reduction in FRET ratios with increasing Pi concentrations, reflecting elevated cytosolic Pi levels. Comparisons with a Pi-insensitive FLIPPi variant confirmed the specificity of the observed changes. Furthermore, live imaging demonstrated rapid and dynamic alterations in cytosolic Pi upon treatment with defense-related hormones and elicitors of immune responses supporting a link between Pi signaling and plant immunity. Finally, the application of phosphite, an analog of Pi, altered Pi dynamics in both Arabidopsis and rice, suggesting an interference with Pi accumulation. Collectively, our findings establish FLIPPi as a reliable tool for in vivo monitoring of Pi in Arabidopsis and rice plants, the model systems for studies in dicotyledonous and monocotyledonous species, respectively.