An automated minirhizotron system for in situ imaging of GFP expression in roots

Roots, as the hidden half of plants, are the main organ absorbing water and nutrients from the soil. Yet, research into plant roots has lagged behind investigations of aboveground plant organs due to the difficulty of continuous monitoring of phenotypic changes in root architecture underground in a non-destructive manner. In this study, we developed a novel minirhizotron system based on common components of the fluorescence microscope. We examined the possibility of a pilot system for imaging green fluorescent protein (GFP) expression in roots within rhizoslides and glass containers and tested different parameters in order to achieve the best fit for imaging. Our results demonstrate that imaging GFP expression in roots provides a clearer visualization of the root system, effectively increasing an observable number of roots by minimizing interference from the soil compared to RGB images. We further miniaturized the imaging system and integrated it into the minirhizotron. The developed fluorescence minirhizotron is fully automated, high-throughput, and non-invasive allowing us to detect clear, continuous, in situ GFP fluorescence in roots. It is applicable across a wide range of scenarios. Currently, our ongoing work focuses on producing stress-inducible GFP expression in transgenic tobacco lines to enable rapid and early detection of plants under stress in a non-destructive manner. This study could help in distinguishing the roots of different plants and provide a potential contribution to breeding plants or in developing agro-techniques to save water, increase nutrient uptake, and improve crop yields in the era of climate change.