Growth and Luminescence Observatory for Roots (GLO-Roots): A Platform for the Analysis of Root Structure and Physiology in Soil

The identification of roots traits that enable plant  growth in poor soils is key to provide crops with good yields and nutritional quality. However roots are buried deep in  soil and difficult to sample or image without altering their basic structure and physiology. In order to understand and image the basic processes occurring in roots researchers have to make compromises and study roots in rather unrealistic experimental growth environments. In an effort to understand Arabidopsis root biology in more realistic conditions (no sterile, transpiring environment, roots grown in dark etc.) we have developed a new growth and imaging system that enables the simultaneous observation of root growth, physiology and gene expression patterns of roots of plants growing in soil, in a transpiring environment and for extended periods of time. The system is based on the use of bioluminescent reporters emitting at different wavelengths of light. We use single color transgenic plants constitutively expressing one luciferase reporter to mark root architecture and double transgenic plants co-expressing another -different- luciferase reporter that marks genes responding developmental or physiological stimuli. We  grow the luciferase expressing plants in plastic vessels (rhizotrons) filled with soil and image them using a custom system that allows for the distinction of the different luciferases emission spectra. I will present data on how we are using the system to study the differences in root system architecture of different mutants and ecotypes and to understand root-microbe colonization processes.