D-Root: a system for cultivating plants with the roots indarkness or under different light conditions

Abstract

In nature roots grow in the dark and away from light (negative phototropism). However, most currentresearch in root biology has been carried out with the root system grown in the presence of light. Here, wehave engineered a device, called Dark-Root (D-Root), to grow plants in vitro with the aerial part exposed tothe normal light/dark photoperiod while the roots are in the dark or exposed to specific wavelengths orlight intensities. D-Root provides an efficient system for cultivating a large number of seedlings and easilycharacterizing root architecture in the dark. At the morphological level, root illumination shortens rootlength and promotes early emergence of lateral roots, therefore inducing expansion of the root system. Sur-prisingly, root illumination also affects shoot development, including flowering time. Our analyses alsoshow that root illumination alters the proper response to hormones or abiotic stress (e.g. salt or osmoticstress) and nutrient starvation, enhancing inhibition of root growth. In conclusion, D-Root provides a grow-ing system closer to the natural one for assaying Arabidopsis plants, and therefore its use will contribute toa better understanding of the mechanisms involved in root development, hormonal signaling and stressresponses.