Novel micro-phenotyping approach to chemical genetic screening for increased plant tolerance to abiotic stress

Studying the effects of small molecules on root system development in the context of a large-scale chemical genetic screen has previously been a technical challenge. The recent development of novel seedling growth devices (“Phytostrips”), used in combination with standard 96-well microtiter plates, has made it possible to perform detailed studies of changes in root morphology and root system architecture following the application of a library of chemical compounds. Phytostrips were originally designed to allow automated robotic capture of images of roots and shoots of the model species Arabidopsis thaliana, but can also be used for manual screens that are more laborious but do not require the investment in expensive robotics. Here we describe a protocol for the use of Phytostrips to perform chemical genetic screens that rely on clearly observable changes in root morphology or root system architecture. As an example, we describe the use of polyethylene glycol to impose an abiotic stress related to reduced water potential and the application of a chemical screen for small molecules that are able to rescue Arabidopsis root development from the disruptive effect of the polyethylene glycol treatment. The protocol we describe provides a template for the application of a multiplicity of other screens for compounds that can antagonize the effects of a range of abiotic stresses on root development