Measurement of auxin transport in Arabidopsis thaliana

This protocol allows the measurement of auxin transport in roots, hypocotyls and inflorescences of Arabidopsis thaliana plants by examining transport of radiolabeled auxin or movement of an auxin-induced gene expression signal. The protocol contains four stages: seedling growth, auxin application, a transport period of variable length, and quantification of auxin movement or reporter expression. Beyond the time for plant growth, the transport assay can be completed within 4–18 h. Auxin is applied to seedlings in agar cylinders or droplets, which does not require specialized liquid-handling equipment or micromanipulators, in contrast with methods that apply auxin in liquid droplets. Spatial control of auxin application is reduced, but this method has the advantages of being technically more feasible for most laboratories and allowing agar containing radioactive auxin to be removed for pulse chase assays that determine transport rates. These methods allow investigation of genetic and environmental factors that control auxin transport.