Hairy roots as a tool for the functional analysis of plant genes

Abstract

With its root-inducing (Ri) plasmid, Agrobacterium rhizogenes is a valuable alternative to transfer gene constructs into the genome of plant species which are difficult to stably transform with disarmed strains of Agrobacterium tumefaciens. Composite plants consisting of transformed hairy roots induced on a non-transgenic shoot have been reported in an increasing number of legume and nonlegume plant species. They were first used in the model legumes Medicago truncatula and Lotus japonicus to study the symbiotic interaction with rhizobia. Since then, composite plants have been shown to be effective to investigate the function of genes involved in mycorrhizal symbiosis, root-nematode and rootpathogen interactions, resistance response of plant roots to parasitic weeds, root development and branching, and the formation of wood. The different methodologies developed to generate composite plants and the applications of co-transformed hairy roots for studying gene function are discussed in this chapter, together with recent opportunities offered by genome editing technologies in hairy roots.