Novel root culture system using a recessive mutant with a rooty phenotype

Hairy roots induced by Agrobacterium rhizogenes-mediated transformation are widely used for the study of metabolic regulation and large-scale metabolite production. We developed an alternative root culture using an allelic mutant of Arabidopsis superroot 1 (sur1). When the mutant was cultured in liquid modified Heller's medium developed for hairy root cultures, it grew rapidly into a globe-shaped rooty phenotype and was easily subcultured in the medium. This mutant is advantageous as the desired characteristics can likely be maintained via seeds because the rooty phenotype is recessive. To verify this postulate, heterozygous sur1 plants were crossed with fatty acid desaturase ( fad) mutants. The sur1 homozygous mutants under fad2 and fad3 background accumulated high amounts of oleic acid and linolenic acid, respectively, and the mutant crossed with a FAD3 overexpression transformant accumulated high amounts of a -linolenic acid. Thus, the sur1 root culture system is an alternative tool for studying metabolic regulation and the production of useful compounds in roots.