Studies of Secondary Metabolic Pathways in Transformed Roots

The properties of transformed lines generally reflect those of normal roots but there are some differences. Transformed roots are morphologically different from normal plant roots in that they are much more highly branched. Root cultures have proved ideal for feeding experiments since relatively high quantities of roots can be fed under sterile conditions with precursors or inhibitors and the effects on the pathway evaluated. The transferred genes involved in hairy root formation include genes leading to the production in the plant of specific bacterial metabolites — the opines — and genes which encode enzymes that promote the hydrolysis of conjugated forms of the plant hormones. Feeding metabolic precursors to hairy roots in attempts to increase the formation of end-products has in general produced unremarkable results. The advantage of hairy root cultures for enzymological studies lies principally and obviously in the ease of generating relatively abundant quantities of sterile, rapidly-growing tissue under defined conditions.