Hairy roots eyed as flavour factories
infects a plant, could be tailored to become natural factories to
produce food flavourings, researchers have reported.
Researchers from Rice University, the University of Minnesota, and Iowa State University consider the potential of the hairy root line of transgenic periwinkle (Catharanthus roseus) to produce value-added secondary metabolites, like food flavourings or pharmaceuticals. The research could lead to the production of hairy root factories, churning out these value-added secondary metabolites. Hairy root is a plant disease caused when a common soil bacterium infects a plant by transferring its DNA into the cells of the host plant, which then becomes integrated into the nuclear genome. Eventually, the host plant develops a system of fuzzy roots near the site of the infection. These 'hairy roots' grow rapidly and differentiate, and result in the stable and extensive production of secondary metabolites. By inserting a specific gene into the bacterium, researchers can integrate that gene into the host's DNA. The study, scheduled for publication in the November/December issue of Biotechnology Progress, indicates that these hairy roots can be grown in cell cultures that churn out the product of the inserted gene, whether that's a flavour or a natural-product based, with a stability and productivity not possible with most other plant cell cultures. Lead researcher Ka-Yiu San and colleagues set about determining the long-term stability of genetically-altered roots, and report the maintenance of growth of a transgenic hairy root culture for more than 4.5 years. They infected a species of periwinkle with a hairy root bacterium carrying a gene encoding a fluorescent protein, generating hairy roots containing the fluorescent protein. The root tips were then transferred into fresh liquid every four weeks, creating a root culture that was genetically stable throughout that period, glowing appropriately in response to a special chemical signal, reported San. "This study shows that a transgenic hairy root line can be stably maintained for over four years while retaining the activity of the inserted gene of interest," wrote the researchers. "This observation has important implications for the use of hairy root cultures in industrial applications," they concluded. Despite concerns in various countries, particularly Europe, about genetically modified organisms (GMOs), it is currently unclear and debatable whether the flavourings would be classed as a GM ingredient. Source: Biotechnology Progress Published on-line ahead of print, doi: 10.1021/bp0702166 "Long-term Maintenance of a Transgenic Catharanthus roseus Hairy Root Line" Authors: C.A.M. Peebles, S.I. Gibson, J.V. Shanks, and K.-Y. San
