FoodProductionDaily.com, France
10-04-07
Hairy roots eyed as flavour factories
By Stephen Daniells
Hairy roots, structures formed by a common soil bacterium after it 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