www.czu.cz ; www.raupp.info

Just one cellular pathway produces the raw ingredients plants use to make
thousands of compounds, from molecules with anticancer properties to the
active ingredient in catnip, according to a team of researchers at Purdue
University and the Max Planck Institute for Chemical Ecology, January 2005.

This finding challenges long-held assumptions about how plants produce
these commercially important products. The research also could have
important implications for researchers trying to harness plant pathways to
produce essential oils, often used as flavor additives in food and medicine
or as fragrance in body-care products, said Natalia Dudareva, professor of
horticulture and lead researcher of the study.

"Our research has applications in the future metabolic engineering of
essential oil production," Dudareva said. "The yield of these compounds
depends on the amount of materials available in the cell, and knowing where
these compounds come from and which pathway produces them is the place to
start."

Dudareva and her colleagues report in the current issue (Tuesday, Jan. 18)
of Proceedings of the National Academy of Science that the molecular
precursors to a group of compounds called terpenoids - the largest and most
diverse family of natural products - come from a single plant pathway,
located inside the same part of a cell where photosynthesis occurs.

Terpenoids are made from compounds called precursor molecules, which are a
kind of molecular raw material. Just as a potter can transform five
identical spheres of clay into five unique pieces of art, identical
precursor molecules can transform into unique compounds by following
different molecular pathways.

Scientists previously discovered that two independent pathways, located in
different compartments within a plant cell, use these precursor molecules to
produce terpenoids. Most scientists assumed that both pathways were capable
of producing these precursor molecules as well.

The discovery that only one pathway produces these precursors is a
significant breakthrough, Dudareva said.

"We never expected to find this," she said. "This is the first time anyone
has realized that only one of the two available pathways operates to make
the precursor."

She also found that while some of the precursor molecules remain in the
compartment where they are made, some travel through the cell to another
compartment, where they enter a second pathway in terpenoid production.

The process can be likened to a manufacturing plant with an assembly line
that makes a car part, such as a steering wheel. Some of those steering
wheels remain on-site to be added to cars manufactured at that plant.
Additional steering wheels are transported to another plant that, instead of
making its own steering wheels, uses those from the first plant to produce
its product.

Just as delivering steering wheels from one manufacturing facility to
another requires some kind of transportation, molecules also rely on
vehicles to travel around the interior of a cell. Exactly how the precursor
molecules in this system travel from one compartment to another, however,
remains a mystery.

"This work hints at the existence of a transporter to carry precursor
molecules across the cell," said David Rhodes, Purdue professor of
horticulture and a collaborator on the paper. "We already know that plants
have a huge number of compartments that exchange materials. Now we need to
figure out how these compartments facilitate this one-way flow of precursor
molecule."

Dudareva used snapdragon flowers in this research, a model plant system she
also uses in her studies of floral scent regulation.

While limited to this one species, she suggests similar results might be
found in other plants.

"Others have previously shown indirectly that the same pathway that's not
functioning in snapdragons is also blocked in basil plants and in mint," she
said. "This opens the question of how widespread is this phenomenon?"

The finding also raises intriguing questions in plant evolution.

"We still don't understand why plants have duplicate pathways in different
parts of the cell," Rhodes said. "And if one of these pathways is not
operating, why haven't plants lost it over the course of evolution?"

Dudareva's collaborators also include Irina Orlova at Purdue University, as
well as Susanna Andersson, Nathalie Gatto, Michael Reichelt, Wilhelm Boland
and Jonathan Gershenzon at the Max Planck Institute for Chemical Ecology in
Jena, Germany. Funding was provided by The National Science Foundation, Fred
Gloeckner Foundation, German Academic Exchange Service and Max Planck
Society.

[news.uns.purdue.edu]

------------------------------------------
Posted to Phorum via PhorumMail