East Lansing, Michigan
May 26, 2009
Michigan State University plant scientists have identified
two new genes and two new enzymes in tomato plants; those
findings led them to discover that the plants were making
monoterpenes, compounds that help give tomato leaves their
distinctive smell, in a way that flies in the face of accepted
thought.
Such research could help researchers find new ways to protect
plants from pests.
Based on years of research, scientists thought that plants
always used a specific compound, geranyl diphosphate, to make
monoterpenes. But MSU biochemistry and molecular biology
scientists Anthony Schilmiller and Rob Last were part of a
research team that has found that tomato plants use a different
compound, neryl diphosphate, as the substrate for making
monoterpenes. The difference is subtle, but the discovery will
change the way terpene (compounds that are responsible for the
taste and smell of many plants) research is done. The research
is published in the May 25 issue of the Proceedings of the
National Academy of Sciences.
"Essentially, this work subverts the dominant paradigm about an
important and widespread pathway in plants," Last explained.
"For years it was known that monoterpenes are made in a specific
way. But there were cases where that pathway likely wasn't
involved, given the kinds of compounds found in specific plants.
We showed that in tomato trichomes (small hair cells located
mainly on the plant's leaves and stems), the established pathway
is wrong. In the tomato trichome, two enzymes work together to
make the monoterpenes in a previously unsuspected way."
The two newly identified genes, neryl diphosphate synthase 1
(NDPS1) and phellandrene synthase 1 (PHS1), cause the tomato
plant to make the new enzymes that produce the monoterpenes.
As the team was sequencing the DNA of tomato trichomes,
Schilmiller and Eran Pichersky, of the University of Michigan,
noticed that there were many sequences from genes that weren't
supposed to be involved in monoterpene production. Because the
sequences were found so frequently, they hypothesized the genes
must be making high levels of compounds in the trichome.
"We had to think outside the box to figure out what the function
of NDPS1 and PHS1 were," Schilmiller said. "Our colleagues at
the University of Michigan, Eran Pichersky and Ines
Schauvinhold, were instrumental in coming up with theories and
running the assays."
Terpenes are the largest class of molecules made by plants –
tens of thousands of different terpenes have been identified.
Some of the known functions of terpenes include attracting
pollinators, repelling pests and protecting the plant from
diseases, as well as giving many plants their smell and taste.
The aroma of many leaf spices, such as mint and basil, come from
terpenes.
These new discoveries will allow other scientists to look for
similar genes in other plants and perhaps discover new enzymes
that make monoterpenes, which could lead to new ways to protect
plants from pests.
Other co-authors from MSU are Amanda Charbonneau,
biochemistry and molecular biology research assistant; and
Matthew Larson and Curtis Wilkerson, of the bioinformatics core
of the Research Technology Support Facility; from U-M are Adam
Schmidt and Richard Xu.
This research is funded by the National Science Foundation.
Last's research also is supported by the Michigan Agricultural
Experiment Station.
Michigan State University has been advancing knowledge and
transforming lives through innovative teaching, research and
outreach for more than 150 years. MSU is known internationally
as a major public university with global reach and extraordinary
impact. Its 17 degree-granting colleges attract scholars
worldwide who are interested in combining education with
practical problem solving. |
|