WEST LAFAYETTE, Ind. — The next time you stop and smell the
roses, thank MED18.
The protein MED18 controls many important plant processes,
including when a plant blossoms, how it resists key fungal diseases, and how it
responds to environmental stress factors, a Purdue University study
“MED18 is like a master regulator,” said Tesfaye Mengiste,
professor of botany and plant pathology and the study’s lead researcher. “The
versatility of its functions is surprising.”
Understanding and manipulating MED18 could lead to improved
resistance to necrotrophic fungal diseases in plants, Mengiste said.
Necrotrophs are fungi that infect and kill plant cells to
take their nutrients, causing diseases that are difficult and costly to manage.
Examples include northern leaf blight, ear rot and gray mold, which is estimated
to cause a greater economic loss of ornamental plants and vegetables than any
When necrotrophs attack, they stimulate an increase in the
expression of two plant genes that render a plant more susceptible to infection.
But MED18 works with other proteins to “turn off” those target genes,
contributing to disease resistance in an indirect yet important way, Mengiste
MED18 also helps activate a gene that bolsters a plant’s
defense against wounding and infection by necrotrophs.
Mengiste and his fellow researchers found that the presence
of MED18 limited disease symptoms and fungal growth in Arabidopsis plants
infected with gray mold fungus.
“This provides a new hope for resisting fungal infections
because MED18 functions differently than more classical defense tactics,” he
Using MED18 to toughen up plants’ defense against fungal
diseases would not necessarily require generating transgenic plants, Mengiste
said. Natural variants with desirable characteristics also could be used to
cultivate more disease-resistant specimens in plant populations.
The study showed that MED18 plays a vital role in other
plant functions as well, including flowering time and how a plant responds to
abscisic acid, a hormone that regulates how plants cope with environment
stresses such as drought.
The protein also is involved in starting, guiding and
terminating transcription, impacting multiple steps of gene expression. Mengiste
compares MED18’s role in transcription with that of an orchestra conductor who
begins the music, signals the entrance of certain instruments and draws the
piece to a close.
The variability of the protein’s functions makes it a prime
target for genetic improvement of plants, he said.
“Now that we know what it does, we can use MED18 to improve
crop growth, fruit production, flowering time and disease resistance,” he
The paper was published in Nature Communications and is available at
The National Science Foundation and the Next-Generation
BioGreen 21 Program provided funding for the research.