'Master regulator' protein controls flowering, disease resistance in plants

Feb 05, 2014 by Natalie Van Hoose

(Phys.org) —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 shows.

"MED18 is like a master regulator," said Tesfaye Mengiste, professor of botany and 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 and vegetables than any other disease.

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. 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 in Arabidopsis plants infected with fungus.

"This provides a new hope for resisting fungal infections because MED18 functions differently than more classical defense tactics," Mengiste said.

Using MED18 to toughen up plants' defense against would not necessarily require generating transgenic plants, said Mengiste. Natural variants with desirable characteristics could also 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 is also 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 ."

Explore further: How an aggressive fungal pathogen causes mold in fruits and vegetables

More information: "MED18 interaction with distinct transcription factors regulates multiple plant functions." Zhibing Lai, Craig M. Schluttenhofer, Ketaki Bhide, Jacob Shreve, Jyothi Thimmapuram, Sang Yeol Lee, Dae-Jin Yun,Tesfaye Mengiste. Nature Communications 5, Article number: 3064 DOI: 10.1038/ncomms4064
Received 13 August 2013 Accepted 04 December 2013 Published 23 January 2014

Abstract
Mediator is an evolutionarily conserved transcriptional regulatory complex. Mechanisms of Mediator function are poorly understood. Here we show that Arabidopsis MED18 is a multifunctional protein regulating plant immunity, flowering time and responses to hormones through interactions with distinct transcriptional factors. MED18 interacts with YIN YANG1 to suppress disease susceptibility genes glutaredoxins GRX480, GRXS13 and thioredoxin TRX-h5. Consequently, yy1 and med18 mutants exhibit deregulated expression of these genes and enhanced susceptibility to fungal infection. In addition, MED18 interacts with ABA INSENSITIVE 4 and SUPPRESSOR OF FRIGIDA4 to regulate abscisic acid (ABA) responses and flowering time, respectively. MED18 associates with the promoter, coding and terminator regions of target genes suggesting its function in transcription initiation, elongation and termination. Notably, RNA polymerase II occupancy and histone H3 lysine tri-methylation of target genes are affected in the med18 mutant, reinforcing MED18 function in different mechanisms of transcriptional control. Overall, MED18 conveys distinct cues to engender transcription underpinning plant responses.

Related Stories

Sniffed out: The 'gas detectors' of the plant world

Jan 23, 2014

The elusive trigger that allows plants to 'see' the gas nitric oxide (NO), an important signalling molecule, has been tracked down by scientists at The University of Nottingham. It is the first time that a central mechanism ...

Recommended for you

Chrono, the last piece of the circadian clock puzzle?

11 hours ago

All organisms, from mammals to fungi, have daily cycles controlled by a tightly regulated internal clock, called the circadian clock. The whole-body circadian clock, influenced by the exposure to light, dictates the wake-sleep ...

Drought hormones measured

12 hours ago

Floods and droughts are increasingly in the news, and climate experts say their frequency will only go up in the future. As such, it is crucial for scientists to learn more about how these extreme events affect plants in ...

Research traces the genetic print of the Asturian people

19 hours ago

The DNA of the people of Asturias still maintains the genetic prints of remote ages. A research conducted at the University of Oviedo proves that the old frontiers marked by the pre-Roman Astur settlements have left their ...

User comments : 0

More news stories

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.