Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Why Fruits Ripen and Flowers Die: Scientists Discover How Key Plant Hormone Is Triggered

12.02.2009
Best known for its effects on fruit ripening and flower fading, the gaseous plant hormone ethylene shortens the shelf life of many fruits and plants by putting their physiology on fast-forward.

In recent years, scientists learned a lot about the different components that transmit ethylene signals inside cells. But a central regulator of ethylene responses, a protein known as EIN2, resisted all their efforts.

Finally, after more than a decade of constant probing, a team of researchers led by Joseph Ecker, Ph.D., a professor in the Plant Biology laboratory and director of the Salk Institute Genomic Analysis Laboratory, successfully pinned down the elusive protein. Turns out, the presence of ethylene stabilizes the otherwise ephemeral EIN2 allowing it to gather up enough strength to pass on ethylene’s message.

Their findings, published in the Feb. 15, 2009 edition of the journal Genes and Development, are an important step toward defining EIN2’s role in growth and development and modifying key processes to improve agriculture, preventing crop losses due to ethylene related processes.

“Ethylene is involved in a wide variety of processes and we knew from genetic experiments that EIN2 is right at the center of ethylene signaling pathway, but for the longest time we were unable to figure out how it is regulated,” says Ecker. “Now that we know that EIN2 is negatively regulated by protein degradation, we can begin to understand how it triggers all these different ethylene responses in plants.”

All aspects of a plant’s life are influenced by ethylene: It induces seed germination and the so-called triple response in seedlings, which helps them to push past obstructions. It regulates root hair growth in general and nodulation in nitrogen-fixing legumes. It stimulates fruit ripening, floral fading and abscission, which allows plants to drop fruits, leaves and flowers. But it also protects against pathogens and environmental stress.

While ethylene’s power has been harnessed since the ancient Egyptians discovered that scoring figs hastens the ripening process, it also causes significant losses for florists, markets, suppliers and growers. A single rotting apple’s ethylene production will accelerate the ripening process in nearby apples causing them to spoil as well. Stress during shipping and handling increases ethylene production in cut flowers inducing premature floral fading.

“Ethylene plays a big role in our daily life and ethylene overproduction causes huge economic losses every year,” says first author Hong Qiao, Ph.D., a postdoctoral fellow in Ecker’s lab. “Once we fill in the gaps in our understanding of the ethylene signaling pathway, we can use this knowledge to improve pathogen or drought resistance in plants.”

In the absence of ethylene, a protein called CTR1—short for constitutive triple response 1—shuts down the ethylene pathway through the repression of a protein known as ETHYLENE INSENSITIVE 2 or EIN2. As soon as ethylene binds to its receptors, though, CTR1 looses its paralyzing grip on EIN2 and EIN2 becomes active. But nobody knew how.

Since the activity of the gene, which was isolated in Ecker’s lab in 1995, doesn’t change, Qiao took a closer look at protein levels. It quickly became clear that EIN2 is a short-lived protein that is constantly recycled. When she treated the plants with ethylene, however, EIN2 was no longer degraded and started to accumulate.

Further experiments revealed that two so-called F-box proteins, ETP1 and ETP2 (EIN2 targeting protein 1 and 2), flag EIN2 for degradation when it is not needed for signal transmission. In the presence of ethylene, both F-box proteins are inactivated and EIN2 is no longer sent to the cell’s recycling plant.

“Protein degradation is an emerging theme in plant biology and has been linked to several signaling pathways,” explains Ecker. “This type of regulation is like having your foot on the accelerator and the brake at the same time, then letting up on the brake. It allows cells to respond quickly to incoming information.”

When Qiao inactivated both ETP1 and ETP2 the ethylene signaling pathway was permanently active. When she increased their levels above normal the plants did not respond to the presence of ethylene at all because they couldn’t shake off ETP1 and ETP2. “It really confirmed the central role of EIN2,” say Qiao. “Now we can follow this route and fill in the gaps between EIN2 and downstream components of the pathway.”

Graduate student Katherine N. Chang, and postdoctoral researcher Junshi Yazaki, Ph.D., both in Ecker’s lab also contributed to the study.

The work was funded by the National Science Foundation.

The Salk Institute for Biological Studies in La Jolla, California, is an independent nonprofit organization dedicated to fundamental discoveries in the life sciences, the improvement of human health, and the training of future generations of researchers. Jonas Salk, M.D., whose polio vaccine all but eradicated the crippling disease poliomyelitis in 1955, opened the Institute in 1965 with a gift of land from the City of San Diego and the financial support of the March of Dimes.

Gina Kirchweger | Newswise Science News
Further information:
http://www.salk.edu

More articles from Life Sciences:

nachricht Topologische Quantenchemie
21.07.2017 | Max-Planck-Institut für Chemische Physik fester Stoffe

nachricht Topological Quantum Chemistry
21.07.2017 | Max-Planck-Institut für Chemische Physik fester Stoffe

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

Stanford researchers develop a new type of soft, growing robot

21.07.2017 | Power and Electrical Engineering

Vortex photons from electrons in circular motion

21.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>