Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Researchers identify molecular signaling system that is crucial for plant fertility


University of Chicago researchers have found that a substance that functions as a neurotransmitter in humans also plays a crucial role in plant reproduction, guiding growth of the tube that transports sperm from a pollen grain on a flower’s surface to the egg cells within a plant’s ovules.

Their finding, published in the July 11, 2003, issue of the journal Cell, is a major step forward in understanding plant fertility. The discovery could also help researchers understand similar biological processes, such as now nerve cells find each other and make appropriate connections. It may even provide clues about repairing spinal cord injuries.

"Since agriculture, which supplies nearly 80 percent of the world’s food supply, depends so profoundly on plant fertility, understanding this process is fundamentally important," said Daphne Preuss, Ph.D., professor of molecular and cell biology and an investigator in the Howard Hughes Medical Institute at the University of Chicago.

When a pollen grain is deposited on the surface of a flower, it somehow has to grow a tube from the stigma of the flower, past several different cell types to where the eggs are, digesting tissue as it grows to burrow all the way inside. "While a few molecules involved in this process have been identified over the years," said Preuss, "we really still don’t understand how this tube gets from start to finish."

Working with Arabidopsis, a popular model plant, Preuss and colleagues from her lab found that plants produce a carefully controlled gradient of gamma-amino butyric acid (GABA), a molecule best known for its role in the mammalian nervous system, to lure a pollen tube toward the egg cells. GABA acts like a light at the end of a tunnel, stimulating the initial growth of the pollen tube and shining ever brighter as the tube gets closer to its goal.

The researchers found that the key to regulating GABA levels is an enzyme they named POP2 that degrades GABA. Arabidopsis flowers produce high levels of GABA then eliminate varying amounts of it from different structures, so that a small amount is present at the surface of the pistil, where it stimulates pollen tube growth. Higher concentrations are found closer to the eggs, leading the tubes toward the target.

The study grew out of the team’s chance finding of abnormal pollen tubes on plants that were later found to lack POP2.

"We saw the pollen tubes just winding around and totally missing their targets on one particular mutant," said Preuss. Co-author Laura Brass, a former Ph.D. student in the Preuss lab, analyzed the mutant strain and pinpointed the gene that caused the defect, which the researchers named POP2.

By comparing the sequence of the defective protein produced by POP2 to other known proteins, lead author Ravishankar Palanivelu, Ph.D., a post-doctoral fellow in Preuss’s laboratory, concluded that it was an enzyme called an aminotransferase. It was not until the researchers found that the mutant plant contained a hundred-fold elevation in GABA, however, that they learned which molecule the enzyme degraded.

Further studies confirmed that the chemical normally concentrates near the egg-containing ovule. In contrast, in the mutant plants, GABA is diffused throughout the tissues. In these mutants, the pollen tubes are "just overwhelmed with signal," said Preuss. Instead of a light at the end of the tunnel it was "like staring at the sun."

Finding a reproductive role for GABA in plants is a good example of nature’s ability to make the most of what’s available, said Preuss. GABA is small, comparatively simple molecule. Many plants and animals use it as a source of carbon or nitrogen or to send signals from cell to cell. Animals use it to regulate hormone secretion, inhibit certain signals between nerve cells, and perhaps even to guide embryonic neurons to their destination.

GABA is only one of several substances involved in pollen tube guidance, however, said Preuss. The researchers are analyzing other mutants with altered pollen tube growth.

The research was supported by the Department of Energy, the Searle Scholars Program and the University of Chicago.

John Easton | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Biologists unravel another mystery of what makes DNA go 'loopy'
16.03.2018 | Emory Health Sciences

nachricht Scientists map the portal to the cell's nucleus
16.03.2018 | Rockefeller University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>