Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers Identify Key Molecular Signal in Plant Pollination

11.07.2003


Nearly 80 percent of the world’s food begins as seeds, including such staple crops as corn, wheat and rice. Despite the importance and ubiquity of seeds, researchers have learned precious little about the processes that regulate plant fertilization, the essential first step in seed formation.


Pollen tubes (red tubules) from the pop2 mutant grow in a tangled mass within female tissues. Rather than efficiently growing up to an ovule (upper right), they instead gather at the ovule’s base.

Photo: Anna Edlund



Now, Howard Hughes Medical Institute (HHMI) researchers have identified a key molecular signal that regulates the growth and guidance of the “pollen tube,” a tunnel formed by the pollen grain that aids in fertilizing the plant’s eggs. They say their initial findings could open a new route to understanding the multitude of interacting control signals that likely guide the pollen tube on its crucial journey.

In an article published in the July 11, 2003, issue of the journal Cell, HHMI investigator Daphne Preuss and her colleagues at the University of Chicago report that the molecule gamma-amino butyric acid (GABA), best known for its role as a neurotransmitter in the mammalian nervous system, is a key signaling molecule that triggers plant reproduction.


“When a pollen grain is deposited on the surface of a flower, it’s like a speck of dust landing on the skin,” said Preuss. “The fertilization process is unlike that in animals, in which the sperm swim through a well-defined cavity. Instead, this pollen grain somehow has to grow a tube from the stigma of the flower, digesting tissue to burrow all the way inside to where the eggs are.

“While a few molecules involved in this process have been identified over the years, we really still don’t understand how this tube gets from start to finish,” said Preuss. “And since the world’s agriculture depends so profoundly on plant fertility, understanding this process is fundamentally important.”

The study began when co-author Laura Brass analyzed a peculiar mutant form, called pop2, of the plant Arabidopsis. A member of the mustard family that also includes cabbage and radish, Arabidopsis is the most popular plant model for biologists, since it is small, prolific, easily grown and has a rapid life cycle.

“When we saw the pollen tubes in pop2 just winding around and totally missing their targets, it just seemed like this was a mutant worth studying,” said Preuss. After laboriously identifying genetic markers in the pop2 genome, Brass pinpointed one specific gene that caused the defect observed in the pop2 mutant. The researchers named the gene POP2.

Lead author of the Cell paper, Ravishankar Palanivelu, compared the sequence of the defective protein produced by the gene POP2 to other known proteins and concluded that it was an enzyme called an aminotransferase. However, it was not until the researchers analyzed an extract of the mutant plant — discovering a hundred-fold elevation in GABA — that they learned which plant molecule the enzyme normally degraded.

Further studies using fluorescent-labeled antibodies to GABA confirmed that the chemical normally concentrates in the pollen tubes near the egg-containing ovule. In contrast, in the pop2-mutant plants, GABA is diffused throughout the tissues.

The researchers did antibody staining and microdissection of normal Arabidopsis ovules, which revealed a concentration gradient of GABA that could act as an attractant for the pollen tube. However, they found, such a gradient was lacking in the pop2-mutants, because the malfunction of the enzyme that breaks down GABA produces a massive increase in the chemical signal. Also, in vitro experiments revealed that pollen required GABA to stimulate growth of pollen tubes. Finally, the researchers conducted studies of various crossbred plants that demonstrated the requirement for a GABA gradient in pollen tube guidance.

“So, in the mutants, the pollen tubes are just overwhelmed with signal, like someone staring at the sun and trying to find their way,” said Preuss. “But in the wild-type plants, the pollen tubes have the molecular equivalent of just the right amount of light to guide them where they need to go.”

According to Preuss, identifying GABA as a key pollen-tube guidance signal represents only the beginning of their exploration of the pollen-tube guidance control machinery. For example, she said, to gain further insight into the machinery, the researchers are analyzing other mutants affecting pollen tube growth, as well as the reproductive metabolic changes in the tissues as they develop.

Jim Keeley | HHMI
Further information:
http://www.hhmi.org/news/preuss2.html

More articles from Life Sciences:

nachricht New application for acoustics helps estimate marine life populations
16.01.2018 | University of California - San Diego

nachricht Unexpected environmental source of methane discovered
16.01.2018 | University of Washington Health Sciences/UW Medicine

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Gran Chaco: Biodiversity at High Risk

17.01.2018 | Ecology, The Environment and Conservation

Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials

17.01.2018 | Physics and Astronomy

Fraunhofer HHI receives AIS Technology Innovation Award 2018 for 3D Human Body Reconstruction

17.01.2018 | Awards Funding

VideoLinks
B2B-VideoLinks
More VideoLinks >>>