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 substance library to accelerate the search for active compounds
14.07.2020 | Helmholtz-Zentrum Berlin für Materialien und Energie

nachricht Green is more than skin-deep for hundreds of frog species
14.07.2020 | Duke 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: Electron cryo-microscopy: Using inexpensive technology to produce high-resolution images

Biochemists at Martin Luther University Halle-Wittenberg (MLU) have used a standard electron cryo-microscope to achieve surprisingly good images that are on par with those taken by far more sophisticated equipment. They have succeeded in determining the structure of ferritin almost at the atomic level. Their results were published in the journal "PLOS ONE".

Electron cryo-microscopy has become increasingly important in recent years, especially in shedding light on protein structures. The developers of the new...

Im Focus: The spin state story: Observation of the quantum spin liquid state in novel material

New insight into the spin behavior in an exotic state of matter puts us closer to next-generation spintronic devices

Aside from the deep understanding of the natural world that quantum physics theory offers, scientists worldwide are working tirelessly to bring forth a...

Im Focus: Excitation of robust materials

Kiel physics team observed extremely fast electronic changes in real time in a special material class

In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...

Im Focus: Electrons in the fast lane

Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.

Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....

Im Focus: The lightest electromagnetic shielding material in the world

Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.

Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

International conference QuApps shows status quo of quantum technology

02.07.2020 | Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

 
Latest News

Color barcode becomes ISO standard

14.07.2020 | Information Technology

New substance library to accelerate the search for active compounds

14.07.2020 | Life Sciences

Green is more than skin-deep for hundreds of frog species

14.07.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>