Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ejaculation in the maize flower

22.06.2010
Sperm swim to egg cells and fertilize them – at least that is what happens in people. In many flowering plants, however, the sperm cells are immobile. So, how do they reach their destination? Researchers from Würzburg and Regensburg know the answer.

The sperm cells of flowering plants are found in pollen grains that are carried on the wind or by insects to other flowers. There they germinate: they form tubes containing two sperm cells each and penetrate the tissue of the ovary as far as the ovules. These contain the egg cells, each flanked by two helper cells.

How does a pollen tube find its way to one of the numerous ovules? This question has occupied the minds of plant scientists ever since Eduard Strasburger’s time (1844-1912). This botanist from Bonn had already successfully described fertilization in plants – based on nothing more than observations under a microscope.

“Today we know that the helper cells release a signaling substance that entices the pollen tube,” says Professor Thomas Dresselhaus from Regensburg. This finding was published by his working group in 2009. Together with plant researchers Dirk Becker and Dietmar Geiger from the Department of Molecular Plant Physiology and Biophysics at the University of Würzburg, the Regensburg scientists have now discovered a new signaling substance that lets the pollen tube rupture close to the egg cells. This result has been published in the magazine PLoS Biology.

Signaling substance in the defensin mould

The newly discovered signaling substance is a protein molecule that closely resembles the so-called defensins. Plants produce huge variations of these proteins in their male and female sex organs. Until now, science assumed that defensins protect the gametes and the developing seed against pathogens. This is because defensins are originally part of the immune system of animals and plants; they combat germs such as bacteria and fungi.

However, defensins clearly play an important role in sex between plants as well. This is borne out by the findings made by the Regensburg and Würzburg researchers using maize: in its ovules the helper cells release a special form of defense proteins, known as ZmES1-4 defensins.

Pollen tube ruptures alongside the egg cells

One of the defensins entices the pollen tube, another causes it to rupture as soon as it is right next to the egg cells – a kind of ejaculation that sets the immobile sperm cells free so that fertilization can occur. “The ZmES1-4 defensins open potassium ion channels in the pollen tube,” reports Dirk Becker and Dietmar Geiger, “resulting in an explosive release of sperm cells.”

New plant hybrids?

These findings offer the promise of new application possibilities: they mean that, where possible, the natural barriers that prevent cross-fertilization between different plant species can be overcome.

“It would be desirable, for example, to incorporate the properties of certain wild grasses into grains through cross-fertilization,” explains Dirk Becker. It may be possible to achieve such results in the future by manipulating the potassium channels or defensins.

Findings on the evolution of procreation

The researchers’ work also delivers fresh insights into plant evolution. “Our results indicate that even the very first plants on the earth some 470 million years ago and later also the flowering plants that first sprung up around 170 million years ago used disease defense mechanisms and adapted them to develop new procreation strategies.”

The evolutionary predecessors of the flowering plants – mosses and ferns – have mobile sperm cells, as do some flowering plants themselves. The majority of flowering plants, however, have changed the strategy they use to bring sperm cells and egg cells together: their sperm cells are immobile, and a pollen tube assumes responsibility for carrying them purposefully to the egg cells.

Contact

Dr. Dirk Becker, Department of Botany I – Molecular Plant Physiology and Biophysics at the University of Würzburg, phone +49 (0)931 31-86108, dbecker@botanik.uni-wuerzburg.de

“Defensin-Like ZmES4 Mediates Pollen Tube Burst in Maize via Opening of the Potassium Channel KZM1”, Suseno Amien, Irina Kliwer, Mihaela L. Márton, Thomas Debener, Dietmar Geiger, Dirk Becker, Thomas Dresselhaus, PLoS Biology 8(6): e1000388. doi:10.1371/journal.pbio.1000388

Robert Emmerich | idw
Further information:
http://www.uni-wuerzburg.de/

More articles from Life Sciences:

nachricht Sleep as energy saving mode
21.11.2017 | Universitätsspital Bern

nachricht Water world
20.11.2017 | Washington University in St. Louis

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Antarctic landscape insights keep ice loss forecasts on the radar

20.11.2017 | Earth Sciences

Filling the gap: High-latitude volcanic eruptions also have global impact

20.11.2017 | Earth Sciences

Water world

20.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>