Nav: Home

Hydrogen peroxide assists sexual reproduction in spruce

May 16, 2018

Plant physiologists from MSU proved for the first time that dangerous reactive oxygen species that are often considered as by-products of energy generation in cells, are required by the conifers to fertilize the egg cell. Experiments with pollen of blue spruce (Picea pungens) helped to find a protein that makes the whole system work. The scientists believe that the obtained data will lead to the optimization of conifer forests restoration. The results of the study were published in the Plant Reproduction journal.

"The study of sexual reproduction in conifers is on its early stage, and many of it`s aspects are practically unknown," - says the co-author of the article Maria Breygina, a senior scientific researcher at the department of plant physiology, Faculty of Biology, MSU, and a scientific fellow of the electrophysiology lab at Pirogov Russian National Research Medical University. - "These studies are of high fundamental importance, as the pollen of conifers is a more ancient object with directional growth compared to that of flowering plants."

Flowering plants have flowers with stamens distributing the pollen and pistils where it has to get for fertilizing. Cross pollination is usually more advantageous for a plant, as it helps to increase genetic diversity. The seeds in flowering plants are formed inside an ovary which, in turn, forms a fruit (that is why flowering plants are also called angiosperms). However, gymnosperms (of which conifers are the best-known group) also have mechanisms for cross pollination. In conifers these are cones that are actually modified sprouts. The cones of conifers are diclinous; male ones are relatively small and produce pollen that is distributed by wind, and female ones are bigger and form seeds. After reaching the female cone, pollen sticks to special liquid (in pines and spruce) or small hairs (as in Douglas fir).

Having landed in the right place (on a pistil in flowering plants or under a seed scale in gymnosperms), pollen starts to grow forming a pollen tube. Through this tube sperm cells reach to egg cell to fertilize it. In flowering plants the second sperm fuses with a central cell to form endosperm (a nutritional part of the seeds, for example, as in wheat seeds). That is why this fertilization type is called double fertilization.

All these processes were described long ago, but modern science is focused on their molecular and biochemical aspects. It has been recently established that reactive oxygen species (ROS) play a key role in pollen germination in angiosperms. ROS are neutral or negatively charged particles in which oxygen has an unpaired electron. ROS include peroxides (in particular, hydrogen peroxide) and radicals, such as superoxide radical O2-.

An unpaired electron makes ROS highly reactive. If a lot of ROS is formed within a cell, the consequences may be severe. These compounds may affect the balance of complex biochemical reactions, damage membranes, DNA, and other parts of cells. That is why, regardless of their origin, ROS are often considered dangerous by-products that need to be neutralized as quickly as possible. Still, certain cells synthesize them in small quantities and use as a messenger. Due to the ambiguous nature of these compounds, it is extremely important to study the useful functions of ROS, such as their role in plant fertilization.

Plant physiologists from MSU were the first to study the role of ROS in pollen germination in conifers (namely, blue spruce) and found out that pollen grains secrete hydrogen peroxide and O2- into the environment before germinating. Later on hydrogen peroxide gradient is formed in the pollen tube, i.e. its concentration is increased in the tip. This gradient seems to be necessary for the tube to grow to the egg cell, as well as to support the membrane potential (negative charge) gradient (which is described in conifers for the first time), though these gradients do not seem to be related directly.

The scientists also found out what protein regulates this process. It turned to be NADPH-oxidase located in cell membranes. This protein is in charge of moving electrons out of the cell and the formation of extracellular superoxide. ROS interconvert quite quickly, O2- turns into peroxide that re-enters the cell. Due to this process hydrogen peroxide is distributed gradiently in the pollen tube. Experiments have shown that after NADPH oxidase suppression pollen grains do not germinate, and pollen tubes become unable to grow. Therefore, fertilization doesn't take place.

"The results of this and further studies may be used to optimize forest restoration, especially fir trees, cedars, pines, and silver-firs, as well as their selection and forming a collection of forest breeds in Russia," -- commented Maria Breygina.

All the authors of the article study or work at MSU. Maria was in charge of drafting the article and processing experimental data obtained by PhD student Nikita Maksimov and undergraduate student Anastasiya Evmenyeva. The idea was developed by Igor Ermakov, Doctor of Biology, professor of the plant physiology department, and the coordinator of the study.
-end-


Lomonosov Moscow State University

Related Protein Articles:

Protein aggregation: Protein assemblies relevant not only for neurodegenerative disease
Amyloid fibrils play a crucial role in neurodegenerative illnesses. Scientists from Heinrich Heine University Düsseldorf (HHU) and Forschungszentrum Jülich have now been able to use cryo-electron microscopy (cryo-EM) to decode the spatial structure of the fibrils that are formed from PI3K SH3 domains - an important model system for research.
Old protein, new tricks: UMD connects a protein to antibody immunity for the first time
How can a protein be a major contributor in the development of birth defects, and also hold the potential to provide symptom relief from autoimmune diseases like lupus?
Infection-fighting protein also senses protein misfolding in non-infected cells
Researchers at the University of Toronto have uncovered an immune mechanism by which host cells combat bacterial infection, and at the same time found that a protein crucial to that process can sense and respond to misfolded proteins in all mammalian cells.
Quorn protein builds muscle better than milk protein
A study from the University of Exeter has found that mycoprotein, the protein-rich food source that is unique to Quorn products, stimulates post-exercise muscle building to a greater extent than milk protein.
More than a protein factory
Researchers from the Stowers Institute for Medical Research have discovered a new function of ribosomes in human cells that may show the protein-making particle's role in destroying healthy mRNAs, the messages that decode DNA into protein.
More Protein News and Protein Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...