Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Direct transfer of plant genes from chloroplasts into the cell nucleus

16.04.2012
Gene function preserved despite structural differences in the DNA

Chloroplasts, the plant cell’s green solar power generators, were once living beings in their own right. This changed about one billion years ago, when they were swallowed up but not digested by larger cells.


Fast-forwarding evolution. A gene’s jump from the chloroplast genome into that of the nucleus is made visible here through the development of antibiotic resistance. In the two green shoots, the resistance gene has migrated into the cell nucleus, where it can be correctly read, thus allowing the plant to grow on an antibiotic-containing medium. © Max Planck Institute of Molecular Plant Physiology

Since then, they have lost much of their autonomy. As time went on, most of their genetic information found its way into the cell nucleus; today, chloroplasts would no longer be able to live outside their host cell. Scientists in Ralph Bock’s team at the Max Planck Institute of Molecular Plant Physiology have discovered that chloroplast genes take a direct route to the cell nucleus, where they can be correctly read in spite of their architectural differences.

Cyanobacteria are among the oldest life forms, and appear to be the forerunners of green chloroplasts in plant cells. They do not possess a true cell nucleus, but their genetic substance is made up of the same four building blocks as that of humans, plants and animals. Therefore, the genes encoded in the chloroplast DNA can also be read in the cell nucleus; indeed, many genes that were still found in the cell organelles during early evolution are now located exclusively in the genome of the nucleus. How they made their way there has previously been unclear. Two mechanisms appeared likely: either direct transport in the form of DNA fragments from the chloroplasts to the nucleus or transport in the form of mRNA, which is then transcribed back into DNA.

The direct transfer of DNA appears to predominate in the chloroplasts, but this pathway raises two problems. The first problem lies in the promoters, the DNA sequences which ensure that genes are recognised as such. They are located upstream of the genes and recruit proteins that are required for transcription of the genes. However, promoters from chloroplasts are not recognised as such by the proteins in the nucleus, so that the DNA reading machinery should overlook these incoming genes.

The second difficulty is in the correct processing of the gene sequence. Genes consist of several modules, separated by non-coding DNA regions (introns). Since the introns obstruct protein synthesis, they need to be removed from the mRNA, a procedure described as splicing. The whole process, ending in synthesis of the correct protein, can resume only once this has taken place. Once again, however, the mRNA is processed differently in the cell nucleus than in the chloroplasts, and for a long time, chloroplast introns seemed to have been an insurmountable hurdle for the correct reading of chloroplast genes in the nucleus.

“But they are actually nothing of the sort”, stresses Ralph Bock, head of the research group. “Our trials have shown that the introns are recognised in the cell nucleus and spliced out, even if not always at exactly the same sites as might have been the case in the chloroplasts.” Functional proteins are formed despite this. It is thought that the introns even help the splicing enzymes by folding themselves into stable RNA structures, thus directing the enzymes to the right locations. At the same time, the RNA structure seems to help the ribosomes find the correct starting point for protein synthesis.

Since the transfer of genes into the cell nucleus is an extremely slow evolutionary process, which has taken nature millions of years, it has not been possible to investigate the underlying mechanism to date. However, researchers have now managed to fast-forward this gene transfer in the laboratory. Because the cells were subjected to high selection pressure, the transference of genes from the chloroplasts into the nucleus became essential for survival, so that it could be made readily visible. It was found that the transfer takes place without the involvement of RNA and that the DNA apparently jumps directly from the cell’s chloroplasts into its nucleus.

Contact
Prof. Dr. Ralph Bock
Max Planck Institute of Molecular Plant Physiology, Potsdam
Phone: +49 331 567-8702
Email: rbock@mpimp-golm.mpg.de
Claudia Steinert
Max Planck Institute of Molecular Plant Physiology, Potsdam
Phone: +49 331 567-8275
Fax: +49 331 567-8408
Email: Steinert@mpimp-golm.mpg.de
Original publication
Ignacia Fuentes, Daniel Karcher, Ralph Bock
Experimental Reconstruction of Functional Gene Transfer of Intron-containing Chloroplast Genes to the Nucleus

Current Biology, 12 April 2012 DOI: 10.1016/j.cub.2012.03.005

Prof. Dr. Ralph Bock | Max-Planck-Institut
Further information:
http://www.mpg.de/5610272/chloroplasts_cell_nucleus

More articles from Life Sciences:

nachricht Historical rainfall levels are significant in carbon emissions from soil
30.05.2017 | University of Texas at Austin

nachricht 3D printer inks from the woods
30.05.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New Method of Characterizing Graphene

Scientists have developed a new method of characterizing graphene’s properties without applying disruptive electrical contacts, allowing them to investigate both the resistance and quantum capacitance of graphene and other two-dimensional materials. Researchers from the Swiss Nanoscience Institute and the University of Basel’s Department of Physics reported their findings in the journal Physical Review Applied.

Graphene consists of a single layer of carbon atoms. It is transparent, harder than diamond and stronger than steel, yet flexible, and a significantly better...

Im Focus: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

3D printer inks from the woods

30.05.2017 | Life Sciences

How circadian clocks communicate with each other

30.05.2017 | Life Sciences

Graphene and quantum dots put in motion a CMOS-integrated camera that can see the invisible

30.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>