A molecular mechanism by which gene silencing is regulated at the genome-wide level in plants has been uncovered by a research team led by Motoaki Seki of the RIKEN Plant Science Center, Yokohama. The researchers propose that a similar mechanism may also help to protect plant genomes from the potentially harmful effects of DNA elements, such as transposons, or ‘jumping genes’. “If left unhindered, transposable elements can cause havoc in the genome, for example by inserting themselves into essential genes,” says Seki.
The DNA of eukaryotes—organisms with nucleated cells—is packaged in a complex structure called chromatin within chromosomes. Chromatin also contains DNA-binding proteins called histones. When in its open conformation, known as euchromatin, the DNA is accessible to transcription factors, allowing gene expression to proceed. However, when in its highly condensed form—heterochromatin—gene expression is silenced.
The transition from euchromatin to heterochromatin requires chemical modification of both DNA and histones. These so-called epigenetic changes involve the methylation of DNA by enzymes called DNA methyltransferases, and the elimination of epigenetic marks on histones by other enzymes called histone deacetylases. In addition to silencing gene expression, heterochromatin formation may protect against the potentially damaging effects of transposons by blocking their replication.
Seki and his colleagues studied the regulation of heterochromatin formation in Arabidopsis thaliana, a small flowering related to the mustard plant. “Arabidopsis is a widely used model species for studying epigenetic changes in plants,” explains Seki.
Uniquely in plants, DNA methylation resulting in heterochromatin formation is triggered by small RNA molecules. This process is known as RNA-directed DNA methylation, and involves the DNA methyltransferase MET1 and the histone deacetylase HDA6. However, the overall role of HDA6 in heterochromatin formation remained unclear.
By comparing the RNA transcript profiles of normal and mutant plants lacking functional HDA6, the researchers identified 157 target genes spread across the Arabidopsis genome. In some target genes in the mutant plants they found that DNA methylation was completely lost, allowing these genes to be expressed. They also found that the target specificity of HDA6 was unexpectedly much greater than that of MET1.
“Our findings suggest that HDA6 recruits MET1 to specific target genes, allowing it to regulate gene silencing on a genome-wide scale,” says Seki.
In addition to this general role, the researchers propose that HDA6 may regulate transposon silencing through heterochromatin formation in plant gametes. They also express the hope that their research will help illuminate related processes in humans.
The corresponding author for this highlight is based at the Plant Genomic Network Research Team, RIKEN Plant Science Center
'Y' a protein unicorn might matter in glaucoma
23.10.2017 | Georgia Institute of Technology
Microfluidics probe 'cholesterol' of the oil industry
23.10.2017 | Rice University
Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
23.10.2017 | Event News
17.10.2017 | Event News
10.10.2017 | Event News
23.10.2017 | Life Sciences
23.10.2017 | Physics and Astronomy
23.10.2017 | Health and Medicine