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
Scientists enlist engineered protein to battle the MERS virus
22.05.2017 | University of Toronto
Insight into enzyme's 3-D structure could cut biofuel costs
19.05.2017 | DOE/Los Alamos National Laboratory
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
For the first time, scientists have succeeded in studying the strength of hydrogen bonds in a single molecule using an atomic force microscope. Researchers from the University of Basel’s Swiss Nanoscience Institute network have reported the results in the journal Science Advances.
Hydrogen is the most common element in the universe and is an integral part of almost all organic compounds. Molecules and sections of macromolecules are...
22.05.2017 | Event News
17.05.2017 | Event News
16.05.2017 | Event News
22.05.2017 | Materials Sciences
22.05.2017 | Life Sciences
22.05.2017 | Physics and Astronomy