Chromosome imbalances lead to predictable plant defects

November 03, 2010

WEST LAFAYETTE, Ind. - Physical defects in plants can be predicted based on chromosome imbalances, a finding that may shed light on how the addition or deletion of genes and the organization of the genome affects organisms, according to a study involving a Purdue University researcher.

The findings identify easily measured characteristics that vary with imbalances of specific chromosomes, said Brian Dilkes, a Purdue assistant professor of horticulture. Understanding why and how those imbalances result in certain characteristics could open the door to correcting those defects in not only plants, but also in animals and humans.

A classic example in humans is in Down syndrome, which is caused by an extra copy of chromosome 21.

"The ability of an organism to replicate and pass on all its genes is incredibly important," Dilkes said. "What we've found is that genes are sensitive to their dose relative to the rest of the genome. When that balance is disrupted, the organisms fail."

In plants, an imbalance in chromosome number can cause defects in stems, leaves, flowers and other physical features. Understanding how those imbalances cause changes could allow scientists to manipulate plant traits to increase biomass for fuels or other purposes.

"By learning the rules, we can predict the outcome of adding or deleting a gene from an organism," Dilkes said. "We see predictable physical consequences for variation in chromosome dosages. This problem is tractable."

Dilkes, a co-author of the findings released in the early online version of the journal Genetics, was part of a team as a project scientist at the University of California-Davis Genome Center that studied chromosome dosage in the research plant Arabidopsis thaliana. The team used naturally occurring and laboratory-created plants with multiple copies of each chromosome, called polyploids, and then crossed them to create aneuploids, or plants with an irregular number of chromosomes.

The aneuploids, which had either an excess or deficiency of a chromosome, were tested to see which chromosomes were deficient or excessive. Those plants were then phenotyped, recording their physical characteristics. The phenotypes and chromosome imbalances were compared, and it became clear that more or less of particular chromosomes corresponded to specific phenotypic characteristics.

Plants with excess chromosome 1 and a deficiency of chromosome 3 had increased stem diameter, for example. To test the finding, plants were created that had both an excess of chromosome 1 and were deficient in chromosome 3, and stem diameter grew as predicted.

In a surprising turn, the team found that chromosomal imbalance resulted in abnormal traits expressed in its offspring. Plants with a normal number of chromosomes that were descended from plants with chromosome imbalances should have been normal but still displayed abnormal characteristics.

"Something about those chromosomes is different," Dilkes said. "We have no idea what that something is, but it suggests there are multigenerational consequences to changes in chromosome dosage. The DNA sequence says these plants should be perfectly normal, but they are not."

Dilkes said future research would focus on chromosome imbalances in crop plants such as corn and trying to understand how the excess or deficiency of a gene leads to a particular phenotypic characteristic.
-end-
The National Science Foundation funded the research.

Writer: Brian Wallheimer, 765-496-2050, bwallhei@purdue.edu

Source: Brian Dilkes, 765-494-2584, bdilkes@purdue.edu

PHOTO CAPTION:

Brian Dilkes was part of a team that determined that plant physical defects can be predicted based on chromosome imbalances. (Purdue Agricultural Communication photo/Tom Campbell)

A publication-quality photo is available at dilkes-chromosomes.jpg

Abstract on the research in this release is available at: http://www.purdue.edu/newsroom/research/2010/101103DilkesChromosomes.html

Purdue University

Related Genome Articles from Brightsurf:

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.

Breakthrough in genome visualization
Kadir Dede and Dr. Enno Ohlebusch at Ulm University in Germany have devised a method for constructing pan-genome subgraphs at different granularities without having to wait hours and days on end for the software to process the entire genome.

Sturgeon genome sequenced
Sturgeons lived on earth already 300 million years ago and yet their external appearance seems to have undergone very little change.

A sea monster's genome
The giant squid is an elusive giant, but its secrets are about to be revealed.

Deciphering the walnut genome
New research could provide a major boost to the state's growing $1.6 billion walnut industry by making it easier to breed walnut trees better equipped to combat the soil-borne pathogens that now plague many of California's 4,800 growers.

Illuminating the genome
Development of a new molecular visualisation method, RNA-guided endonuclease -- in situ labelling (RGEN-ISL) for the CRISPR/Cas9-mediated labelling of genomic sequences in nuclei and chromosomes.

A genome under influence
References form the basis of our comprehension of the world: they enable us to measure the height of our children or the efficiency of a drug.

How a virus destabilizes the genome
New insights into how Kaposi's sarcoma-associated herpesvirus (KSHV) induces genome instability and promotes cell proliferation could lead to the development of novel antiviral therapies for KSHV-associated cancers, according to a study published Sept.

Better genome editing
Reich Group researchers develop a more efficient and precise method of in-cell genome editing.

Unlocking the genome
A team led by Prof. Stein Aerts (VIB-KU Leuven) uncovers how access to relevant DNA regions is orchestrated in epithelial cells.

Read More: Genome News and Genome Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.