Two worms are better than one

November 17, 2003

Caenorhabditis elegans, a 1-mm soil-dwelling roundworm with 959 cells, may be the best-understood multicellular organism on the planet. As the most "pared-down" animal that shares essential features of human biologyfrom embryogenesis to agingC. elegans is a favorite subject for studying how genes control these processes. The way these genes work in worms helps scientists understand how diseases like cancer and Alzheimer's develop in humans when genes malfunction. With the publication of a genome sequence of C. elegans' first cousin, C. briggsae, Lincoln Stein and colleagues have greatly enhanced biologists' ability to mine C. elegans for biological gold.

After confirming the accuracy of the sequence (it covers 98% of the genome and has an accuracy of 99.98%), the researchers turned to the substance of the genome. Examining the two worm genomes side by side, scientists can quickly spot genes and flag interesting regions for further investigation. Analyzing the organization of the two genomes, Stein et al. not only found strong evidence for roughly 1,300 new C. elegans genes, but also indications that certain regions could be "footprints of unknown functional elements." While both worms have roughly the same number of genes (about 19,000), the C. briggsae genome has more repeated sequences, making its genome slightly larger. The size is estimated to be just over 100 million base pairs, about 1/30 the size of the human genome.

Because the worms set out on separate evolutionary paths about the same time mice and humans parted ways--about 100 million years ago, compared to 75 million years ago--the authors could compare how the two worm genomes have diverged with the divergence between mice and humans. The worms' genomes, it seems, are evolving faster than their mammalian counterparts, based on the change in the size of the protein families (C. elegans has more chemosensory proteins than C. briggsae, for example), the rate of chromosomal rearrangements, and the rate at which silent mutations (DNA changes with no functional effect) accumulate in the genome. This would be expected, the researchers point out, because generations per year are a better measure of evolutionary rate than years themselves. (Generations in worms are about three days; in mice, about three months.)

What is surprising, they say, is that despite these genomic differences, the worms look nearly identical and occupy similar ecological niches; this is obviously not the case with humans and mice, which nevertheless have remarkably similar genomes. It's the quality, rather than the quantity of the changes in the genome, that's important. The nature of these changes, along with many other issues, can now be explored by searching the two species' genomes and comparing those elements that have been conserved with those that have changed.

With the C. briggsae genome sequence in hand, worm biologists have a powerful new research tool. By comparing the genetic makeup of the two species, C. elegans researchers can refine their knowledge of this tiny human stand-in, fill in gaps about gene identity and function, as well as illuminate those functional elements that are harder to find, and study the nature and path of genome evolution.
-end-
research article: http://www.plos.org/downloads/plbi-01-02-stein.pdf

cover art: http://www.plos.org/downloads/Cbriggsae_frontcover.pdf

http://www.plos.org/downloads/Cbriggsae.jpg

CONTACT:

Lincoln Stein
Cold Spring Harbor Laboratory
Cold Spring Harbor, NY 11724
United States of America
516-367-8380
lstein@cshl.org

Richard Durbin
Wellcome Trust Sanger Institute
Hinxton
Cambridge
CB10 1SD
44-1223-834244
rd@sanger.ac.uk

PLOS

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.