Not only humans compensate: Dosage compensation of sex chromosomes in plants

May 16, 2012 By Peter Rüegg
The white campion: the established system of dosage compensation in mammals re-evolved in this inconspicuous plant ten million years ago. Credit: flickr.com

Swiss researchers have found evidence that plants also "invented" the dosage compensation of sex chromosomes. They detected this phenomenon in the white campion.

Despite their different evolutionary paths, the white campion (Silene latifolia) and humans have got something in common: the XX/XY system of their . Male and female flowers can be found on different individuals in this plant, which is quite rare in higher as most of them are hermaphroditic. The “males” have an X and a Y chromosome like men; the females have two X chromosomes like women.

In humans, this system is old. The Y chromosome has degenerated considerably over millions of years and hardly carries functioning genes anymore. Evolutionary scientists assume that so-called dosage compensation balances out the massive loss of genes and their gene products from the Y chromosome. It is a fundamentally important process to prevent an imbalance in an organism.

In humans, one of the woman’s X chromosomes is deactivated so that the man’s X chromosome and the woman’s remaining X chromosome produce the same number of gene products – in other words, RNA or proteins. In the case of the fruit fly Drosophila, however, the genes on the male’s X chromosome are copied twice as often to compensate for the presence of two X chromosomes in the female.

X compensates for the loss

This dosage compensation is also found in the white campion, as ETH-Zurich researchers Niklaus Zemp and Alex Widmer, professors of ecological plant genetics, demonstrated in a plant for the first time based on genetic studies in collaboration with colleagues from the University of Lyon. Genes from the male X chromosome are copied all the more strongly, the weaker the expression of the genes of the Y chromosome. The expression patterns in male and female plants exhibited similar high values of the genes that lie on the sex chromosomes, independently of how strongly the Y chromosome is copied in general.

Therefore, X compensates for the loss of Y to enable male and female plants to reach the same dosage. “Until now, dosage compensation could only be observed in the very old sex chromosome system in animals,” says Widmer. This supposedly developed 150 million years ago. The white campion is now the first plant in which this phenomenon has been detected.

A young system

For the biologists, this also means that dosage compensation in plants only evolved recently and that, no sooner than the sex chromosome system appears in an organism, it can develop extremely quickly. Widmer estimates that the system found in the white campion is “only” ten million years old and therefore still young from an evolutionary point of view. “However, our findings indicate that ten million years are sufficient for the dosage compensation system to re-evolve.”

For their study, the ETH-Zurich scientists analyzed around thirty-five billion components of the genetic code from six plant individuals using state-of-the-art sequencing technology, so-called next generation sequencing. This enables the genetic code to be determined at high speed and with great precision.

Dosage compensation and trisomy 21

Dosage compensation is extremely important for organisms. During the division of sex cells in humans, for instance, it can happen that certain chromosomes are not divided cleanly. As a result, one egg cell only receives one relevant chromosome and the other three. The “overproduction” that starts from one of the surplus can cause severe damage. In humans, for instance, trisomy 21 is a fairly rare but widespread phenomenon. Those affected have three copies of Chromosome 21 instead of two. The overdose of from this chromosome triggers the characteristic symptoms.

Explore further: Free the seed: OSSI nurtures growing plants without patent barriers

More information: Muyle A, et al. (2012) Rapid De Novo Evolution of X Chromosome Dosage Compensation in Silene latifolia, a Plant with Young Sex Chromosomes. PLoS Biol, doi:10.1371/journal.pbio.1001308

add to favorites email to friend print save as pdf

Related Stories

New thinking on regulation of sex chromosomes in fruit flies

Sep 19, 2011

Fruit flies have been indispensible to our understanding of genetics and biological processes in all animals, including humans. Yet, despite being one of the most studied of animals, scientists are still finding the fruit ...

X chromosome exposed

May 29, 2008

Researchers from the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, and the EMBL-European Bioinformatics Institute (EMBL-EBI) in Hinxton, UK, have revealed new insights into how sex chromosomes are regulated. ...

Sex and the single chromosome

Nov 26, 2010

Is there value to sex? For higher organisms, absolutely. Animals, plants and fungi that reproduce only by cloning are scarce as hen's teeth, suggesting the gene shuffling of sex pays handsome dividends.

Fortunately for men, size doesn't matter (much)

Jan 10, 2012

(PhysOrg.com) -- Researchers from The Australian National University have discovered that the male-specific Y-chromosome is shrinking – and it’s happening at different rates across species.

Recommended for you

User comments : 0

More news stories

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.