The DNA of the Y chromosome in the white campion, a flowering plant that has separate sexes like humans, has been deciphered by an international team with a significant Czech input.

In the current issue of the journal Science, the researchers describe the origin and further evolution of the Y chromosome, which is unusually large in this plant. They have also identified possible genes responsible for sex determination. The new findings provide a closer understanding of the evolution and genetics of sexual reproduction in plants and other organisms, including humans. The Institute of Experimental Botany and the Institute of Biophysics, both parts of the Czech Academy of Sciences, were involved in the research.

Most flowering plants have bisexual flowers with both male and female reproductive organs. However, some species have separate sexes - in their population there are individuals with exclusively female or, on the contrary, male flowers. These so-called dioecious plants include holly, hemp, most species of willow, stinging nettle and hops. Evolutionary development and the genetic basis of plant sexuality are important topics for biological and agricultural research.

An international team of scientists from eight European countries, the USA and Chile has thoroughly investigated the genetic information of the Y sex chromosome in the dioecious herb white campion (Silene latifolia). This plant has a sex determination system similar to that of humans. Male individuals carry X and Y chromosomes, while female individuals, which only produce ovaries in flowers but not anthers and pollen, have a pair of X chromosomes.

A male plant of the white campion. General appearance on the left, detail of the flowers on the right. Photo: Zdeněk Kubát.

The giant chromosome as a scientific challenge

Deciphering the DNA of the Y chromosome in the white campion was an extremely difficult task. This chromosome contains many repetitive stretches of DNA, which complicates its analysis. Moreover, it is huge - it has over 500 million "letters" of genetic information. This is about four times more than the complete hereditary information (genome) of Arabidopsis and almost one sixth of the entire human genome with 23 chromosomes.

The authors of the recently published study therefore used a combination of several state-of-the-art DNA reading methods to obtain a detailed sequence of the Y chromosome - in simple terms, the order of the "genetic letters" in which the hereditary information is written.

Details of evolutionary history revealed

In addition to the genome of the white campion, the researchers analysed the genomes of two related species that do not have separate sexes - the bladder campion (Silene vulgaris) and the sand catchfly (Silene conica). Their comparison revealed a complicated origin of Silene's sex chromosomes, which evolved from several pieces of other chromosomes.

"Unlike the human Y chromosome, the one in Silene is evolutionarily young. This unique feature allows us to look more closely at the key processes that shape sex chromosomes and influence the nature of reproduction. The Y chromosome in the white campion began to form about 11 million years ago."

"During further evolution, its recombination with the X chromosome, i.e. the pairing and exchange of their corresponding regions, was gradually reduced. It also accumulated repetitive stretches of DNA, which led to its extreme enlargement," says Roman Hobza from the Institute of Biophysics of the Czech Academy of Sciences.

"The published findings will become a starting point for further research on plant reproduction, for example by identifying gene groups that have multiplied or, conversely, been lost in connection with changes in reproduction strategies," adds Helena Štorchová from the Institute of Experimental Botany of the Czech Academy of Sciences.

Scientists have also found genes on the Y chromosome that could be responsible for its primary function, i.e. suppressing ovary development and promoting anther formation and pollen production in male flowers.

Chromosomes of male white campion plants, including the giant Y sex chromosome. Photo: Václav Bačovský.

Significant participation of Czech scientists

Authors from the Czech Republic have significantly contributed to the project. A team from the Institute of Biophysics, led by Roman Hobza, participated in the analysis of the white campion sex chromosomes. Two teams from the Institute of Experimental Botany, led by Helena Štorchová and Hana Šimková, were involved in the assembly of the bladder campion genome.

"The new publication is the result of many years of international effort and shows that even seemingly inconspicuous plants can provide key insights into fundamental biological processes. The white campion is thus becoming one of the important experimental species for understanding the evolution of reproduction."

"At the same time, the knowledge gained from it can be used while studying other plants, including crops, as well as other organisms. Silene research is also helping us to answer questions related to the fate of our own genomes and thus to the fate of ourselves," summarise Helena Štorchová and Roman Hobza.

White campion (Silene latifolia) flowers - female on the left, male on the right. Photo: Zdeněk Kubát.

Stamens in the male white campion flower, from which the calyx and corolla have been removed. Photo: Václav Bačovský.

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Article reference:

Moraga C et al. (2025): The Silene latifolia genome and its giant Y chromosome. Science 387: 630-636. DOI:10.1126/science.adj7430

(paid access; article abstract can be viewed for free)