In many species that have evolved sex chromosomes, the diminutive Y chromosome pales in comparison to a much larger X. But some species, including the unassuming Silene latifolia, buck this trend. This dainty-looking flowering plant, commonly known as white campion, has a Y bigger than the puffer fish’s entire genome. Now, using a new DNA sequencing technique, scientists have finally mapped this oversized chromosome from start to finish.
The researchers discovered that different parts of the white campion’s Y chromosome determine sex in different ways: While some genes play a role in making certain plants male by suppressing female traits, others influence processes like flower development and pollen production. Repetitive sequences of DNA have also expanded over the last 11 million years of evolution, which could explain why the modern chromosome is so massive. X and Y chromosomes often swap DNA with one another, thus allowing them to clean up any accumulated mess, but large regions of the white campion Y don’t recombine at all— causing it to grow bigger and bigger over time.
These results, which were reported in a pair of new Science studies, help illustrate how some plants—most of which are hermaphroditic—evolved to have different sexes. READ THE RELATED SCIENCE PAPER
