lewisii (A) does not express yellow pigment and has intermediate levels of red. H gives the species name, which gene variants it has, whether yellow pigment is present, and whether it has high, intermediate, or low levels of red pigment. A-G each show a picture of a monkeyflower face on, then its cross-section, then an extraction of its pigments in a test tube.
The image shows closely related species of monkeyflowers (Mimulus) with varied versions of genes that cause them to express different amounts of yellow (carotenoid) and red (anthocyanin) pigments. The uniqueness of these three genes, only found in a few closely related monkeyflowers, is an important clue as to how new species evolve.
Not only does YUP regulate a gene it is entirely unrelated to it the other two genes at this same locus also affect monkeyflower color, Yuan says. “This experience really taught me how important it is not to constrain oneself with ‘conventional wisdom,’” Yuan says. There are very few examples of genes that produce small RNAs affecting traits important to the creation of a new species. YUP produced many small RNAs that suppressed the carotenoid gene. But Liang’s persistence paid off: she discovered that the YUP gene was actually targeting the plants’ master regulator of carotenoids, the pigments that make monkeyflowers and other plants yellow. Liang decided to investigate what these genes were doing anyway, against the advice of Yuan, who thought it was a waste of time. Standard genetics thought is that partial duplicate genes regulate the genes they are derived from it was very unlikely that these genes would affect an unrelated gene. In particular, YUP is a partial duplicate of a pre-existing gene that has nothing to do with color. They are duplicates of other genes from other parts of the monkeyflower genome. These new genes are not found in species outside of this group. The YUP gene in question is found at a locus, or region, of the monkeyflower genome that has three new genes. Their research adds weight to a theory that new genes create diversity of appearance and even new species. UConn botanist Yaowu Yuan, an associate professor in the Department of Ecology and Evolutionary Biology, and postdoctoral researcher Mei Liang (currently a professor at South China Agricultural University), with collaborators from four other institutes, have now shown exactly which gene it is that changed to prevent monkeyflowers from making yellow. Instead, hummingbirds pollinated it, isolating the red flowers genetically and creating a new species. Later, a descendent species accumulated mutations in a gene called YUP that recovered the yellow pigments and led to production of red flowers. In this case, a monkeyflower species lost the yellow pigments in the petals but gained pink about 5 million years ago, attracting bees for pollination. And monkeyflowers provide a textbook example of how a single-gene change can make a new species. They are also famously diverse in shape and color. Monkeyflowers are famous for growing in harsh, mineral-rich soils where other plants can’t. These mimulus flowers at the EEB research greenhouses, show a great diversity of colors that contribute to pollinator preference and speciation. 10 issue of Science, UConn botanists explain what happened genetically to jettison the yellow pigment, and the implications for the evolution of species. But about 5 million years ago, some of them lost their yellow. Monkeyflowers glow in a rich assortment of colors, from yellow to pink to deep red-orange.
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