That's why some flowers have many petals


Why are some flowers, to use a famous neologism some time ago, very "petalosis"? This is explained by a recent study published by the State University of Milan, with the Institute of Agricultural Biology and Biotechnology (Ibba) of the Cnr and the Padano Technology Park of Lodi.
The research was published in the Journal of Experimental Botany - "Mutations in orthologous PETALOSA TOE-type genes cause a dominant double-flower phenotype in phylogenetically distant eudicots-, and revealed that the" petalosity "of some flowers (such as roses, carnations, petunias) is due to very similar natural genetic mutations.
This information is of great interest for nursery gardening, always looking for new products to be put on the market. The "double flowers", with increased number of petals, are in fact often preferred by consumers and increase the commercial value of many varieties.
The all-Italian discovery is the result of a collaboration between the State University of Milan, where it was coordinated by Laura Rossini, professor of Agricultural Genetics at the Department of Agricultural and Environmental Sciences, the Institute of Agricultural Biology and Biotechnology of the National Research Council (Cnr-Ibba), with the first author Stefano Gattolin, and the Padano technological park of Lodi (PTP Science Park).
In addition to the laboratory, part of the analyzes were also carried out on the computer, thanks to online databases containing the entire genomic sequence of the DNA of different plants. As for carnation, for example, genetic information of the famous "Francesco" variety, created in the second half of the last century by the renowned Italian hybridizer Giacomo Nobbio, is available online.
Researchers have shown that particular mutations in a key gene of flower development alter its regulation, so as to make it "work" longer and lead precisely to the formation of an abundance of petals compared to the five which would be normal in the carnation and in other species.
During previous studies, the authors had already identified the mutation responsible for this character in the peach tree and in some roses: "It was really surprising to analyze one by one the genes that we believed involved and to gradually find similar mutations in the Rugosa rose, carnations and popular "double" petunias, so much so that we wanted to coin the name Petalosa for the gene family characterized by us ", comments Gattolin. "The transfer of this information to different species was not at all obvious, we think that the plants covered by this study are so different that their common ancestor dates back to the Cretaceous, when the world was still dominated by dinosaurs," says Rossini.
Man, guided by his ideal of aesthetic sense, over the centuries has selected the natural mutations that occurred in the Petalosa genes and thus favored the spread of varieties with spectacular blooms. This knowledge can now be applied to the development of new "double flower" varieties in other plants, also through the new genome editing techniques, which allow specific gene sequences to be modified in a targeted manner.
In the cover photo: In DNA, represented here by the sequence of the four nitrogen bases A, T, G and C, a key sequence (in red) has been identified which, if changed, leads to the multiplication of the petals in petunia, rose, and carnation. Credits: Stefano Gattolin.


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