Hello Nature readers,
Today we discover the unusual mathematics that gives rose petals their shape, learn about a new technique to directly edit proteins in living cells and recall how India rewrote the rules of space travel when it launched its first satellite.

A rose by any other geometry

The curled edges and pointed corners of rose petals form thanks to a geometric trick never before observed in nature. Using a combination of theoretical analysis, simulations and good old plastic sheets, physicists found that a type of mechanical feedback regulates the petals’ growth as they curl outwards. This feedback relies on 3D, or ‘extrinsic’ geometries, which push the edges of the petal into curls. The petal’s edge can’t form a single curl, so it forms multiple ones with cusps in between. As the petal continues to grow outwards, mechanical stresses at each cusp begin to turn what was a round edge into an angle.

New method edits proteins in living cells

A new technique can directly edit proteins in living cells. The method relies on strings of amino acids called inteins, which can cut themselves out of proteins autonomously. So far, scientists have used inteins to splice unusual amino acids and even larger chains called polymers into proteins, and can observe how such additions affect a protein’s function and location. The process is “cut and paste”, says biochemist and study co-author George Burslem: inteins eject from a protein, leaving a gap. Then, the desired molecule to be spliced in — also bracketed by inteins — is ejected from a ‘donor’ protein and slots into its place.

Birdwatcher app reveals where birds thrive

North American bird populations are declining most severely in areas where they should be thriving. Nevertheless, most species had pockets where their populations were growing. Researchers analysed 36 million birdwatchers’ observations shared using the Cornell Lab of Ornithology’s eBird app, alongside satellite data, to give unprecedented insights. “The locations where these species were thriving in the past, where the environments were really well suited to birds, are now the places where they are suffering the most,” says ecological statistician and co-author Alison Johnston. “The way I interpret this result is that it’s indicative of major changes in our world.”

How India’s first satellite rewrote the rules

Fifty years ago, India launched a satellite that redefined what a low-income country could achieve, writes science historian Pranav Sharma. The satellite, named Aryabhata after an ancient Indian astronomer, was launched with the help of the Soviet Union. “When the Kosmos-3M rocket roared to life, it carried not just circuitry but also the dreams of a nation not even 30 years free from colonial rule,” notes Sharma. India’s space programme would become the envy of the world for its ability to operate on a shoestring budget.

Futures: Romeo and the robots

Two households, both alike in dignity, begin their feud anew in the latest short story for Nature’s Futures series.

Podcast: Will US science survive Trump 2.0?

US president Donald Trump and his administration have gutted science agencies, terminated research programmes and cancelled billions of dollars in grants to universities. In this week’s episode, Nature reporter Jeff Tollefson joins the Nature Podcast to explore the long-term impacts for the United States and the world. (Nature | 14 min read)