Australasian Science: Australia's authority on science since 1938

A Protein Is Born

Cover of the March 2014 edition of Plant Cell. Artwork by Scot Nicholls, Domokun

Cover of the March 2014 edition of Plant Cell. Artwork by Scot Nicholls, Domokun Design.

By Joshua Mylne

It used to be thought that new proteins only evolved as a result of gradual changes to existing genes, but recent studies are showing that completely new genes and proteins often evolve suddenly. Now Australian researchers have predicted the biochemical events that allowed an enzyme-blocking protein to evolve “from scratch” in sunflowers.

The full text of this article can be purchased from Informit.

Each genome and the proteins it encodes is what makes every organism unique. Although it has been known for a long time that genes can appear suddenly in some species or change their sequence and code completely different proteins, it now seems that this is far more common than anyone expected. Some people are even saying that genes or proteins that appear de novo are the major driver of biological innovation.

Most de novo gene studies focus on DNA and the new messages that come from them, but we’ve been looking downstream at a very specific example of de novo protein evolution.

The common sunflower has an unusual gene called PawS1 whose encoded protein is processed into a storage albumin protein. Buried alongside albumin in the PawS1 protein is a second, completely different protein that blocks digestive enzymes.

Seed storage albumins are made in great abundance to serve as a degradable source of nitrogen and sulfur for germinating seeds. By contrast, digestion-blocking proteins protect seeds from grain-eating insects.

We were desperate to know how such different proteins ended up being cut from the same precursor protein. By tracing the evolutionary history of PawS1, we could predict which steps enabled PawS1 to make two proteins instead of just the usual one.

Gene Duplication and Divergence

The panapoly of proteins in each...

The full text of this article can be purchased from Informit.