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...
