Do mosses get Alzheimer's?

A protein central to amyloid plaque formation in the brain, a condition that causes or contributes to Alzheimer’s disorder (not disease, which refers to an infection by organisms), has been found in a moss (link to news article). Clearly the same gene has two different functions.

When this protein is deactivated in moss, the moss’ growth form becomes abnormal, and when the human gene is inserted, the moss returns to its normal form. The last common ancestor between the lineage containing mosses (land plants) and the lineage including humans (animals) must date to more than 2 billion years ago when early eukaryotes were diversifying. And yet this gene has been conserved, undergone so little changes since, that the human protein remains functional in the moss.

Now the exciting news from a botanical perspective is that a bryologist has an angle to get their hands on some NIH funding. Move over neurobiologists, here come the bryologists!

But this is an interesting example of another widely misunderstood biological phenomenon. When people express their doubts, their incredulity that evolutionary processes can account for all the observed diversity and innovation, they only express a naïve perspective. Close inspection of diversity demonstrates precious little real innovation, and a great deal of recycling. Very similar and nearly identical “parts” can take on whole new functions and used in completely different ways, just as a wheel on an axil can have many functions in a vehicle. The raw material of evolutionary processes are slight variations in the genetic instructions of organisms. And it will be interesting to try to figure out why a protein with two such different functions nonetheless was conserved in very nearly identical forms.