Evolution: studies of multicellularity origin (Evolution)

by David Turell , Wednesday, February 21, 2024, 18:07 (274 days ago) @ David Turell

From an interview:

https://www.quantamagazine.org/a-multitalented-scientist-seeks-the-origins-of-multicell...

"I provided direct experimental evidence for something that had long been hypothesized, but not previously shown. Namely, that just as whole animals can be subject to natural selection, where the fit survives better than the less fit, individual germ cells within a developing animal can do the same thing.

"Germ cells are fascinating because they are a special novelty of multicellular organisms. Almost every major successful multicellular life form reproduces with germ cells. They are how genes get passed down from one generation to another. They are what provides the ability for cells to stick together, or to form a big multicellular conglomerate like a banana or a person.

***

"Much of my subsequent career has been guided by wanting to understand how a single cell, the fertilized egg, creates a complex multicellular adult made of millions of cells. I’m trying to figure out how the different types of cells in organisms first arose.

"Among the questions I’m asking is: How do they know what to do? What genes do they use to do this? And since the first life on Earth was single-celled, how did multicellular genes and cell types evolve in the first place?

***

"First, showing that cell-cell signaling is not an unusual way for animals to generate embryonic germ cells — that is, cells that will become eggs and sperm. The idea that dominated textbooks for most of the 20th century was that in insects and most other animals, a “germ plasm” in the egg established a distinct lineage of germ cells very early in development. But we showed that in crickets, body cells are induced to change into germ cells by signals from the surrounding tissues. That’s what happens in mice and other mammals, too, but it was thought to be a novel mechanism that appeared rarely in evolution.

"Second, discovering in 2020 that the long-lost relatives of oskar, a gene very famous for its essential role in insect reproduction, were actually from bacteria, not just from earlier animals. This gene evolved by fusion of bacterial genome sequences with animal genome sequences. It suggests that the forerunners to oskar had very different functions, possibly in the development of the nervous system, and that further study of how it evolved its new purpose could be highly informative." (my bold)

Comment: bacteria are at work and helpful in every stage of life.