More about how evolution works: multicellularity (Evolution)

by David Turell , Saturday, February 03, 2018, 01:30 (2484 days ago) @ dhw

The genetic pathway in algae further elucidated:

https://www.sciencedaily.com/releases/2018/02/180202112649.htm

"Tetrabaena is a member of a lineage of green-algae known as the volvocine lineage. The lineage is a model lineage for understanding how multicellularity evolved. By studying the genome of this simple alga, a number of genetic mechanisms that control how cells divide were associated with the origin of multicellularity.

"By painstakingly piecing together the whole genome sequence for the alga over a period of over two years, using various genome-sequencing methodologies, Featherston has identified the ubiquitin proteasomal pathway (UPP) as a process that plays a key role in the evolution of multicellularity. This pathway is involved in regulating many activities in cells by targeting proteins for destruction thereby maintaining a careful balance of proteins in cells.

"'The UPP has been implicated in many human cancers and even as a potential target for treating cancers. From this study it seems that alterations to this pathway were important for how multicellularity evolved in these algae," says Featherston.

"UPP is a complicated pathway that controls the cellular concentration of key proteins that drive cell division and it plays a role in many cellular functions. Featherston's study suggests that UPP may play a regulating how many divisions each species of volvocine undergoes through degradation of key molecules that control cell division.

***

"Featherston's work shows that the evolution of multicellularity is associated with lineage-specific genetic developments.

"Multicellularity has evolved at least 25 times independently, but in all likelihood while certain general biological mechanisms -- like cells-sticking together or modified cell cycles -- may be shared, the actual genes driving these developments will mostly be unique to each lineage," he says. "Almost all the families that are found in other organisms can be found in a diverse array of unicellular organisms, suggesting that the genes that gave rise to multicellularity were derived from genes that were already present in the unicellular ancestor but may have been duplicated to form new genes that now have new functions." (my bold)

Comment: Note my bold. What I am surprised about is that multcellularity is clear evidence of convergence in evolution and I view this as a strong indicator of a drive to complexity as part of the mechanism that drives evolution.