More about how evolution works: multicellularity (Evolution)

by David Turell , Monday, November 02, 2015, 15:04 (3097 days ago) @ David Turell

Multicellularity appeared independently a few times, but genetic studies suggest the gens for it were present in the single cells:-http://www.the-scientist.com/?articles.view/articleNo/30827/title/From-Simple-To-Complex/-"As some of the most ancient animals, sponges can provide information regarding the evolution of the metazoan lineage, but for true insights about the origin of multicellularity, scientists must look even further back on the evolutionary tree. Choanoflagellates, unicellular organisms that look remarkably similar to the feeding structures of sponges, are the closest living relatives of metazoans. It turns out that they also share a number of genes once thought to be unique to multicellular animals. Tyrosine kinases (TK), for example, enzymes that function in cell-cell interactions and regulation of development in animals, were identified in the choanoflagellates in the early part of this decade, and the first sequenced choanoflagellate genome, published in 2008, revealed that they have more TK genes than any animal—and many other components of the TK signaling pathway as well.-"As some of the most ancient animals, sponges can provide information regarding the evolution of the metazoan lineage, but for true insights about the origin of multicellularity, scientists must look even further back on the evolutionary tree. Choanoflagellates, unicellular organisms that look remarkably similar to the feeding structures of sponges, are the closest living relatives of metazoans. It turns out that they also share a number of genes once thought to be unique to multicellular animals. Tyrosine kinases (TK), for example, enzymes that function in cell-cell interactions and regulation of development in animals, were identified in the choanoflagellates in the early part of this decade, and the first sequenced choanoflagellate genome, published in 2008, revealed that they have more TK genes than any animal—and many other components of the TK signaling pathway as well.-***-"The genomic exploration of the evolution of multicellularity is really just beginning, but already, a trend is emerging. “Almost every month now we are seeing genes that were supposed to be exclusive to metazoans that are already present in their single-cell relatives,” says evolutionary biologist Iñaki Ruiz-Trillo of the University of Barcelona. “I think that means co-option of ancestral genes into new functions is important for evolutionary innovations like the origin of multicellularity.”-“'Probably the more data we collect, the fewer and fewer animal-specific genes there are going to be,” agrees Dunn. “And we're going to have to explain the origins of multicellularity in terms of changes in the way these gene products interact with each other.”-***-"Animals aren't the only multicellular organisms, of course, and thus not the only system applicable to the study of multicellularity's origins. In fact, multicellularity is believed to have evolved as many as 25 different times among living species. So while the search for metazoan origins may be riddled with uncertainty, perhaps scientists can draw inferences from the study of multicellularity in other lineages."-Comment: Very long and complex article. Looks like pre-planning to me. The discussion about supposed cooperation and conflict between cells as multicellularity develops makes me wonder what the author was smoking.