JohnFByers t1_it1kqlg wrote
Reply to comment by eniteris in Novel multicellular prokaryote discovered next to an underground stream by eniteris
Temporal and spatial regulation of gene expression that generates cell lineages comprising interdependent cells with a common genome. Among the metazoans, Porifera have a totipotent and rudimentary stem cell system that still provides mechanisms of development and differentiation. Transdifferentiation remains differentiation and I just see it as the basis of cellular plasticity.
Having dabbled in PDZ domains (before they were named PDZ domains and we just called them discs-large-like domains), I was pleasantly surprised to see recently the discovery of essentially intact post-synaptic density components in a multicellular eukaryote lacking a nervous system — the signalling and scaffolding components were there nonetheless.
Granted, other mechanisms of cell signalling exist that do not rely on animal-style junctions. But the other criteria remain challenging. If we do impose a common genome limitation, which I am convinced is appropriate, then prokaryotes with their relatively widespread propensity toward lateral gene transfer will be even more challenging to accept as anything beyond colonial.
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