Genome Tree of Life: Deep Burst of Organism Diversity

An organism Tree of Life (organism ToL) is a conceptual and metaphorical tree to capture a simplified narrative of the evolutionary course and kinship among the extant organisms of today. Such tree cannot be experimentally validated but may be reconstructed based on characteristics associated with the extant organisms. Since the whole genome sequence of an organism is, at present, the most comprehensive descriptor of the organism, a genome Tol can be an empirically derivable surrogate for the organism ToL. However, a genome ToL has been impossible to construct because of the practical reasons that experimentally determining the whole genome sequences of a large number of diverse organisms was technically impossible. Thus, for several decades, gene ToLs, based on selected genes, have been commonly used as a surrogate for the organisms ToL. This situation changed dramatically during the last several decades due to rapid advances in DNA sequencing technology. Here we describe the main features of a genome ToL that are different from those of the broadly accepted gene ToLs: (a) the first two organism groups to emerge are the founders of prokarya and eukarya, (b) they diversify into six large groups and all the founders of the groups have emerged in a “Deep Burst” at the very beginning period of the emergence of Life on Earth and (c) other differences are notable in the order of emergence of smaller groups.Significance StatementTree of Life is a conceptual and metaphorical tree that captures a simplified narrative of the evolutionary course and kinship among all living organisms of today. Since the whole genome sequence information of an organism is, at present, the most comprehensive description of the organism, we reconstructed a Genome Tree of Life using the proteome information from the whole genomes of over 4000 different living organisms on Earth. It suggests that (a) the first two primitive organism groups to emerge are the founders of prokarya and eukarya, (b) they diversify into six large groups, and (c) all the founders of the groups have emerged in a “Deep Burst” at the very beginning period of the emergence of Life on Earth.