Biosystems
Volume 202, April 2021, 104371
Is it possible that cells have had more than one origin?
Sávio Torres de Farias a, b Marco V. Jose c, Francisco Prosdocimi c, d
a Laboratório de Genética Evolutiva Paulo Leminski, Centro de Ciências Exatas e da Natureza, Universidade Federal da Paraíba, João Pessoa, Paraíba, Brazil
b Network of Researchers on the Chemical Evolution of Life (NoRCEL), Leeds, LS7 3RB, UK
c Theoretical Biology Group, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, D.F. C.P. 04510, México, USA
d Laboratório de Biologia Teórica e de Sistemas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
Received 23 December 2020, Revised 22 January 2021, Accepted 22 January 2021, Available online 30 January 2021.
Abstract
Cells occupy a prominent place in the history of life in Earth. The central role of cellular organization can be understood by the fact that “cellular life” is often used as a synonym for life itself. Thus, most characteristics used to define cell overlap with those ones used to define life. However, innovative scenarios for the origin of life are bringing alternative views to describe how cells may have evolved from the open biological systems named progenotes. Here, using a logical and conceptual analysis, we re-evaluate the characteristics used to infer a single origin for cells. We argue that some evidences used to support cell monophyly, such as the presence of elements from the translation mechanism together with the universality of the genetic code, actually indicate a unique origin for all “biological systems”, a term used to define not only cells, but also viruses and progenotes. Besides, we present evidence that at least two biochemical pathways as important as (i) DNA replication and (ii) lipid biosynthesis are not homologous between Bacteria and Archaea. The identities observed between the proteins involved in those pathways along representatives of these two ancestral domains of life are too low to indicate common genic ancestry. Altogether these facts can be seen as an indication that cellular organization has possibly evolved two or more times and that LUCA (the Last Universal Common Ancestor) may not have existed as a cellular entity. Thus, we aim to consider the possibility that different strategies acquired by biological systems to exist, such as viral, bacterial and archaeal were most likely originated independently from the evolution of different progenote populations.
Keywords
Monophyly Progenotes Membrane evolution Origin of biological systems
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