Every organism today originates from a single shared ancestor, the "last universal common ancestor" (LUCA), which lived approximately four billion years ago. LUCA possessed established features such as cell membranes and DNA-based genetic information, indicating that the origins of life predate this organism.
Unveiling Pre-LUCA Evolution
A study published in Cell Genomics by Aaron Goldman (Oberlin College), Greg Fournier (MIT), and Betül Kaçar (University of Wisconsin-Madison) describes a method to explore evolution before LUCA. The researchers focus on "universal paralogs," a specific group of genes that retain evidence of biological changes occurring prior to LUCA.
What Are Universal Paralogs?
Paralogs are related genes found multiple times within a single genome, such as the eight human hemoglobin genes. Universal paralogs are distinct because they appear in at least two copies in the genomes of almost all living organisms.
This widespread presence suggests their initial duplication predates LUCA, and these duplicated genes have been passed down through generations.
The Significance of Universal Paralogs
The authors consider universal paralogs a critical resource for studying Earth's earliest life history. Advances in AI-based techniques and hardware are making the detailed analysis of ancient genetic patterns more feasible.
Goldman states that universal paralogs provide significant information about life before LUCA.
Fournier emphasizes the importance of extracting knowledge from these genes, as they are the only available information regarding early cellular lineages.
Early Cellular Insights
Core Functions Identified
Analysis of known universal paralogs by Goldman, Fournier, and Kaçar revealed their involvement in either protein synthesis or molecule transport across cell membranes. This finding suggests that protein production and membrane transport were among the earliest biological functions to evolve.
Reconstructing Ancient Proteins
Research from Goldman's lab at Oberlin involved reconstructing the protein produced by an original ancestral gene from a universal paralog family. This family is involved in inserting enzymes and other proteins into cell membranes. The reconstructed ancient protein retained the ability to attach to cell membranes and interact with protein-making machinery, providing insights into the operations of the earliest cells.
The Path Forward
Researchers express hope that advancements in computational tools will enable the identification of additional universal paralog families and more detailed study of their ancient ancestors.
Kaçar indicates that universal paralogs offer a connection between the earliest stages of life and modern scientific tools, allowing for testable discoveries and a clearer understanding of evolution before LUCA.