Journal Article

The economics of organellar gene loss and endosymbiotic gene transfer

Kelly, Steven

2021

Overview

Background The endosymbiosis of the bacterial progenitors of the mitochondrion and the chloroplast are landmark events in the evolution of life on Earth. While both organelles have retained substantial proteomic and biochemical complexity, this complexity is not reflected in the content of their genomes. Instead, the organellar genomes encode fewer than 5% of the genes found in living relatives of their ancestors. While many of the 95% of missing organellar genes have been discarded, others have been transferred to the host nuclear genome through a process known as endosymbiotic gene transfer. Results Here, we demonstrate that the difference in the per-cell copy number of the organellar and nuclear genomes presents an energetic incentive to the cell to either delete organellar genes or transfer them to the nuclear genome. We show that, for the majority of transferred organellar genes, the energy saved by nuclear transfer exceeds the costs incurred from importing the encoded protein into the organelle where it can provide its function. Finally, we show that the net energy saved by endosymbiotic gene transfer can constitute an appreciable proportion of total cellular energy budgets and is therefore sufficient to impart a selectable advantage to the cell. Conclusion Thus, reduced cellular cost and improved energy efficiency likely played a role in the reductive evolution of mitochondrial and chloroplast genomes and the transfer of organellar genes to the nuclear genome.

• Publisher: BioMed Central,Springer Nature B.V,BMC
• Subject: Animal Genetics and Genomics / Arabidopsis - genetics / Bacteria - genetics / Bioinformatics / Biomedical and Life Sciences / Cell Nucleus / Chloroplast / chloroplast genome / Chloroplasts / Copy number / DNA damage / economics / Endosymbiosis / Energy / energy efficiency / Evolution / Evolutionary Biology / Evolutionary genetics / gene deletion / Gene expression / Gene loss endosymbiotic gene transfer / Gene transfer / Gene Transfer, Horizontal / Genetic engineering / Genome, Chloroplast / Genome, Mitochondrial / Genome, Plant / Genomes / Host Microbial Interactions - genetics / Human Genetics / Hypotheses / Life Sciences / Microbial Genetics and Genomics / Mitochondria / Mitochondria - genetics / Mitochondrion / nuclear genome / Nuclear transfer / Organellar genome / Organelles / Plant Genetics and Genomics / Progenitor cells / Proteins / Proteomics / Retention / symbiosis / Symbiosis - genetics