A direct experimental test of Ohno's hypothesis

Area of Science:

• Evolutionary biology
• Molecular evolution
• Genetics

Background:

• Gene duplication is a key driver of evolutionary innovation, providing new genetic material for novel protein functions.
• Ohno's hypothesis suggests gene duplication facilitates new phenotypes by allowing genes to tolerate mutations.
• Competing theories propose that deleterious mutations rapidly inactivate gene duplicates, limiting their evolutionary potential.

Purpose of the Study:

• To experimentally test Ohno's hypothesis on gene duplication and evolution.
• To investigate the impact of gene copy number on evolutionary dynamics and mutational robustness.
• To explore the role of gene dosage in the evolution of new phenotypes.

Main Methods:

• Evolving populations of Escherichia coli with either one or two copies of a fluorescent protein gene.
• Employing high-throughput DNA sequencing to analyze genotypic evolution.
• Utilizing biochemical assays and engineering of selected variants to assess phenotypic changes.

Main Results:

• Populations with two gene copies exhibited greater mutational robustness compared to single-copy populations.
• Double-copy populations showed relaxed purifying selection, increased genetic and phenotypic diversity, and earlier accumulation of beneficial mutations.
• Despite increased diversity, phenotypic evolution was not accelerated, potentially due to rapid inactivation of one gene copy.

Conclusions:

• Experimental results support Ohno's hypothesis regarding increased mutational robustness from gene duplication.
• Findings suggest that gene dosage plays a crucial role, potentially offering an alternative explanation to Ohno's original hypothesis.
• The study provides a valuable experimental framework for testing models of evolution by gene duplication.