Variation within and among species in gene expression: raw material for evolution.

Area of Science:

• Evolutionary biology
• Genomics
• Molecular biology

Background:

• Heritable variation in DNA sequences drives evolution.
• Microarrays enable the study of gene expression variation within and across species.
• Gene expression variation is a key factor in evolutionary processes.

Purpose of the Study:

• To review and synthesize current understanding of gene expression variation and its evolutionary implications.
• To examine the precision of microarray-based gene expression measurements.
• To identify limitations in current evolutionary analyses of gene expression.

Main Methods:

• Review of existing literature on microarray-based gene expression studies.
• Analysis of factors contributing to inter-individual gene expression variation (genetic vs. non-genetic).
• Examination of evolutionary forces (neutral drift, stabilizing selection, directional selection) acting on gene expression.

Main Results:

• Microarray measures of gene expression are precise with proper experimental design.
• Gene expression variation has a substantial heritable component.
• Neutral evolutionary divergence in gene expression is nonlinear over longer timescales due to functional constraints.
• Neutral drift and stabilizing selection are primary drivers of variation among populations and species.

Conclusions:

• Gene expression variation is a critical area for evolutionary research, offering insights into regulatory variation.
• Current studies often overlook the ecological context and assume linear relationships in evolutionary divergence.
• Future research should incorporate ecological factors and test explicit hypotheses regarding gene expression evolution.