Divergence in expression between duplicated genes in Arabidopsis

Area of Science:

• * Evolutionary genetics
• * Molecular biology
• * Plant genomics

Background:

• * New genes arise from various duplication events like tandem duplication, dispersed duplication, and polyploidy.
• * Patterns of divergence between duplicated genes can differ based on their origin.
• * Understanding gene duplication is crucial for comprehending genome evolution and functional diversification.

Purpose of the Study:

• * To investigate patterns of gene expression and coding sequence divergence in duplicated genes in Arabidopsis thaliana.
• * To compare divergence patterns between polyploidy-derived, tandem, and dispersed gene duplicates.
• * To explore the relationship between expression divergence and sequence divergence, and the role of purifying selection.

Main Methods:

• * Analysis of gene expression patterns and coding sequence divergence in duplicated gene pairs in Arabidopsis thaliana.
• * Comparison of divergence rates across different gene duplication types (polyploidy, tandem, dispersed).
• * Statistical analysis to assess the correlation between expression divergence and sequence divergence (synonymous and nonsynonymous substitutions).

Main Results:

• * Divergence in expression profiles occurs early, near the time of duplication, for tandem and dispersed duplicates.
• * A strong positive relationship exists between expression divergence and nonsynonymous substitutions, but not synonymous substitutions, contrary to other eukaryotes.
• * Polyploidy-derived duplicates show broader expression patterns and higher expression levels.
• * Purifying selection on protein sequence and expression patterns appears to be correlated, especially in polyploidy-derived pairs.
• * The subfunctionalization model partially explains duplicate gene preservation, as one gene is often expressed at a higher level.

Conclusions:

• * The correlation between expression divergence and nonsynonymous substitutions suggests a link between protein sequence evolution and gene regulation.
• * Purifying selection plays a significant role in maintaining both protein function and expression patterns of duplicated genes.
• * Differences in expression and divergence patterns highlight distinct evolutionary trajectories for genes arising from different duplication mechanisms.
• * The subfunctionalization model alone is insufficient to explain all observed patterns of duplicate gene expression divergence.