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Genetic structure and evolution of RAC-GTPases in Arabidopsis thaliana
P Winge1, T Brembu, R Kristensen
1UNIGEN Center for Molecular Biology and Department of Botany, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
Genetics
|December 5, 2000
Summary
Plant RAC proteins, key regulators of cell functions, evolved rapidly before land plants emerged. Arabidopsis thaliana has 11 RAC genes, with some unique to vascular plants, suggesting adaptation and diversification.
Area of Science:
- Molecular Biology
- Plant Science
- Genomics
Background:
- Rho GTPases are crucial eukaryotic regulators of cytoskeleton organization, signal transduction, and cell growth.
- The Ras superfamily of GTPases includes Rho proteins, vital for cellular processes.
- Land plants (embryophytes) possess Rho family proteins homologous to RAC-like proteins.
Purpose of the Study:
- To present genomic and cDNA sequences of the RAC gene family in Arabidopsis thaliana.
- To analyze the evolution and diversification of plant RAC genes.
- To investigate the expansion of RAC genes in embryophytes via gene duplication.
Main Methods:
- Extensive gene screening, characterization, and analysis.
- Amino acid alignment and genomic structure comparison.
- Phylogenetic analysis of RAC gene families.
Main Results:
- Identified 11 AtRAC proteins in Arabidopsis thaliana, divided into two distinct groups.
- One RAC group appears exclusive to vascular plants.
- Phylogenetic analysis indicates rapid RAC gene evolution before embryophyte emergence, distinct from other eukaryotes.
- RAC genes expanded in embryophytes through large gene duplications, with five reported in Arabidopsis.
- Hypothesized that plant RAC proteins compensate for the loss of RAS proteins.
Conclusions:
- Plant RAC genes exhibit unique evolutionary trajectories, diverging significantly from other eukaryotes.
- Gene duplication events have driven the expansion and diversification of RAC genes in land plants.
- AtRAC proteins likely play specialized roles in higher plants, potentially compensating for ancestral RAS protein functions.