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Following the Dynamics of Structural Variants in Experimentally Evolved Populations
Published on: February 3, 2023
Pervasive purifying selection characterizes the evolution of I2 homologs
Brett C Couch1, Russ Spangler, Christine Ramos
1Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota 55108, USA.
Molecular Plant-Microbe Interactions : MPMI
|March 31, 2006
Summary
The Solanum I2 disease resistance gene family diversified over 14 million years in Solanaceae plants. Its slow evolution suggests natural plant R gene diversity offers durable disease resistance.
Area of Science:
- Plant genetics and genomics
- Evolutionary biology
- Molecular plant pathology
Background:
- Disease resistance (R) genes are crucial for plant immunity.
- The Solanum I2 gene family, within the Solanaceae, plays a role in disease resistance.
- Understanding R gene evolution aids in developing durable crop protection strategies.
Purpose of the Study:
- To investigate the evolutionary history and selection patterns of the Solanum I2 gene family.
- To analyze the nucleotide binding site (NBS) region of the I2 gene across diverse Solanaceae species.
- To identify evolutionary mechanisms driving R gene diversity and their implications for resistance durability.
Main Methods:
- Sequencing of 384 I2 gene fragments from six Solanaceae species (potato, S. demissum, tomato, eggplant, pepper, tobacco).
- Phylogenetic analysis to assess evolutionary relationships.
- Selection analyses on the NBS region to detect purifying and positive selection.
- Modeling of gene family evolution using birth-and-death processes.
Main Results:
- The I2 gene family has diversified within Solanaceae for at least 14 million years.
- Gene family evolution follows a slow birth-and-death model, with homogenization taking ~12 million years.
- Strong purifying selection acts on NBS codon positions and lineages.
- Nine codon positions show significant positive selection, and six pairs exhibit correlated amino acid substitutions.
Conclusions:
- Evolutionary analyses of R genes are valuable bioinformatic tools for identifying novel resistance specificities.
- The slow evolutionary rate of I2 genes suggests NBS-leucine rich repeat-mediated resistance may be durable.
- Natural R gene diversity represents a significant resource for developing long-lasting crop disease resistance.
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