Mitochondrial divergence between slow- and fast-aging garter snakes.

Area of Science:

• Evolutionary Biology
• Genomics
• Gerontology

Background:

• Mitochondrial function is a key factor in aging, with declining efficiency and increased free radical production implicated.
• Understanding mitochondrial genotype and phenotype evolution is crucial, especially in species with adaptable physiology.
• Garter snake ecotypes offer a unique model due to divergent aging rates and lifespans despite geographical proximity.

Purpose of the Study:

• To investigate mitochondrial genome-types and transcription in garter snake ecotypes with differing aging rates.
• To identify genetic and regulatory elements within the mitochondrial genome.
• To assess divergence in mitochondrial gene expression and protein-coding regions between slow-aging (SA) and fast-aging (FA) ecotypes.

Main Methods:

• Reconstruction of the garter snake mitochondrial genome sequence using RNA-sequencing (RNA-seq) data.
• Bioinformatic identification of regulatory elements, including a glucocorticoid response element (GRE).
• Analysis of mitochondrial gene expression divergence between ecotypes and under heat stress.
• Sequencing of mitochondrial protein-coding regions to identify genetic variations.

Main Results:

• Two mitochondrial control regions were identified, one containing a GRE.
• Higher gene expression of protein-coding genes was observed in FA snakes compared to SA snakes.
• SA and FA ecotypes exhibited unique mitochondrial haplotypes with amino acid substitutions in CYTB and ND5.
• A significant CYTB amino acid change (Isoleucine to Threonine) was highly segregated between ecotypes.

Conclusions:

• Divergent mitochondrial haplotypes in SA and FA garter snake ecotypes correlate with differences in mitochondrial function.
• These genetic divergences in mitochondria, particularly in CYTB and ND5, may underlie the observed variations in aging rates.
• Mitochondrial genetic makeup plays a significant role in the evolution of aging and lifespan.