Mild Telomere Dysfunction as a Force for Altering the Adaptive Potential of Subtelomeric Genes

Area of Science:

• Genetics
• Molecular Biology
• Evolutionary Biology

Background:

• Subtelomeric regions possess unique repetitive structures and evolve rapidly.
• These regions are enriched for genes crucial for niche adaptation.
• The adaptive telomere failure hypothesis posits that environmental stress can cause telomere failure, increasing subtelomeric recombination and adaptive mutations.

Purpose of the Study:

• To test if mild telomere dysfunction elevates mutation rates in subtelomeric genes without significantly impacting cell fitness.
• To investigate the specific types of mutations induced by varying levels of telomere dysfunction.

Main Methods:

• Utilized a *Kluyveromyces lactis* mutant with stably short telomeres.
• Analyzed mutations in the subtelomeric β-galactosidase (*LAC4*) gene under conditions of severe and mild telomere dysfunction.
• Characterized mutation types, including base changes and terminal deletion/duplication events.

Main Results:

• Stably short telomeres in *K. lactis* led to a significant increase in *LAC4* gene mutations.
• Severe telomere dysfunction resulted in mutations consistent with break-induced replication (terminal deletion/duplication).
• Mild telomere dysfunction also caused terminal deletion/duplication but, unexpectedly, up to 50% of *LAC4* mutants showed base changes in the coding region.

Conclusions:

• Mild telomere dysfunction can substantially increase subtelomeric gene mutation rates, specifically favoring base changes.
• This provides evidence that subtle telomere dysfunction acts as a mechanism to enhance the adaptive potential of subtelomeric genes.
• The findings support the adaptive telomere failure hypothesis, highlighting a novel pathway for evolutionary adaptation.