Different stresses affect telomere length via different genes.

<p>The effect of ethanol, caffeine and high temperature on telomere length was tested on strains carrying individual gene deletions/hypomorphic mutations. Each mutant was grown under the relevant stress for 100 generations and its telomere length was measured using Southern blot analysis. <b>A–C</b>. The X-axis shows the initial length of each mutant and the Y-axis shows the elongation or shortening after 100 generations. Each strain analyzed is represented by a circle (wt in green). A strong correlation (demarked by a red line; ±5% SD) was seen between the initial length and the effect of the stress. <b>A</b>. Ethanol. <b>B</b>. Caffeine. <b>C</b>. 37°C. <b>D</b>. Each bar represents the ratio between the initial telomere length and the elongation after 100 generations in ethanol. Very short <i>tlm</i> mutants (below 200 nt long) could be clearly separated into two groups: mutants of the Tel1 pathway (<i>tel1Δ</i>, <i>mre11Δ</i>, <i>rad50Δ</i>, <i>xrs2Δ</i>) were highly responsive to ethanol stress, while mutants of the NMD (<i>nam7Δ</i>, <i>upf3Δ</i>, <i>nmd2Δ</i>) and Ku (<i>yku70Δ</i>, <i>yku80Δ</i>) pathways show little telomeric elongation under ethanol stress.