Polymorphism in the rDNA origin of replication mediates replicative lifespan.

<p>(A) A schematic of rDNA elements and identified polymorphisms, not drawn to scale. Locations of sequence differences between the RM and BY rDNA are noted with asterisks (*). (B) Wild yeast isolates DBVPG6765, L_1374, and Y12 have RM rDNA sequences with the single BY RFB or BY rARS polymorphisms. rDNA from each of these wild strains was backcrossed into the BY background and lifespan analysis was performed on each (n = 40 cells). The mean replicative lifespan for each strain is indicated in parentheses. rDNA loci from DBVPG6765 and L_1374 confer significant lifespan extension (<i>P</i> = 10⁻⁴, ν = 2) while the Y12 rDNA locus does not (<i>P</i> = 1.4×10⁻¹, ν = 2).