The fundamental mechanisms of reproduction and survival are being explored through the analysis of genetic stocks that have reduced fertility and postponed senescence.
age-1(
hx546) is a recessive mutant allele that results in an average 40% increase in life span at 20 C and an average 65% increase at 25 C. Mutant males also show extended life spans. Associated with the increased life span is a 75% decrease in hermaphrodite self-fertility (Friedman and Johnson, Genetics 118: 75-86, 1987). The long-lived phenotype was not separable from
fer-15(
b26), a temperature-sensitive locus on linkage group II causing defective spermatogenesis. It was not clear whether
age-1 was a further mutation in
fer-15 or just tightly linked to fer- 15. We now have three separate lines of evidence to show (1) that age- 1 and
fer-15 are distinct genetic loci and (2) that the decrease in self-fertility is due to
fer-15, not
age-1 as had previously been assumed. Multifactor Crosses: In recombinants selected between
dpy-10 and unc- 4, the decreased self-fertility cosegregates with
fer-15 but long life span does not. We have therefore separated lines with (1) wild-type life span and wild-type self-fertility, (2) wild-type life span and decreased self-fertility, (3) long life span and decreased self- fertility, and (4) long life span and wild-type self-fertility. Deficiency Analysis: Using a series of deficiencies covering much of the region between
dpy-10 and Unc-4, the decreased self-fertility phenotype was assigned to the same region as were
fer-15 and
emb-27. The long life span phenotype was not assigned to this same region, but rather to a region between
let-23 and
unc-4. We are mapping
age-1 more precisely using a second set of deficiencies through this region. Tc1 Recombinants: A Bristol/Bergerac congenic was constructed in which the Bergerac wild-type alleles of
fer-15 and
age-1, together with several centiMorgans of flanking DNA containing many Tc1 elements, have been introgressed into an otherwise Bristol (N2) genetic background. Recombinants of this congenic crossed with a
dpy-10 age-1 ere chosen. We then assayed their Tc1 patterns, temperature-sensitive defective spermatogenesis, self-fertility, and life span.
fer-15 and decreased self-fertility cosegregated and mapped to the middle of the region containing novel Tc1 bands. Life span (
age-1) mapped further to the right, closer to
unc-4. These three lines of evidence provide a consistent interpretation of the relationship between
fer-15 and
age-1. These are two separate, closely linked genes.
fer-15(
b26) is responsible for both temperature- sensitive defective spermatogenesis and decreased self-fertility. age- 1
(hx546) is responsible for long life span. We have identified the location of
fer-15 on the physical map by deletion mapping (see Tedesco & Johnson). The location of
age-1 will be identified through the mapping of Tc1 and Non-Tc1 polymorphisms in the Tc1 recombinants described above. The actual cloning of the genes will involve transformation of mutants with the wild-type alleles and sequence analysis to identify the mutational events responsible for the alteration of fertility and life span.