Figure 1.

DNA damage, chromosome asynapsis and/or unrepaired meiotic DSBs do not induce apoptosis in the male germ line. (A) Cartoon of hermaphrodite (left) and male (right) germ lines. Distal end is capped by somatic distal tip cell(s) and contains a stem cell population of proliferating germ cells (black). Hermaphrodites produce sperm (small dark grey) during larval stages and then switch to oogenesis as adults. Germ cells move towards the proximal gonad where they enter meiotic prophase in the transition zone (leptotene/zygotene; grey crescents) and then progress through pachytene and diplotene (grey circles). In the proximal gonad germ cells are in diakinesis and are packaged into oocytes (dark grey). Apoptosis occurs during the pachytene stage of oogenesis mainly in the gonad loop region (apoptosis zone; circled grey cells). In the male gonad, germ cells differentiate into spermatocytes (grey triangles) and then sperm (dark grey circles); no apoptosis occurs. (B) Number of apoptotic nuclei per gonad arm measured by AO staining 24h post L4 stage (and 24 h post IR). The number of germ lines scored for each genotype is in parenthesis. The data shown are means ± S.E.M. Statistical comparisons between the mutants and wild type were conducted using the two-tailed Mann-Whitney test and all differed significantly (p<0.001) except (*) where p>0.05. (C) TUNEL staining of wild-type and nuc-1 hermaphrodite and male germ lines in the presence and absence of IR. The gonads are outlined in white and show the pachytene region. All panels oriented with distal to left (*). Arrowheads mark some of the white, TUNEL-positive nuclei. Scale bar, 20μm.