Limits...
Male-killing symbiont damages host's dosage-compensated sex chromosome to induce embryonic apoptosis

View Article: PubMed Central - PubMed

ABSTRACT

Some symbiotic bacteria are capable of interfering with host reproduction in selfish ways. How such bacteria can manipulate host's sex-related mechanisms is of fundamental interest encompassing cell, developmental and evolutionary biology. Here, we uncover the molecular and cellular mechanisms underlying Spiroplasma-induced embryonic male lethality in Drosophila melanogaster. Transcriptomic analysis reveals that many genes related to DNA damage and apoptosis are up-regulated specifically in infected male embryos. Detailed genetic and cytological analyses demonstrate that male-killing Spiroplasma causes DNA damage on the male X chromosome interacting with the male-specific lethal (MSL) complex. The damaged male X chromosome exhibits a chromatin bridge during mitosis, and bridge breakage triggers sex-specific abnormal apoptosis via p53-dependent pathways. Notably, the MSL complex is not only necessary but also sufficient for this cytotoxic process. These results highlight symbiont's sophisticated strategy to target host's sex chromosome and recruit host's molecular cascades toward massive apoptosis in a sex-specific manner.

No MeSH data available.


DNA damage in the X chromosome of Spiroplasma-infected male embryos.(a) Simultaneous detection of pH2Av (DNA damage foci or apoptotic nuclei; green), MSL1 (X chromosomes; magenta) and DNA (blue) in an uninfected male embryo at stage 11, wherein few green pH2Av signals are seen. (b,c) Magnified images of boxed regions in a. Single-channelled images of b and c are shown in b′–b′′′ and c′–c′′′, respectively. (d) An image similar to a of an infected male embryo, in which a number of green pH2Av signals are detected. (e,f) Magnified images of boxed regions in d. Single-channelled images of e and f are shown in e′–e′′′ and f′–f′′′, respectively. In d–f, arrowheads indicate large pH2AX signals representing apoptotic nuclei, whereas arrows depict focal pH2AX signals representing DNA damage foci. (g) Quantification of focal pH2AX signals in uninfected and infected embryos at stage 11. Different letters (a,b) indicate statistically significant differences (P<0.05; Kruskal–Wallis test followed by Mann–Whitney U-tests). (h) Quantification of focal pH2AX signals overlapping with MSL1-labelled X chromosomes in uninfected and infected male embryos at stage 11. Asterisks indicate a statistically significant difference (**, P<0.01; Pearson's χ2 test). Focal pH2Av signals obtained in g were used to calculate the enrichment on the X chromosome in h. In g and h, box plots are as in Fig. 2i,j. Sample sizes (numbers of images analyzed) are shown at the bottom. Numbers of embryos inspected are shown in parentheses. Scale bars, 20 μm (a,d) and 5 μm (b–c′′′,e–f′′′).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5036004&req=5

f3: DNA damage in the X chromosome of Spiroplasma-infected male embryos.(a) Simultaneous detection of pH2Av (DNA damage foci or apoptotic nuclei; green), MSL1 (X chromosomes; magenta) and DNA (blue) in an uninfected male embryo at stage 11, wherein few green pH2Av signals are seen. (b,c) Magnified images of boxed regions in a. Single-channelled images of b and c are shown in b′–b′′′ and c′–c′′′, respectively. (d) An image similar to a of an infected male embryo, in which a number of green pH2Av signals are detected. (e,f) Magnified images of boxed regions in d. Single-channelled images of e and f are shown in e′–e′′′ and f′–f′′′, respectively. In d–f, arrowheads indicate large pH2AX signals representing apoptotic nuclei, whereas arrows depict focal pH2AX signals representing DNA damage foci. (g) Quantification of focal pH2AX signals in uninfected and infected embryos at stage 11. Different letters (a,b) indicate statistically significant differences (P<0.05; Kruskal–Wallis test followed by Mann–Whitney U-tests). (h) Quantification of focal pH2AX signals overlapping with MSL1-labelled X chromosomes in uninfected and infected male embryos at stage 11. Asterisks indicate a statistically significant difference (**, P<0.01; Pearson's χ2 test). Focal pH2Av signals obtained in g were used to calculate the enrichment on the X chromosome in h. In g and h, box plots are as in Fig. 2i,j. Sample sizes (numbers of images analyzed) are shown at the bottom. Numbers of embryos inspected are shown in parentheses. Scale bars, 20 μm (a,d) and 5 μm (b–c′′′,e–f′′′).

Mentions: A previous study reported that maternal–zygotic Drosophila mutants for msl genes escape Spiroplasma-induced male-killing, suggesting that dosage compensation of the single male X chromosome is required for male-killing expression23. Hence, we hypothesized that the male X chromosome bound by the MSL complex may be the target of Spiroplasma-induced DNA damage, and tested the hypothesis by visualizing the male X chromosome and DNA-damage foci simultaneously using anti-MSL1 and anti-pH2Av antibodies in the embryonic epidermal cells where Spiroplasma-induced abnormal apoptosis predominantly occurs26. In infected male embryos, MSL1 signals and pH2Av signals were frequently overlapping, while such overlapped signals were infrequent in control embryos (Fig. 3a–f). Quantitative analysis of the co-localized MSL1 and pH2Av signals revealed that significantly more focal pH2Av signals were located on the X chromosome of infected male embryos in comparison with control embryos (Fig. 3g,h), indicating that DNA damage is specifically enriched on the X chromosome of infected male embryos. These results support the hypothesis that the male X chromosome is a major target of Spiroplasma-induced DNA damage, which plausibly underlies the p53-dependent apoptosis observed in infected male embryos.


Male-killing symbiont damages host's dosage-compensated sex chromosome to induce embryonic apoptosis
DNA damage in the X chromosome of Spiroplasma-infected male embryos.(a) Simultaneous detection of pH2Av (DNA damage foci or apoptotic nuclei; green), MSL1 (X chromosomes; magenta) and DNA (blue) in an uninfected male embryo at stage 11, wherein few green pH2Av signals are seen. (b,c) Magnified images of boxed regions in a. Single-channelled images of b and c are shown in b′–b′′′ and c′–c′′′, respectively. (d) An image similar to a of an infected male embryo, in which a number of green pH2Av signals are detected. (e,f) Magnified images of boxed regions in d. Single-channelled images of e and f are shown in e′–e′′′ and f′–f′′′, respectively. In d–f, arrowheads indicate large pH2AX signals representing apoptotic nuclei, whereas arrows depict focal pH2AX signals representing DNA damage foci. (g) Quantification of focal pH2AX signals in uninfected and infected embryos at stage 11. Different letters (a,b) indicate statistically significant differences (P<0.05; Kruskal–Wallis test followed by Mann–Whitney U-tests). (h) Quantification of focal pH2AX signals overlapping with MSL1-labelled X chromosomes in uninfected and infected male embryos at stage 11. Asterisks indicate a statistically significant difference (**, P<0.01; Pearson's χ2 test). Focal pH2Av signals obtained in g were used to calculate the enrichment on the X chromosome in h. In g and h, box plots are as in Fig. 2i,j. Sample sizes (numbers of images analyzed) are shown at the bottom. Numbers of embryos inspected are shown in parentheses. Scale bars, 20 μm (a,d) and 5 μm (b–c′′′,e–f′′′).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036004&req=5

f3: DNA damage in the X chromosome of Spiroplasma-infected male embryos.(a) Simultaneous detection of pH2Av (DNA damage foci or apoptotic nuclei; green), MSL1 (X chromosomes; magenta) and DNA (blue) in an uninfected male embryo at stage 11, wherein few green pH2Av signals are seen. (b,c) Magnified images of boxed regions in a. Single-channelled images of b and c are shown in b′–b′′′ and c′–c′′′, respectively. (d) An image similar to a of an infected male embryo, in which a number of green pH2Av signals are detected. (e,f) Magnified images of boxed regions in d. Single-channelled images of e and f are shown in e′–e′′′ and f′–f′′′, respectively. In d–f, arrowheads indicate large pH2AX signals representing apoptotic nuclei, whereas arrows depict focal pH2AX signals representing DNA damage foci. (g) Quantification of focal pH2AX signals in uninfected and infected embryos at stage 11. Different letters (a,b) indicate statistically significant differences (P<0.05; Kruskal–Wallis test followed by Mann–Whitney U-tests). (h) Quantification of focal pH2AX signals overlapping with MSL1-labelled X chromosomes in uninfected and infected male embryos at stage 11. Asterisks indicate a statistically significant difference (**, P<0.01; Pearson's χ2 test). Focal pH2Av signals obtained in g were used to calculate the enrichment on the X chromosome in h. In g and h, box plots are as in Fig. 2i,j. Sample sizes (numbers of images analyzed) are shown at the bottom. Numbers of embryos inspected are shown in parentheses. Scale bars, 20 μm (a,d) and 5 μm (b–c′′′,e–f′′′).
Mentions: A previous study reported that maternal–zygotic Drosophila mutants for msl genes escape Spiroplasma-induced male-killing, suggesting that dosage compensation of the single male X chromosome is required for male-killing expression23. Hence, we hypothesized that the male X chromosome bound by the MSL complex may be the target of Spiroplasma-induced DNA damage, and tested the hypothesis by visualizing the male X chromosome and DNA-damage foci simultaneously using anti-MSL1 and anti-pH2Av antibodies in the embryonic epidermal cells where Spiroplasma-induced abnormal apoptosis predominantly occurs26. In infected male embryos, MSL1 signals and pH2Av signals were frequently overlapping, while such overlapped signals were infrequent in control embryos (Fig. 3a–f). Quantitative analysis of the co-localized MSL1 and pH2Av signals revealed that significantly more focal pH2Av signals were located on the X chromosome of infected male embryos in comparison with control embryos (Fig. 3g,h), indicating that DNA damage is specifically enriched on the X chromosome of infected male embryos. These results support the hypothesis that the male X chromosome is a major target of Spiroplasma-induced DNA damage, which plausibly underlies the p53-dependent apoptosis observed in infected male embryos.

View Article: PubMed Central - PubMed

ABSTRACT

Some symbiotic bacteria are capable of interfering with host reproduction in selfish ways. How such bacteria can manipulate host's sex-related mechanisms is of fundamental interest encompassing cell, developmental and evolutionary biology. Here, we uncover the molecular and cellular mechanisms underlying Spiroplasma-induced embryonic male lethality in Drosophila melanogaster. Transcriptomic analysis reveals that many genes related to DNA damage and apoptosis are up-regulated specifically in infected male embryos. Detailed genetic and cytological analyses demonstrate that male-killing Spiroplasma causes DNA damage on the male X chromosome interacting with the male-specific lethal (MSL) complex. The damaged male X chromosome exhibits a chromatin bridge during mitosis, and bridge breakage triggers sex-specific abnormal apoptosis via p53-dependent pathways. Notably, the MSL complex is not only necessary but also sufficient for this cytotoxic process. These results highlight symbiont's sophisticated strategy to target host's sex chromosome and recruit host's molecular cascades toward massive apoptosis in a sex-specific manner.

No MeSH data available.