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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.


p53-dependent apoptosis in Spiroplasma-infected male embryos.(a) p53R-GFP expression (green) and TUNEL staining (magenta) in an infected female embryo at stage 12 (n=12). Single-channel images are shown in a′ and a′′. (b) An image similar to a of an infected male embryo (n=10), wherein high p53 activity and massive apoptosis are seen. Single-channel images are shown in b′ and b′′. (c,d) TUNEL staining of infected female and male wild-type embryos at stage 11. The yellow arrow denotes developmental apoptosis in the head region. (e,f) Images similar to c,d of infected female and male embryos mutant for p53. (g,h) TUNEL staining of infected female and male embryos mutant for p53 at stage 14. In c–h, the edges of embryonic epidermis are depicted by dashed yellow lines. (i) Quantification of TUNEL-positive areas in infected female and male embryos, wild type and mutant for p53 at stage 11–12. Different letters (a,b) indicate statistically significant differences (P<0.01; Kruskal–Wallis test followed by Mann–Whitney U-tests). (j) Quantification of TUNEL-positive areas in infected female and male embryos mutant for p53 at stage 14 onward. Asterisks indicate a statistically significant difference (**, P<0.01; Mann–Whitney U-test). In i and j, box plots indicate the median (bold line), the 25th and 75th percentiles (box edges), and the range (whiskers). Sample sizes are shown at the bottom. Scale bars, 100 μm.
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f2: p53-dependent apoptosis in Spiroplasma-infected male embryos.(a) p53R-GFP expression (green) and TUNEL staining (magenta) in an infected female embryo at stage 12 (n=12). Single-channel images are shown in a′ and a′′. (b) An image similar to a of an infected male embryo (n=10), wherein high p53 activity and massive apoptosis are seen. Single-channel images are shown in b′ and b′′. (c,d) TUNEL staining of infected female and male wild-type embryos at stage 11. The yellow arrow denotes developmental apoptosis in the head region. (e,f) Images similar to c,d of infected female and male embryos mutant for p53. (g,h) TUNEL staining of infected female and male embryos mutant for p53 at stage 14. In c–h, the edges of embryonic epidermis are depicted by dashed yellow lines. (i) Quantification of TUNEL-positive areas in infected female and male embryos, wild type and mutant for p53 at stage 11–12. Different letters (a,b) indicate statistically significant differences (P<0.01; Kruskal–Wallis test followed by Mann–Whitney U-tests). (j) Quantification of TUNEL-positive areas in infected female and male embryos mutant for p53 at stage 14 onward. Asterisks indicate a statistically significant difference (**, P<0.01; Mann–Whitney U-test). In i and j, box plots indicate the median (bold line), the 25th and 75th percentiles (box edges), and the range (whiskers). Sample sizes are shown at the bottom. Scale bars, 100 μm.

Mentions: DNA damage is caused by a variety of genotoxic stresses including ionizing radiation, UV, chemicals, reactive oxygen species and replication stresses like stalling or delaying of replication fork progression. In response to DNA damage, a well-known tumour suppressor gene p53 is activated, which triggers an assemblage of p53-dependent pathways to control cell cycle, DNA repair and apoptosis36. Our analysis using a fly strain with p53-responsive GFP reporter (p53R-GFP) revealed that p53 was strongly activated in infected male embryos (Fig. 2a,b). The Drosophila genome encodes a single p53 family member, which is required for DNA damage-induced apoptosis373839. Using a allele of p53, we demonstrated that abnormal apoptosis in infected male embryos was significantly suppressed at stage 11–12 (Fig. 2c–f,i). On the other hand, developmental apoptosis prominent around the head region at these stages2640 was not affected (Fig. 2c,e,f, arrows). Upon severe DNA damage such as double-strand breaks caused by ionizing radiation, apoptosis is induced in a time-delayed manner even when p53 is absent4142. Concordantly, p53-independent apoptosis was observed in infected male embryos from stage 14 onward (Fig. 2g,h,j). Taken together, these results strongly suggest that cells of Spiroplasma-infected male embryos suffer DNA damage, and then abnormal apoptosis is triggered via p53-dependent pathways.


Male-killing symbiont damages host's dosage-compensated sex chromosome to induce embryonic apoptosis
p53-dependent apoptosis in Spiroplasma-infected male embryos.(a) p53R-GFP expression (green) and TUNEL staining (magenta) in an infected female embryo at stage 12 (n=12). Single-channel images are shown in a′ and a′′. (b) An image similar to a of an infected male embryo (n=10), wherein high p53 activity and massive apoptosis are seen. Single-channel images are shown in b′ and b′′. (c,d) TUNEL staining of infected female and male wild-type embryos at stage 11. The yellow arrow denotes developmental apoptosis in the head region. (e,f) Images similar to c,d of infected female and male embryos mutant for p53. (g,h) TUNEL staining of infected female and male embryos mutant for p53 at stage 14. In c–h, the edges of embryonic epidermis are depicted by dashed yellow lines. (i) Quantification of TUNEL-positive areas in infected female and male embryos, wild type and mutant for p53 at stage 11–12. Different letters (a,b) indicate statistically significant differences (P<0.01; Kruskal–Wallis test followed by Mann–Whitney U-tests). (j) Quantification of TUNEL-positive areas in infected female and male embryos mutant for p53 at stage 14 onward. Asterisks indicate a statistically significant difference (**, P<0.01; Mann–Whitney U-test). In i and j, box plots indicate the median (bold line), the 25th and 75th percentiles (box edges), and the range (whiskers). Sample sizes are shown at the bottom. Scale bars, 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f2: p53-dependent apoptosis in Spiroplasma-infected male embryos.(a) p53R-GFP expression (green) and TUNEL staining (magenta) in an infected female embryo at stage 12 (n=12). Single-channel images are shown in a′ and a′′. (b) An image similar to a of an infected male embryo (n=10), wherein high p53 activity and massive apoptosis are seen. Single-channel images are shown in b′ and b′′. (c,d) TUNEL staining of infected female and male wild-type embryos at stage 11. The yellow arrow denotes developmental apoptosis in the head region. (e,f) Images similar to c,d of infected female and male embryos mutant for p53. (g,h) TUNEL staining of infected female and male embryos mutant for p53 at stage 14. In c–h, the edges of embryonic epidermis are depicted by dashed yellow lines. (i) Quantification of TUNEL-positive areas in infected female and male embryos, wild type and mutant for p53 at stage 11–12. Different letters (a,b) indicate statistically significant differences (P<0.01; Kruskal–Wallis test followed by Mann–Whitney U-tests). (j) Quantification of TUNEL-positive areas in infected female and male embryos mutant for p53 at stage 14 onward. Asterisks indicate a statistically significant difference (**, P<0.01; Mann–Whitney U-test). In i and j, box plots indicate the median (bold line), the 25th and 75th percentiles (box edges), and the range (whiskers). Sample sizes are shown at the bottom. Scale bars, 100 μm.
Mentions: DNA damage is caused by a variety of genotoxic stresses including ionizing radiation, UV, chemicals, reactive oxygen species and replication stresses like stalling or delaying of replication fork progression. In response to DNA damage, a well-known tumour suppressor gene p53 is activated, which triggers an assemblage of p53-dependent pathways to control cell cycle, DNA repair and apoptosis36. Our analysis using a fly strain with p53-responsive GFP reporter (p53R-GFP) revealed that p53 was strongly activated in infected male embryos (Fig. 2a,b). The Drosophila genome encodes a single p53 family member, which is required for DNA damage-induced apoptosis373839. Using a allele of p53, we demonstrated that abnormal apoptosis in infected male embryos was significantly suppressed at stage 11–12 (Fig. 2c–f,i). On the other hand, developmental apoptosis prominent around the head region at these stages2640 was not affected (Fig. 2c,e,f, arrows). Upon severe DNA damage such as double-strand breaks caused by ionizing radiation, apoptosis is induced in a time-delayed manner even when p53 is absent4142. Concordantly, p53-independent apoptosis was observed in infected male embryos from stage 14 onward (Fig. 2g,h,j). Taken together, these results strongly suggest that cells of Spiroplasma-infected male embryos suffer DNA damage, and then abnormal apoptosis is triggered via p53-dependent pathways.

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.