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Drosophila eggshell production: identification of new genes and coordination by Pxt.

Tootle TL, Williams D, Hubb A, Frederick R, Spradling A - PLoS ONE (2011)

Bottom Line: Mutations in pxt, encoding a putative Drosophila cyclooxygenase, cause many transcripts to begin expression prematurely, and are associated with eggshell defects.One of the temporally regulated genes, cyp18a1, which encodes a cytochromome P450 protein mediating ecdysone turnover, is downregulated in pxt mutant follicles, and cyp18a1 mutation itself alters eggshell gene expression.These studies further define the molecular program of Drosophila follicle maturation and support the idea that it is coordinated by lipid and steroid hormonal signals.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Roy J. and Lucille Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America. tina-tootle@uiowa.edu

ABSTRACT
Drosophila ovarian follicles complete development using a spatially and temporally controlled maturation process in which they resume meiosis and secrete a multi-layered, protective eggshell before undergoing arrest and/or ovulation. Microarray analysis revealed more than 150 genes that are expressed in a stage-specific manner during the last 24 hours of follicle development. These include all 30 previously known eggshell genes, as well as 19 new candidate chorion genes and 100 other genes likely to participate in maturation. Mutations in pxt, encoding a putative Drosophila cyclooxygenase, cause many transcripts to begin expression prematurely, and are associated with eggshell defects. Somatic activity of Pxt is required, as RNAi knockdown of pxt in the follicle cells recapitulates both the temporal expression and eggshell defects. One of the temporally regulated genes, cyp18a1, which encodes a cytochromome P450 protein mediating ecdysone turnover, is downregulated in pxt mutant follicles, and cyp18a1 mutation itself alters eggshell gene expression. These studies further define the molecular program of Drosophila follicle maturation and support the idea that it is coordinated by lipid and steroid hormonal signals.

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pxt mutants disrupt eggshell production.(A–C) Light microscopic images of laid, dechorionated eggs incubated with neutral red dye. Wild-type eggs (y w) are impermeable and exclude the dye (A), while pxt mutant eggs often appear abnormal, especially at the anterior end, and have permeability defects allowing dye uptake (B–C). (D–H) Nudel expression. In wild type (y w) main body follicle cells secrete Nudel around the oocyte during stages 8–10A (D–E) and centripetally migrating follicle cells secrete it at the anterior of the oocyte during stage 10B. In contrast, in pxt mutant follicles, Nudel is secreted prematurely, both at the anterior and away from the oocyte (F–G, arrows). (I–K) Light microscope images of laid eggs. The outer shell layers (chorion) are morphologically abnormal in laid pxt mutant eggs. Dorsal appendages are short, and misformed (J), and the main body chorion is uneven and rough (J–K), compared to wild-type laid eggs (I).
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pone-0019943-g004: pxt mutants disrupt eggshell production.(A–C) Light microscopic images of laid, dechorionated eggs incubated with neutral red dye. Wild-type eggs (y w) are impermeable and exclude the dye (A), while pxt mutant eggs often appear abnormal, especially at the anterior end, and have permeability defects allowing dye uptake (B–C). (D–H) Nudel expression. In wild type (y w) main body follicle cells secrete Nudel around the oocyte during stages 8–10A (D–E) and centripetally migrating follicle cells secrete it at the anterior of the oocyte during stage 10B. In contrast, in pxt mutant follicles, Nudel is secreted prematurely, both at the anterior and away from the oocyte (F–G, arrows). (I–K) Light microscope images of laid eggs. The outer shell layers (chorion) are morphologically abnormal in laid pxt mutant eggs. Dorsal appendages are short, and misformed (J), and the main body chorion is uneven and rough (J–K), compared to wild-type laid eggs (I).

Mentions: We examined the structure of pxt mutant eggs to determine if the expression changes observed above were associated with eggshell defects. To assess the vitelline membrane integrity, we examined whether dechorionated eggs are impermeable to neutral red dye. 41% (n = 179) of laid pxtf01000 eggs and 34% (n = 240) of laid pxtEY03052 eggs took up dye, indicating a vitelline membrane defect, compared to only 1.7% (n = 675) of yw eggs (Figure 4B–C, compared to A). While dye uptake was frequently localized near the anterior egg region, 25–30% of pxt mutant eggs took up dye along the entire anterior-posterior axis. Thus, examination of eggs laid by pxt mutants revealed defects in eggshell structure, supporting the idea that Pxt-mediated temporal gene regulation is necessary for proper eggshell formation.


Drosophila eggshell production: identification of new genes and coordination by Pxt.

Tootle TL, Williams D, Hubb A, Frederick R, Spradling A - PLoS ONE (2011)

pxt mutants disrupt eggshell production.(A–C) Light microscopic images of laid, dechorionated eggs incubated with neutral red dye. Wild-type eggs (y w) are impermeable and exclude the dye (A), while pxt mutant eggs often appear abnormal, especially at the anterior end, and have permeability defects allowing dye uptake (B–C). (D–H) Nudel expression. In wild type (y w) main body follicle cells secrete Nudel around the oocyte during stages 8–10A (D–E) and centripetally migrating follicle cells secrete it at the anterior of the oocyte during stage 10B. In contrast, in pxt mutant follicles, Nudel is secreted prematurely, both at the anterior and away from the oocyte (F–G, arrows). (I–K) Light microscope images of laid eggs. The outer shell layers (chorion) are morphologically abnormal in laid pxt mutant eggs. Dorsal appendages are short, and misformed (J), and the main body chorion is uneven and rough (J–K), compared to wild-type laid eggs (I).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3102670&req=5

pone-0019943-g004: pxt mutants disrupt eggshell production.(A–C) Light microscopic images of laid, dechorionated eggs incubated with neutral red dye. Wild-type eggs (y w) are impermeable and exclude the dye (A), while pxt mutant eggs often appear abnormal, especially at the anterior end, and have permeability defects allowing dye uptake (B–C). (D–H) Nudel expression. In wild type (y w) main body follicle cells secrete Nudel around the oocyte during stages 8–10A (D–E) and centripetally migrating follicle cells secrete it at the anterior of the oocyte during stage 10B. In contrast, in pxt mutant follicles, Nudel is secreted prematurely, both at the anterior and away from the oocyte (F–G, arrows). (I–K) Light microscope images of laid eggs. The outer shell layers (chorion) are morphologically abnormal in laid pxt mutant eggs. Dorsal appendages are short, and misformed (J), and the main body chorion is uneven and rough (J–K), compared to wild-type laid eggs (I).
Mentions: We examined the structure of pxt mutant eggs to determine if the expression changes observed above were associated with eggshell defects. To assess the vitelline membrane integrity, we examined whether dechorionated eggs are impermeable to neutral red dye. 41% (n = 179) of laid pxtf01000 eggs and 34% (n = 240) of laid pxtEY03052 eggs took up dye, indicating a vitelline membrane defect, compared to only 1.7% (n = 675) of yw eggs (Figure 4B–C, compared to A). While dye uptake was frequently localized near the anterior egg region, 25–30% of pxt mutant eggs took up dye along the entire anterior-posterior axis. Thus, examination of eggs laid by pxt mutants revealed defects in eggshell structure, supporting the idea that Pxt-mediated temporal gene regulation is necessary for proper eggshell formation.

Bottom Line: Mutations in pxt, encoding a putative Drosophila cyclooxygenase, cause many transcripts to begin expression prematurely, and are associated with eggshell defects.One of the temporally regulated genes, cyp18a1, which encodes a cytochromome P450 protein mediating ecdysone turnover, is downregulated in pxt mutant follicles, and cyp18a1 mutation itself alters eggshell gene expression.These studies further define the molecular program of Drosophila follicle maturation and support the idea that it is coordinated by lipid and steroid hormonal signals.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Roy J. and Lucille Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America. tina-tootle@uiowa.edu

ABSTRACT
Drosophila ovarian follicles complete development using a spatially and temporally controlled maturation process in which they resume meiosis and secrete a multi-layered, protective eggshell before undergoing arrest and/or ovulation. Microarray analysis revealed more than 150 genes that are expressed in a stage-specific manner during the last 24 hours of follicle development. These include all 30 previously known eggshell genes, as well as 19 new candidate chorion genes and 100 other genes likely to participate in maturation. Mutations in pxt, encoding a putative Drosophila cyclooxygenase, cause many transcripts to begin expression prematurely, and are associated with eggshell defects. Somatic activity of Pxt is required, as RNAi knockdown of pxt in the follicle cells recapitulates both the temporal expression and eggshell defects. One of the temporally regulated genes, cyp18a1, which encodes a cytochromome P450 protein mediating ecdysone turnover, is downregulated in pxt mutant follicles, and cyp18a1 mutation itself alters eggshell gene expression. These studies further define the molecular program of Drosophila follicle maturation and support the idea that it is coordinated by lipid and steroid hormonal signals.

Show MeSH