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Spatial and developmental changes in the respiratory activity of mitochondria in early Drosophila embryos
Abstract:
Mitochondria of early Drosophila embryos were observed with a transmission electron microscope and a fluorescent microscope after vital staining with rhodamine 123, which accumulates only in active mitochondria. Rhodamine 123 accumulated particularly in the posterior pole region in early cleavage embryos, whereas the spatial distribution of mitochondria in an embryo was uniform throughout cleavage stages. In late cleavage stages, the dye showed very weak and uniform accumulation in all regions of periplasm. Polar plasm, sequestered in pole cells, restored the ability to accumulate the dye. Therefore, it is concluded that the respiratory activity of mitochondria is higher in the polar plasm than in the other regions of periplasm in early embryos, and this changes during development. The temporal changes in rhodamine 123-staining of polar plasm were not affected by u.v. irradiation at the posterior of early cleavage embryos at a sufficient dosage to prevent pole cell formation. This suggests that the inhibition of pole cell formation by u.v. irradiation is not due to the inactivation of the respiratory activities of mitochondria. In addition, we found that the anterior of Bicaudal-D mutant embryos at cleavage stage was stained with rhodamine 123 with the same intensity as the posterior of wild-type embryos. No pole cells form in the anterior of Bic-D embryos, where no restoration of mitochondrial activity occurs in the blastoderm stage. The posterior group mutations that we tested (staufen, oskar, tudor, nanos) and the terminal mutation (torso) did not alter staining pattern of the posterior with rhodamine 123.
Insights
Mitochondrial respiratory activity is higher in Drosophila embryo posterior pole plasm, visualized with rhodamine 123. This activity is crucial for pole cell formation and is unaffected by UV irradiation.
Area of Science:
- Developmental Biology
- Cell Biology
- Mitochondrial Research
Background:
- Mitochondria are vital for cellular energy production.
- Early Drosophila embryos possess specialized pole plasm crucial for development.
- Understanding mitochondrial activity in early development is key to developmental processes.
Purpose of the Study:
- To investigate the spatial and temporal distribution of mitochondrial respiratory activity in early Drosophila embryos.
- To determine the role of mitochondrial activity in pole cell formation.
- To assess the impact of UV irradiation and specific mutations on mitochondrial activity.
Main Methods:
- Vital staining of mitochondria using rhodamine 123 in early Drosophila embryos.
- Microscopic observation (transmission electron microscopy and fluorescence microscopy).
- Analysis of mitochondrial activity in wild-type, UV-irradiated, and mutant (Bicaudal-D, posterior group, torso) embryos.
Main Results:
- Rhodamine 123 accumulated intensely in the posterior pole plasm of early cleavage embryos, indicating high mitochondrial respiratory activity.
- Mitochondrial activity distribution became uniform later in cleavage stages.
- UV irradiation preventing pole cell formation did not affect rhodamine 123 staining patterns.
- Bicaudal-D mutant embryos showed uniform high mitochondrial activity anteriorly, similar to wild-type posterior, but without pole cell formation.
- Posterior group and torso mutations did not alter rhodamine 123 staining patterns.
Conclusions:
- Mitochondrial respiratory activity is significantly higher in the posterior pole plasm of early Drosophila embryos.
- This elevated mitochondrial activity is essential for pole cell formation.
- UV-induced inhibition of pole cell formation is independent of mitochondrial respiratory inactivation.
- Specific mutations affecting polarity do not necessarily abolish mitochondrial respiratory activity in the affected regions.