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Detection of the membrane-calcium distribution during mitosis in Haemanthus endosperm with chlorotetracycline
Insights
Calcium distribution during cell division was mapped using chlorotetracycline (CTC). Findings suggest a membrane system releases calcium to regulate cell division mechanics.
Area of Science:
- Cell Biology
- Biophysics
Background:
- Calcium ions (Ca++) play critical roles in cellular processes.
- Understanding calcium dynamics during mitosis is essential for cell division research.
Purpose of the Study:
- To investigate the distribution of membrane-associated calcium during mitosis in Haemanthus endosperm cells.
- To explore the role of calcium in regulating the mechanochemical events of mitosis.
Main Methods:
- Utilized the fluorescent chelate probe chlorotetracycline (CTC) to visualize calcium distribution.
- Observed CTC fluorescence patterns at various mitotic stages.
- Examined the effects of calcium perturbation using lanthanum, procaine, and EGTA.
Main Results:
- CTC fluorescence revealed distinct punctate (mitochondrial/plastid) and diffuse (endoplasmic reticulum) components.
- Diffuse fluorescence localized to chromosome-to-pole regions during metaphase and anaphase spindles.
- Calcium perturbation agents reduced diffuse fluorescence, supporting its role in mitosis.
Conclusions:
- A membrane system in the mitotic apparatus likely regulates localized calcium release.
- This calcium release is hypothesized to control the mechanochemical processes of cell division.
Abstract:
The distribution of membrane-associated calcium has been determined at various stages of mitosis in Haemanthus endosperm cells with the fluorescent chelate probe chlorotetracycline (CTC). CTC fluorescence in Haemanthus has two components: punctate, because of mitochondrial and plastid membrane-Ca++; and diffuse, primarily because of Ca++ associated with endoplasmic reticulum membranes. Punctate fluorescence assumes a polar distribution throughout mitosis. Cones of diffuse fluorescence in the chromosomse-to-pole regions of the metaphase spindle appear to coincide with the kinetochore fibers; during anaphase, the cones of fluorescence coalesce and this region of the spindle exhibits uniform diffuse fluorescence. Perturbation of the cellular Ca++ distribution by treatment with lanthanum, procaine, or EGTA results in a loss of diffuse fluorescence with no accompanying change in the intensity of punctate fluorescence. Detergent extraction of cellular membranes causes a total elimination of CTC fluorescence. CTC fluorescence of freshly teased crayfish claw muscle sarcoplasmic reticulum coincides with the A bands and is reduced by perfusion with lanthanum, procaine, and EGTA in a manner similar to that for diffuse fluorescence in the endosperm cells. These results are consistent with the hypothesis that a membrane system in the chromosome-to-pole region of the mitotic apparatus functions in the localized release of sequestered Ca++, thereby regulating the mechanochemical events of mitosis.