Related Experiment Videos
Ameiotic, a gene that controls meiotic chromosome and cytoskeletal behavior in maize
1Department of Molecular and Cellular Biology, University of California, Berkeley 94720.
Abstract:
Microtubule organization during the novel cell division of ameiotic microsporocytes was examined using indirect immunofluorescence microscopy. A recessive mutation of the maize gene Ameiotic causes the replacement of meiosis I with a synchronized mitotic division (Palmer, R. G. (1971). Chromosoma 35, 233-246). All identifiable cytological features of this division, including chromosome behavior and microtubule organization, were typical of somatic cell division. Significantly, a cortical microtubule band was observed during prophase in ameiotic cells. In most somatic plant cells, a preprophase band of microtubules (PPB) predicts the cortical site where the future cell plate will join the sidewall. Similar structures, however, are absent in all meiotic and postmeiotic reproductive cells examined to date. These disruptions are consistent with a model where the wild-type Ameiotic gene encodes a product which acts during or before G2 and is necessary for initiating several independent meiotic processes, including both meiotic chromosome behavior and microtubule organization. The ameiotic mutation provides additional evidence that aspects of cytoskeletal organization unique to meiosis are genetically controlled. Finally, the presence of a PPB during the ameiotic division supports a model whereby multiple mechanisms are used to determine and maintain division plane polarity during normal meiosis.
Insights
The ameiotic mutation in maize replaces meiosis I with mitosis, revealing a preprophase band of microtubules (PPB) typically absent in reproductive cells. This finding suggests genetic control over meiotic cytoskeletal organization.
Area of Science:
- Plant Cell Biology
- Genetics
- Cytoskeletal Dynamics
Background:
- Meiosis involves specialized cell divisions distinct from somatic mitosis.
- Reproductive cells typically lack structures like the preprophase band (PPB) seen in somatic cells.
- The maize Ameiotic gene is known to regulate meiotic progression.
Purpose of the Study:
- To investigate microtubule organization during the ameiotic mutation's novel cell division.
- To understand the role of the Ameiotic gene in cytoskeletal regulation during cell division.
- To compare microtubule organization in ameiotic cells with somatic and meiotic cells.
Main Methods:
- Indirect immunofluorescence microscopy was used to visualize microtubules.
- Cytological analysis of microsporocytes from ameiotic mutant maize.
- Comparison of microtubule organization with known patterns in somatic and meiotic cells.
Main Results:
- The ameiotic mutation results in a mitotic-like division instead of meiosis I.
- A preprophase band (PPB) of microtubules was observed in prophase ameiotic cells.
- This PPB is typically absent in meiotic and postmeiotic reproductive cells.
Conclusions:
- The Ameiotic gene product is likely required before or during G2 for initiating meiotic processes.
- Cytoskeletal organization unique to meiosis is under genetic control.
- The presence of a PPB in ameiotic division supports models of division plane determination in meiosis.