Abstract
Light microscope observations suggest there are two discrete biochemical domains in the plant kinetochore, an inner domain containing structural proteins, and an outer domain containing proteins involved in motility. We analyzed the ultrastructure of maize meiotic kinetochores following high pressure freezing and freeze substitution, a method that provides excellent sample preservation. Data from meiosis II support previous descriptions of plant kinetochores as diffuse, nearly invisible domains, sometimes nesting in a cup of darkly staining chromatin. The ultrastructure is similar in meiosis I but there are two sister kinetochores that each protrude away from the chromosome and form their own distinct kinetochore fibers. Microtubules terminate within kinetochores where their ends are splayed in a cone-shaped configuration suggestive of microtubule disassembly. We could not detect any significant substructure within the kinetochore proper. We suggest that the diffuse structure classically defined as the kinetochore represents only the outer domain of a two-domain organelle. The inner domain, known to contain chromatin-binding proteins, probably extends into the electron-dense chromatin of the primary constriction.
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Claims 6
Claim · model-written summary
Meiosis II kinetochores were diffuse and nearly invisible, sometimes in dark chromatin cups.
- Organ / stage
- meiosis IIe0
- Outcome
- diffuse, nearly invisible domainse0
- Qualifier
- sometimes nesting in a cup of darkly staining chromatine0
Not reportedTaxon
Verbatim
e0“Data from meiosis II support previous descriptions of plant kinetochores as diffuse, nearly invisible domains, sometimes nesting in a cup of darkly staining chromatin.”
Claim · model-written summary
In meiosis I, sister kinetochores protruded from chromosomes and formed distinct fibers.
Not reportedTaxon
Verbatim
e0“there are two sister kinetochores that each protrude away from the chromosome and form their own distinct kinetochore fibers.”
Claim · model-written summary
Microtubule ends terminated and splayed within kinetochores.
- Outcome
- Microtubules terminate within kinetochorese0
- Qualifier
- splayed in a cone-shaped configuratione0
Not reportedTaxon
Verbatim
e0“Microtubules terminate within kinetochores where their ends are splayed in a cone-shaped configuration suggestive of microtubule disassembly.”
Claim · model-written summary
No significant internal substructure was detected in the kinetochore proper.
- Outcome
- any significant substructure within the kinetochore propere0
Not reportedTaxon
Verbatim
e0“We could not detect any significant substructure within the kinetochore proper.”
Claim · model-written summary
The diffuse kinetochore likely represents the outer domain of a two domain organelle.
Not reportedTaxon
Verbatim
e0“the diffuse structure classically defined as the kinetochore represents only the outer domain of a two-domain organelle.”
Claim · model-written summary
The inner domain probably extends into chromatin of the primary constriction.
- Outcome
- extends into the electron-dense chromatin of the primary constrictione0
- Qualifier
- inner domaine0
Not reportedTaxon
Verbatim
e0“The inner domain, known to contain chromatin-binding proteins, probably extends into the electron-dense chromatin of the primary constriction.”