Abstract
Organization of kinetochore fiber microtubules (MTs) throughout mitosis in the endosperm of Haemanthus katherinae Bak. has been analysed using serial section reconstruction from electron micrographs. Accurate and complete studies have required careful analysis of individual MTs in precisely oriented serial sections through many (45) preselected cells. Kinetochore MTs (kMTs) and non-kinetochore MTs (nkMTs) intermingle within the fiber throughout division, undergoing characteristic, time-dependent, organizational changes. The number of kMTs increases progressively throughout the kinetochore during prometaphase-metaphase. Prometaphase chromosomes which were probably moving toward the pole at the time of fixation have unequally developed kinetochores associated with many nkMTs. The greatest numbers of kMTs (74-109/kinetochore), kinetochore cross-sectional area, and kMT central density all occur at metaphase. Throughout anaphase and telophase there is a decrease in the number of kMTs and, in the kinetochore cross-sectional area, an increased obliquity of kMTs and increased numbers of short MTs near the kinetochore. Delayed kinetochores possess more kMTs than do kinetochores near the poles, but fewer kMTs than chromosomes which have moved equivalent distances in other cells. The frequency of C-shaped proximal MT terminations within kinetochores is highest at early prometaphase and midtelophase, falling to zero at midanaphase. Therefore, in Haemanthus, MTs are probably lost from the periphery of the kinetochore during anaphase in a manner which is related to both time and position of the chromosome along the spindle axis. The complex, time-dependent organization of MTs in the kinetochore region strongly suggests that chromosome movement is accompanied by continual MT rearrangement and/or assembly/disassembly.
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Claims 13
Claim · model-written summary
Kinetochore and non-kinetochore microtubules intermingle within the fiber throughout division, undergoing characteristic time-dependent organizational changes.
Not reportedDirection
Verbatim
e0“Haemanthus katherinae Bak.”
e1“Kinetochore MTs (kMTs) and non-kinetochore MTs (nkMTs) intermingle within the fiber throughout division, undergoing characteristic, time-dependent, organizational changes”
Claim · model-written summary
The number of kinetochore microtubules increases progressively throughout the kinetochore during prometaphase-metaphase.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“The number of kMTs increases progressively throughout the kinetochore during prometaphase-metaphase”
Claim · model-written summary
Prometaphase chromosomes probably moving toward the pole at fixation have unequally developed kinetochores associated with many non-kinetochore microtubules.
- Taxon
- Haemanthus katherinaee0
- Organ / stage
- Prometaphasee1
- Outcome
- unequally developed kinetochores associated with many nkMTse1
Not reportedDirection
Verbatim
e0“Haemanthus katherinae Bak.”
e1“Prometaphase chromosomes which were probably moving toward the pole at the time of fixation have unequally developed kinetochores associated with many nkMTs”
Claim · model-written summary
The greatest number of kinetochore microtubules (74-109 per kinetochore) occurs at metaphase.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“The greatest numbers of kMTs (74-109/kinetochore), kinetochore cross-sectional area, and kMT central density all occur at metaphase”
Claim · model-written summary
Kinetochore cross-sectional area and kMT central density are greatest at metaphase.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“The greatest numbers of kMTs (74-109/kinetochore), kinetochore cross-sectional area, and kMT central density all occur at metaphase”
Claim · model-written summary
Throughout anaphase and telophase the number of kMTs and the kinetochore cross-sectional area decrease.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“Throughout anaphase and telophase there is a decrease in the number of kMTs and, in the kinetochore cross-sectional area”
Claim · model-written summary
Throughout anaphase and telophase there is an increased obliquity of kMTs and increased numbers of short MTs near the kinetochore.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“an increased obliquity of kMTs and increased numbers of short MTs near the kinetochore”
Claim · model-written summary
Delayed kinetochores possess more kMTs than kinetochores near the poles.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“Delayed kinetochores possess more kMTs than do kinetochores near the poles”
Claim · model-written summary
Delayed kinetochores possess fewer kMTs than chromosomes that have moved equivalent distances in other cells.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“Delayed kinetochores possess more kMTs than do kinetochores near the poles, but fewer kMTs than chromosomes which have moved equivalent distances in other cells”
Claim · model-written summary
The frequency of C-shaped proximal MT terminations within kinetochores is highest at early prometaphase and midtelophase.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“The frequency of C-shaped proximal MT terminations within kinetochores is highest at early prometaphase and midtelophase”
Claim · model-written summary
The frequency of C-shaped proximal MT terminations falls to zero at midanaphase.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“The frequency of C-shaped proximal MT terminations within kinetochores is highest at early prometaphase and midtelophase, falling to zero at midanaphase”
Claim · model-written summary
The authors conclude that in Haemanthus MTs are probably lost from the periphery of the kinetochore during anaphase in a manner related to both time and position of the chromosome along the spindle axis.
- Taxon
- Haemanthus
Haemanthuse1 - Organ / stage
- anaphasee1
- Outcome
- MTs are probably lost from the periphery of the kinetochoree1
- Qualifier
- related to both time and position of the chromosome along the spindle axise1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“in Haemanthus, MTs are probably lost from the periphery of the kinetochore during anaphase in a manner which is related to both time and position of the chromosome along the spindle axis”
Claim · model-written summary
The authors state that the time-dependent organization of MTs in the kinetochore region strongly suggests that chromosome movement is accompanied by continual MT rearrangement and/or assembly/disassembly.
Verbatim
e0“Haemanthus katherinae Bak.”
e1“strongly suggests that chromosome movement is accompanied by continual MT rearrangement and/or assembly/disassembly”