Abstract
The microtubular cytoskeleton of male-sterile Chinese cabbage was examined to characterize cytoplasmically based defects during microsporogenesis of fertile and sterile microsporocytes. At the onset of meiosis, microtubules (MTs) in fertile microsporocytes were short and anisotropically oriented in the microsporocyte cytoplasm. As the microsporocytes entered metaphase I, the MTs constructed a bisymmetrical spindle characterized by conspicuous kinetochore fibers closely associated with chromosomes in the medial plane. During anaphase I, interzonal MTs become conspicuous between the two sets of chromosomes and the polar regions become more distant as spindle MTs are depleted, essentially disappearing at telophase I. Radially distributed MTs increased and the microsporocyte entered meiosis II, producing two spindles at angles to one another within the wall of the microsporocyte. Indicative of the completion of anaphase II is the formation of a field of aligned MTs between two non-sister nuclei, after which the cytoplasm produced centripetal furrows, meeting in the center of the cell and dividing it into four microspores at the completion of cytokinesis. In sterile microsporocytes, however, an abnormal arrangement of MTs occurred at the conclusion of anaphase II. Although two spindles formed, the angle and the boundary between the spindles were not maintained. At the onset of telophase II, the two spindles migrated to a central region and laterally fused in irregular orientations in which the decondensing chromatin of the non-sister nuclei may form separate or merged nuclei, followed by irregular cytokinesis. The result of meiosis was 41.8 % two binuclear products, and 58.2 % one diploid and one binuclear sterile products.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.