Special Behavior of Homo(eo)logous Chromosomes at Meiosis and the Mechanism of Partial Female Fertility of Allotriploid Lilium ‘triumphator’ (LLO)

Background: The abnormal meiosis of triploid is paid little attention; however, triploid not only is an important trend of ornamental breeding but also is regarded as a bridge of plant polyploidy speciation. In the present research, an allotriploid lily ‘Triumphator’ (LLO, 2n = 3x = 36 ) was investigated. Results: The results showed that the homoeologous chromosomes of two L-genomes formed bivalents and then disjoined and their half-bivalents moved to opposite poles at anaphase I; The chromosomes of O-genome formed univalents, among which, some attached to spindle fibers on two sides, their sister chromtids moved to the opposite poles slower than half-bivalents; some attached to spindle fibers on one side, they move to one pole at similar speed to half-bivalents; some of which deattached to spindle fibers at kinechores on either side, they became micronuclei at anaphase I. Conclusions: Interploid hybridizaitons showed that the LLO lily, regarless of male sterile, could be female parents to crossed with appropriate males to produce aneuploids, supporting the hypothesis -- five same genomes is essential for its endosperm development in interploid hybridizations of Lilium. The discussion well not only explained why triploid lilies with Fritillaria embryo sacs, regardless of male sterile, are usually partial female fertile while other plants with polygonum embryo sacs are seedless; but also explained that why 3x × 2x/4x lilies and tulips produce predominantly aneuploids while 3x × 2x/4x and 2x/4x × 3x of other plants, including 2x/4x × 3x of lilies and tulips, produce euploids and near so.

Meiotic irregularities in Capsicum L. species

Cytogenetic and pollen viability (PV) studies were performed in pepper accessions, Capsicum chinense and Capsicum baccatum. Irregularities such as laggard and univalent chromosomes, bridges, problems in the spindle fibers and cytomixis were observed, especially in C. baccatum which was the most unstable genotype. In the post-meiotic products, irregularities were observed, on average, at 20 % of the microspores in C. baccatum and 17 % in C. chinense. PV in C. baccatum was below 70 %, while in C. chinense, it was above 80 %. Meiotic irregularities in Capsicum, mainly in C. baccatum, considering the low PV estimated, were significant but not impeditive for fertilization.

Meiotic behavior of wild Caricaceae species potentially suitable for papaya improvement

The purpose of this study was to evaluate the meiotic behavior and determine the meiotic index and pollen viability of representative plants of the wild species V. goudotiana, V. quercifolia and J. spinosa. Meiotic analysis confirmed that the species are diploid and have 18 chromosomes. Meiosis was partially normal, since some abnormalities, e.g, sticky and lagging chromosomes, precocious segregation, lack of synchrony, and disturbances in the spindle fibers were observed. These abnormalities resulted in post-meiotic products (monads, dyads, triads, and polyads) that probably contributed to the meiotic index of 85.7 % (V. goudotiana) to 95.9 % (J. spinosa); significant variation was observed in the species V. goudotiana. The pollen viability of 68.0 % (V. goudotiana) to 96.0 % (J. spinosa) was reasonably good in these wild species. Crossings in breeding programs involving V. goudotiana should therefore be carefully planned, since part of the gametes of this species is unviable.

Requirements for NuMA in maintenance and establishment of mammalian spindle poles

Microtubules of the mitotic spindle in mammalian somatic cells are focused at spindle poles, a process thought to include direct capture by astral microtubules of kinetochores and/or noncentrosomally nucleated microtubule bundles. By construction and analysis of a conditional loss of mitotic function allele of the nuclear mitotic apparatus (NuMA) protein in mice and cultured primary cells, we demonstrate that NuMA is an essential mitotic component with distinct contributions to the establishment and maintenance of focused spindle poles. When mitotic NuMA function is disrupted, centrosomes provide initial focusing activity, but continued centrosome attachment to spindle fibers under tension is defective, and the maintenance of focused kinetochore fibers at spindle poles throughout mitosis is prevented. Without centrosomes and NuMA, initial establishment of spindle microtubule focusing completely fails. Thus, NuMA is a defining feature of the mammalian spindle pole and functions as an essential tether linking bulk microtubules of the spindle to centrosomes.

Cytogenetic effects of insecticide Lamda cyhalothrin on meristemic cells of Allium cepa L.

The effect of insecticide lamda cyhalothrin on Allium cepa L.root meristem were studied cytogenetically .Using three concentrations of the insecticide 5%, 7.5%, 10% at 6,12,24hours treatments . The insecticide significantly reduced the mitotic index at all concentrations. Moreover showed its ability to induced C – metaphase in 10% .The effects were also caused chromosome aberration like stickness in anaphase, telophase, binucleated cells, Micronuclei formation. These alternations indicating that this insecticide was effective in producing disturbance of spindle fibers.

A microtubule-destabilizing kinesin motor regulates spindle length and anchoring in oocytes

The kinesin-13 motor, KLP10A, destabilizes microtubules at their minus ends in mitosis and binds to polymerizing plus ends in interphase, regulating spindle and microtubule dynamics. Little is known about kinesin-13 motors in meiosis. In this study, we report that KLP10A localizes to the unusual pole bodies of anastral Drosophila melanogaster oocyte meiosis I spindles as well as spindle fibers, centromeres, and cortical microtubules. We frequently observe the pole bodies attached to cortical microtubules, indicating that KLP10A could mediate spindle anchoring to the cortex via cortical microtubules. Oocytes treated with drugs that suppress microtubule dynamics exhibit spindles that are reoriented more vertically to the cortex than untreated controls. A dominant-negative klp10A mutant shows both reoriented and shorter oocyte spindles, implying that, unexpectedly, KLP10A may stabilize rather than destabilize microtubules, regulating spindle length and positioning the oocyte spindle. By altering microtubule dynamics, KLP10A could promote spindle reorientation upon oocyte activation.