Equatorial Plate Research Articles

Cytogenics, morphology and viability of Borreria spinosa (Rubiaceae) pollen grains

Introduction: Borreria spinosa is a herbaceous plant considered a weed in agricultural crops, although it also has potential in apiculture. Despite its agronomic importance, its cytogenetic and palynological traits are poorly known. Objective: To do the cytogenetic characterization of B. spinosa, describe the morphology of its pollen grains, and estimate their potential viability. Methods: We collected plant material in Santiago del Estero, Argentina, in May 2017 and used classical methods (8-hydroxyquinoline and Farmer for mitosis and meiosis; viability with Müntzing; pollen morphology with nonacetolysed and acetolysed techniques, and SEM). Results: B. spinosa has a chromosome number of 2n = 56, with a karyotype of 46 m + 10 sm. Meiotic abnormalities mainly include chromosomes outside the equatorial plate, lagging chromosomes, and cytomixis. Pollen grains are small to medium-sized, suboblate to oblate-spheroidal, with a viability of 70%. This is a tetraploid species, most chromosomes are metacentric or submetacentric; and it has irregular meiotic behavior and cytomixis, with concomitant low viability in pollen grains. Conclusion: In B. spinose, pollen grains have similar characteristics to other species of the genus Borreria.

Cytogenetic analysis of meiotic behaviour and stability in a trigeneric hybrid (triticale x trigopiro).

Trigeneric hybrids in Triticeae may help to establish evolutionary relationships among different genomes present in the same cellular genetic background and to transfer different alien characters into cultivated wheat. In the present study, a trigeneric hybrid involving species of Triticum, Secale, and Thinopyrum was synthesized by crossing hexaploid triticale with hexaploid trigopiro. The meiotic behaviour of chromosomes belonging to different genomes was analyzed, using routine and in situ hybridization techniques in F1, F2, and F3 generations of the trigeneric hybrid. The purpose of this study was to determine the chromosome number and genomic constitution and to discuss the mechanisms involved in the stabilization of the artificial tricepiro hybrids. The chromosome number of the trigeneric F1 hybrid was 2n = 42. Between 12 and 16 bivalents were observed in the central zone of the equatorial meiotic plate and between 9 and 18 univalents were found in the periphery of the MI equatorial plate. Seven of these univalents showed hybridization signals with rye DNA. Lagging rye and non-rye chromosomes and separation of sister chromatids were found in anaphase I. Tetrads with a maximum of six micronuclei, with and without hybridization signals of rye DNA, were observed. After three generations, meiotic cells revealed the presence of 42 chromosomes and 21 bivalents in diakinesis cells. The presence of 14 rye (Secale cereale) chromosomes and the complete pairing of chromosomes in F3 hybrids suggest that rye chromosomes would be preferentially transmitted to the progeny and that an elimination mechanism would act on chromosomes of Thinopyrum and wheat D genome.

Evaluation of Genotoxic Effect of Phloxine by Allium Test

Phloxine is used as a food dye. In this study, genotoxicity of phloxine at the root tip of Allium cepa L. was investigated. A. cepa L. meristematic root tip cells were treated with ten different doses of phloxine. In this way, the EC50 value was determined. Then, phloxine was applied to root tips at EC50/2, EC50 and EC50×2 doses. Treatment time was determined as 24, 48 and 72 hours. As a result, it was revealed that phloxine caused chromosomal aberrations in cells in mitotic cycle at the root tip of A. cepa. There are equatorial plate shifting in metaphase, laggard chromosome, disturbed spindle, chromosome stickiness, C-mitosis, polar shifting among the observed chromosomal aberrations. It was stated that the % chromosomal aberration index (CAI) increased depending on concentration increase. It has been demonstrated that the highest % chromosomal aberration index occurred at the EC50×2 dose for 72 hours. According to the research, it was revealed that phloxine has a genotoxic effect on the root cells of A. cepa. For this reason, it can be emphasized that care should be taken in its use in foods.

Localization of 5S rDNA analysis of homologous pairing in tetraploid hybrids of red crucian carp (♀) × common carp (♂)

AbstractInterspecies crossing and allopolyploidization increase the opportunity for generating new breeding resources for fish farming. Allotetraploid hybrid fish (4nAT) were created by crossing red crucian carp (RCC, Carassius auratus red var., ♀) with common carp (CC, Cyprinus carpio L., ♂). However, the genetic pattern of the heterogeneous genomes during gametogenesis in 4nAT is still unclear, which hinders the understanding of the mechanism of generation of new phenotypes during allopolyploidization in fish breeding. In the present study, fluorescence in situ hybridization of 5S rDNA was employed to track homologous pairing, and the characteristics of bivalents were observed using air‐drying preparation technology and electron microscopy. The results showed two strong signals of 5S rDNA localization from the RCC genome, paired in the pachytene stage and metaphase stage of meiosis I cells in 4nAT, suggesting pairing of homologous chromosomes in 4nAT occurred between identical chromosomes. Furthermore, all bivalent pairs possessed one monochiasmate and were neatly arranged in the equatorial plate during meiosis I, which ensured normal separation of homologous chromosomes in 4nAT. This study elucidated the genetic pattern of heterogeneous genomes in 4nAT, providing important evidence for the genetic stability of 4nAT. These findings are of great significance for aquatic breeding.

Obtain inter-section hybrids between Primula forbesii (Sect. Monocarpicae) and P. saxatilis (Sect. Cortusoides)

To breed excellent cultivars with prosperous fragrant flowers, long flowering period, and high resistance to hardiness, three Primula forbesii (Sect. Monocarpicae) cultivars (2n=2x=18) and P. saxatilis (Sect. Cortusoides) (2n=2x=24) were used as parents for hybridization. Fourteen progenies were obtained from three cross combinations of P. forbesii as maternal parent by embryo rescue. Eventually, 12 progenies were proved to be true hybrids (2n=2x=21) by flow cytometry, chromosome counting and amplified fragment length polymorphism analysis. All the hybrids had long lasting flowering period just like P. forbesii, and their leaf back and scapes were not covered by white powder like P. saxatilis. The hybrid progenies were more similar to their male parent P. saxatilis by phenotypes analysis. Pollen of hybrids was abnormal and the germination rates were very low (3.18%–0.23%). Phenomena such as chromosome outside the equatorial plate, lagging chromosomes, chromosome bridges, micronucleus and polyads happened during the process of pollen mother cell meiosis, resulting pollen abortion finally. The results of backcrossing with their parents as pollen donators indicated that the pollen was able to germinate on the stigma surface and pollen tubes could extend into the hybrids’ ovules. It was showed that the inter-section hybrids could be used as female parent, but could not be used as pollen donator in continuing hybridization.

Effect of Ferrous Gluconate on Chromosomal Abnormality Index of Allium Cepa Root Tip

In completed research, ferrous gluconate -a food additive- used to preserve black color to prevent discoloration during storage in ripe black olives, and Allium cepa L. species. A. cepa L. roots were treated with different doses of ferrous gluconate. The effective concentration EC50 (0.068 g/l) was determined. A. cepa root tips were treated with EC50/2 (0.034 g/l), EC50 (0.068 g/l), 2XEC50 (0.136 g/l) dose for 24, 48, 72 hours, and afterward, the root tips were prepared for observation under the light microscope according to the method of preparing mitotic preparation. Chromosomal abnormality index (CAI) and genotoxic effect of ferrous gluconate in A. cepa root tip cells were determined. Repeated measurement ANOVA and TUKEY multiple comparison tests were used to investigate the effect of time and dose together on genotoxicity. C-mitosis, polyploidy, polar shifting in anaphase, polar shifting in telophase, equatorial plate shifting, laggard chromosome was observed by microscope. The highest CAI (70.16±4.85) was observed at 72h for 2XEC50 dose. Chromosomal aberration is also observed in control group. While the most common chromosomal aberration is determined as C-mitosis; The least observed chromosomal aberration is determined as polyploidy. Research results revealed that ferrous gluconate has a genotoxic effect on the root tip of A. cepa.

Haploid Bio-Induction in Plant through Mock Sexual Reproduction.

SummaryHaploidization is invaluable for basic genetic research and crop breeding. The haploid bio-induction principle is an important topic that remains largely unexplored. In this study, both CenH3 RNAi and in vitro inhibition were used to simulate and induce haploids in allopolyploid crop. Notably, in vitro CenH3 inhibition showed that the results were much the same to that of RNAi in phenotype, chromosome behavior, microspore production, and haploid induction. Cytological analyses of RNAi and inhibitor-treated progenies revealed elimination of chromosomes, defective microspores with empty nuclei, thereby giving rise to pseudo male gametes, and haploid parthenogenesis induction. We found distinct defective empty microspores that were positively correlated with the decrease of CenH3 during RNAi manipulation. Investigation through both in vivo and in vitro studies revealed that haploidization was induced through the pseudo male gamete-mediated mock sexual reproduction. The present results provide insights for the haploid parthenogenesis induction process.

Kinesin-7 CENP-E regulates chromosome alignment and genome stability of spermatogenic cells

Kinesin-7 CENP-E is an essential kinetochore motor required for chromosome alignment and congression. However, the specific functions of CENP-E in the spermatogenic cells during spermatogenesis remain unknown. In this study, we find that CENP-E proteins are expressed in the spermatogonia, spermatocytes, and the elongating spermatids. CENP-E inhibition by specific inhibitor GSK923295 results in the disruption of spermatogenesis and cell cycle arrest of spermatogenic cells. Both spermatogonia and spermatocytes are arrested in metaphase and several chromosomes are not aligned at the equatorial plate. We find that CENP-E inhibition leads to chromosome misalignment, the spindle disorganization, and the formation of the aneuploidy cells. Furthermore, the inhibition of CENP-E results in the defects in the formation of spermatids, including the sperm head condensation and the sperm tail formation. We have revealed that kinesin-7 CENP-E is essential for chromosome alignment and genome stability of the spermatogenic cells.

Characterization and Evaluation of Resistance to Powdery Mildew of Wheat-Aegilops geniculata Roth 7Mg (7A) Alien Disomic Substitution Line W16998.

Aegilops geniculata Roth has been used as a donor of disease-resistance genes, to enrich the gene pool for wheat (Triticum aestivum) improvement through distant hybridization. In this study, the wheat–Ae. geniculata alien disomic substitution line W16998 was obtained from the BC1F8 progeny of a cross between the common wheat ‘Chinese Spring’ (CS) and Ae. geniculata Roth (serial number: SY159//CS). This line was identified using cytogenetic techniques, analysis of genomic in situ hybridization (GISH), functional molecular markers (Expressed sequence tag-sequence-tagged site (EST–STS) and PCR-based landmark unique gene (PLUG), fluorescence in situ hybridization (FISH), sequential fluorescence in situ hybridization–genomic in situ hybridization (sequential FISH–GISH), and assessment of agronomic traits and powdery mildew resistance. During the anaphase of meiosis, these were evenly distributed on both sides of the equatorial plate, and they exhibited high cytological stability during the meiotic metaphase and anaphase. GISH analysis indicated that W16998 contained a pair of Ae. geniculata alien chromosomes and 40 common wheat chromosomes. One EST–STS marker and seven PLUG marker results showed that the introduced chromosomes of Ae. geniculata belonged to homoeologous group 7. Nullisomic–tetrasomic analyses suggested that the common wheat chromosome, 7A, was absent in W16998. FISH and sequential FISH–GISH analyses confirmed that the introduced Ae. geniculata chromosome was 7Mg. Therefore, W16998 was a wheat–Ae. geniculata 7Mg (7A) alien disomic substitution line. Inoculation of isolate E09 (Blumeria graminis f. sp. tritici) in the seedling stage showed that SY159 and W16998 were resistant to powdery mildew, indeed nearly immune, whereas CS was highly susceptible. Compared to CS, W16998 exhibited increased grain weight and more spikelets, and a greater number of superior agronomic traits. Consequently, W16998 was potentially useful. Germplasms transfer new disease-resistance genes and prominent agronomic traits into common wheat, giving the latter some fine properties for breeding.

The CRL4-DCAF13 ubiquitin E3 ligase supports oocyte meiotic resumption by targeting PTEN degradation.

Cullin ring-finger ubiquitin ligase 4 (CRL4) has multiple functions in the maintenance of oocyte survival and meiotic cell cycle progression. DCAF13, a novel CRL4 adaptor, is essential for oocyte development. But the mechanisms by which CRL4-DCAF13 supports meiotic maturation remained unclear. In this study, we demonstrated that DCAF13 stimulates the meiotic resumption-coupled activation of protein synthesis in oocytes, partially by maintaining the activity of PI3K signaling pathway. CRL4-DCAF13 targets the polyubiquitination and degradation of PTEN, a lipid phosphatase that inhibits PI3K pathway as well as oocyte growth and maturation. Dcaf13 knockout in oocytes caused decreased CDK1 activity and impaired meiotic cell cycle progression and chromosome condensation defects. As a result, chromosomes fail to be aligned at the spindle equatorial plate, the spindle assembly checkpoint is activated, and most Dcaf13 null oocytes are arrested at the prometaphase I. The DCAF13-dependent PTEN degradation mechanism fits in as a missing link between CRL4 ubiquitin E3 ligase and PI3K pathway, both of which are crucial for translational activation during oocyte GV-MII transition.

Mitotic Catastrophe Induced in HeLa Tumor Cells by Photodynamic Therapy with Methyl-aminolevulinate.

Photodynamic therapy (PDT) constitutes a cancer treatment modality based on the administration of a photosensitizer, which accumulates in tumor cells. The subsequent irradiation of the tumoral area triggers the formation of reactive oxygen species responsible for cancer cell death. One of the compounds approved in clinical practice is methyl-aminolevulinate (MAL), a protoporphyrin IX (PpIX) precursor intermediate of heme synthesis. We have identified the mitotic catastrophe (MC) process after MAL-PDT in HeLa human carcinoma cells. The fluorescence microscopy revealed that PpIX was located mainly at plasma membrane and lysosomes of HeLa cells, although some fluorescence was also detected at endoplasmic reticulum and Golgi apparatus. Cell blockage at metaphase-anaphase transition was observed 24 h after PDT by phase contrast microscopy and flow cytometry. Mitotic apparatus components evaluation by immunofluorescence and Western blot indicated: multipolar spindles and disorganized chromosomes in the equatorial plate accompanied with dispersion of centromeres and alterations in aurora kinase proteins. The mitotic blockage induced by MAL-PDT resembled that induced by two compounds used in chemotherapy, taxol and nocodazole, both targeting microtubules. The alterations in tumoral cells provided evidence of MC induced by MAL-PDT, resolving mainly by apoptosis, directly or through the formation of multinucleate cells.

Distribution of plastids and mitochondria during male gametophyte formation in Tinantia erecta (Jacq.) Fenzl

During meiosis in microsporogenesis, autonomous cellular organelles, i.e., plastids and mitochondria, move and separate into daughter cells according to a specific pattern. This process called chondriokinesis is characteristic for a given plant species. The key criterion for classification of the chondriokinesis types was the arrangement of cell organelles during two meiosis phases: metaphase I and telophase I. The autonomous organelles participate in cytoplasmic inheritance; therefore, their precise distribution to daughter cells determines formation of identical viable microspores. In this study, the course of chondriokinesis during the development of the male gametophyte in Tinantia erecta was analyzed. The study was conducted using optical and transmission electron microscopes. During microsporogenesis in T. erecta, autonomous cell organelles moved in a manner defined as a neutral-equatorial type of chondriokinesis. Therefore, metaphase I plastids and mitochondria were evenly dispersed around the metaphase plate and formed an equatorial plate between the daughter nuclei in early telophase I. Changes in the ultrastructure of plastids and mitochondria during pollen microsporogenesis were also observed.

Mechanisms of kinesin-7 CENP-E in kinetochore-microtubule capture and chromosome alignment during cell division.

Chromosome congression is essential for faithful chromosome segregation and genomic stability in cell division. Centromere-associated protein E (CENP-E), a plus-end-directed kinesin motor, is required for congression of pole-proximal chromosomes in metaphase. CENP-E accumulates at the outer plate of kinetochores and mediates the kinetochore-microtubule capture. CENP-E also transports the chromosomes along spindle microtubules towards the equatorial plate. CENP-E interacts with Bub1-related kinase, Aurora B and core kinetochore components during kinetochore-microtubule attachment. In this review, we introduce the structures and mechanochemistry of kinesin-7 CENP-E. We highlight the complicated interactions between CENP-E and partner proteins during chromosome congression. We summarise the detailed roles and mechanisms of CENP-E in mitosis and meiosis, including the kinetochore-microtubule capture, chromosome congression/alignment in metaphase and the regulation of spindle assembly checkpoint. We also shed a light on the roles of CENP-E in tumourigenesis and CENP-E's specific inhibitors.

Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean

Large-magnitude intraplate earthquakes within the ocean basins are not well understood. The Mw 8.6 and Mw 8.2 strike-slip intraplate earthquakes on 11 April 2012, while clearly occurring in the equatorial Indian Ocean diffuse plate boundary zone, are a case in point, with disagreement on the nature of the focal mechanisms and the faults that ruptured. We use bathymetric and seismic reflection data from the rupture area of the earthquakes in the northern Wharton Basin to demonstrate pervasive brittle deformation between the Ninetyeast Ridge and the Sunda subduction zone. In addition to evidence of recent strike-slip deformation along approximately north-south–trending fossil fracture zones, we identify a new type of deformation structure in the Indian Ocean: conjugate Riedel shears limited to the sediment section and oriented oblique to the north-south fracture zones. The Riedel shears developed in the Miocene, at a similar time to the onset of diffuse deformation in the central Indian Ocean. However, left-lateral strike-slip reactivation of existing fracture zones started earlier, in the Paleocene to early Eocene, and compartmentalizes the Wharton Basin. Modeled rupture during the 11 April 2012 intraplate earthquakes is consistent with the location of two reactivated, closely spaced, approximately north-south–trending fracture zones. However, we find no evidence for WNW-ESE–trending faults in the shallow crust, which is at variance with most of the earthquake fault models.

Chromosome stickiness impairs meiosis and influences reproductive success in Panicum maximum (Poaceae) hybrid plants.

Chromosome stickiness has been studied in several species of higher plants and is characterized by sticky clumps of chromatin resulting in sterility. Chromosome stickiness was recorded in Panicum maximum hybrid plants that were cultivated in the field. In the meiocytes affected, chromosomes clumped into amorphous masses that did not orient themselves on the equatorial plate, and anaphase I disjunction failed to occur. After a normal cytokinesis, the masses of chromatin were divided between both daughter cells. Metaphase and anaphase of the second division also did not occur, and after the second cytokinesis, polyads were formed. This abnormality arose spontaneously. Abnormalities that cause male sterility are an important tool for obtaining hybrid seeds in plant breeding. This is the first report of an abnormality affecting pollen viability in P. maximum. This finding can open a new opportunity in the breeding program of this species that is devoted to hybridization where manual cross-pollination is difficult and time consuming.

Formation and structures of GroEL:GroES 2 chaperonin footballs, the protein-folding functional form

The GroE chaperonins assist substrate protein (SP) folding by cycling through several conformational states. With each cycle the SP is, in turn, captured, unfolded, briefly encapsulated (t1/2 ∼ 1 s), and released by the chaperonin complex. The protein-folding functional form is the US-football-shaped GroEL:GroES2 complex. We report structures of two such "football" complexes to ∼ 3.7-Å resolution; one is empty whereas the other contains encapsulated SP in both chambers. Although encapsulated SP is not visible on the electron density map, using calibrated FRET and order-of-addition experiments we show that owing to SP-catalyzed ADP/ATP exchange both chambers of the football complex encapsulate SP efficiently only if the binding of SP precedes that of ATP. The two rings of GroEL thus behave as a parallel processing machine, rather than functioning alternately. Compared with the bullet-shaped GroEL:GroES1 complex, the GroEL:GroES2 football complex differs conformationally at the GroEL-GroES interface and also at the interface between the two GroEL rings. We propose that the electrostatic interactions between the ε-NH(3+) of K105 of helix D in one ring with the negatively charged carboxyl oxygen of A109 at the carboxyl end of helix D of the other ring provide the structural basis for negative inter-ring cooperativity.

Amphitelic orientation of centromeres at metaphase I is an important feature for univalent-dependent meiotic nonreduction.

Univalent-dependent meiotic nonreduction, which leads to the production of unreduced gametes, is thought to be the predominant mechanism underlying allopolyploid plant formation. However, little is known about the underlying cytological mechanism. In the present study, we observed male sporogenesis in F1 amphihaploid hybrids of wheat–rye by FISH with the help of diagnostic PrCEN-1 specific for the rye centromere. Our observations indicated that at meiotic metaphase I, the chromosomes were accumulated on the equatorial plate. At this stage, the elongated centromeres were amphitelically oriented perpendicular to the equatorial plate, indicating tension from opposite poles. At late metaphase, the centromeres and sister chromatids started separating. Subsequently, the sister chromatids and centromeres split finally resulting in dyads. Our observations indicate that bipolar orientation of the sister kinetochores of univalents at the equatorial plate in metaphase I is important for the subsequent bipolar separation of sister chromatids in the first meiotic division. Allopolyploids are common in plants. Wide hybridization, the first step for the origination of allopolyploids, brings divergent genomes from different species together into an amphihaploid hybrid. Because only one set of homologous chromosomes is present, amphihaploids (analogous to haploid plants) are usually sterile due to reduced meiosis. Meiotic nonreduction (meiotic restitution), however, can lead to production of functionally unreduced gametes, and their union immediately generates an amphidiploid (allopolyploid). Meiotic nonreduction is thought to be the

Assessment of the Cytogenetic Damage Induced by Chromium Short-Term Exposure in Root Tip Meristems of Barley Seedlings

Heavy metals are determinant factors in increasing environmental pollution, and chromium is considered to be of highest concern because of its genotoxicity in microorganisms, animals, and humans. Relatively few studies are focused on the injury induced in plant genetic material. Therefore, the main objective of this work was to evaluate the extent of the cytogenetic damage induced in root meristems of barley (Hordeum vulgare L.) after short-term seed exposure to 10, 100, 250, and 500 μM K2Cr2O7 (Cr(VI) concentration is 1.04, 10.39, 25.99, and 51.99 μg ml−1) and 10, 100, 250, and 500 μM CrCl3 (Cr(III) concentration is 0.52, 5.19, 12.99, and 25.99 μg ml−1). Chromium genotoxic potential was proved by significant increases in the rates of the ana-telophase chromosomal aberrations (1.3–2.3 times higher for K2Cr2O7 and 1.7–2.2 times higher for CrCl3, as compared to the control; p < 0.05, p < 0.01) and of metaphase disturbances (5.0–7.5 times more numerous in chromium-treated groups than in control; p < 0.001). The pattern of the chromosomal aberrations is constituted by chromatid bridges, complex aberrations, lagging, and vagrant chromosomes, while the abnormal metaphases are c-like metaphases, sticky metaphases, and metaphases with chromosomes expulsed from equatorial plate. The mitotic indices and the growth of the barley plantlets in the early ontogeny were stimulated by chromium. The changes induced in the frequency of division stages mainly consisted in prophase and telophase accumulation and diminution of metaphase and anaphase proportion.

Different timing and spatial separation of parental chromosomes in intergeneric somatic hybrids between Brassica napus and Orychophragmus violaceus

Experimental and newly formed hybrids and polyploids generated by wide crosses usually show varying degrees of cytological instability. The spatial separation of parental genomes and uniparental chromosome elimination in hybrid cells has been reported in many hybrids from plants and animals. Herein, the behavior of parental genomes in intergeneric somatic hybrids between Brassica napus and Orychophragmus violaceus was analyzed using genomic in situ hybridization (GISH). In mitotic and meiotic cells, the chromosomes from O. violaceus were distinguished from B. napus by their larger size and staining patterns. In interphase nuclei of the hybrid, O. violaceus-labeled chromatin appeared as large heterochromatic blocks that were nonrandomly distributed at prophase, typically distributed toward one side of the nucleus. In pollen mother cells at prophase I of meiosis, O. violaceus chromosomes appeared as one or two deeply stained chromatin blocks that resolved into bivalents at a late stage, after bivalents from B. napus were visible. Thereafter, bivalents of O. violaceus congressed to the equatorial plate and segregated at anaphase I after those from B. napus. The different behavior of O. violaceus chromosomes in the hybrids indicates that they have differential condensation states at interphase and progress later through the cell cycle and meiosis than B. napus chromosomes. This difference in behavior may restrict or prevent the formation of bivalents of mixed genome origin. Differential gene expression of parental alleles including rDNA loci may contribute to their distinct cytological behavior and to the phenotype of hybrids.

Cytological changes in meristematic cells of Allium cepa L. root tip treated with extracts from callus of Catharanthus roseus (L.) G. Don

The effect of an ethanolic extract from callus of &lt;em&gt;Catharanthus roseus&lt;/em&gt; on &lt;em&gt;Allium cepa&lt;/em&gt; root cells divisions was investigated. Two lines: white and green callus, were established on solid B5 medium with IAA 1 mg/l and kinetin 0.1 mg/l. The HPLC analysis of callus extracts showed the presence of indole alkaloids, however not known pharmacologically active alkaloids or derivatives used in semisynthesis (vinblastine, ajmalicine, serpentine, yohimbine, vindoline and catharanthine) have been found. The ethanolic extract of &lt;em&gt;C. roseus&lt;/em&gt; callus inhibited the number of mitoses in &lt;em&gt;Allium cepa&lt;/em&gt; root tip cells. Short (1-3 hours) treatment resulted in an increase in the index of late prophases, with characteristic light spaces, and the index of metaphases with twisted chromosomes forming an equatorial plate or irregular structures of c-metaphases. At the same time, the percentage of anaphases and telophases decreased significantly. Longer treatment of the root tip inhibited mitotic activity, stopping it completely already after 12 hours. Interphase nuclei became at first denser and homogeneous, eventually their structure became , partitioned into zones and formation of chromatin territories, with distinct large nucleoli has been observed. Electron microscope observations revealed well developed rough endoplasmic reticulum and thick, invaginating cell membrane.