Cytogenetical effects of aluminum on root meristem cells of Helianthus annuus L.

Abstract

Different aluminum concentrations (5, 50, and 100 μM), as well as different exposure times (24, 48, and 72 h), were applied to investigate cytogenetical alterations in sunfl ower (Helianthus annuus L.) meristem cells. Nucleolin was also examined under aluminum stress using silver-staining method and indirect immunofl uorescent method. Results showed that the mitotic index decreased progressively when either aluminum concentration or exposure time increased. C-mitosis, anaphase bridges, and chromosome stickiness were observed in the aluminum treated root tip cells. Some particulates containing the argyrophilic NORassociated proteins were distributed in the nucleus of the root-tip cells, and the amount of this particulate material progressively increased with increasing exposure time. Finally, the nucleolar material was extruded from the nucleus into the cytoplasm. The result also indicated the nucleolar protein nucleolin was translocated from nucleolus to nucleoplasm and cytoplasm, that presence of 50 μM of aluminum for 48 h, suggesting that aluminum disturbed rRNA synthesis and induced the abnormal cellular location of nucleolar protein. The strongly toxic effect of aluminum on the nucleolus can inhibit or stop mitosis, and consequently inhibit root growth. Keywords: aluminum, cytogenetical alterations, mitosis, nucleolin, sunfl ower.Resumen: Diferentes concentraciones de aluminio (5, 50 y 100 μM) y diferentes tiempos de exposición (24, 48 y 72 h) se aplicaron a células meristemáticas de girasol (Helianthus annuus L.), para investigar las alteraciones citogenéticas, en particular, dilucidar sobre la nucleolina. La nucleolina fue estudiada bajo el estrés por aluminio, utilizando el método de tinción con plata y el método de inmunofl uorescencia indirecta. Los resultados mostraron que el índice mitótico disminuyó progresivamente a medida que aumentó la concentración de aluminio o el tiempo de exposición. Se observaron C-mitosis, puentes en la anafase y rigidez en los cromosomas en todas las células de la punta de la raíz tratadas con aluminio. Algunas partículas contienen argirófi las NOR asociadas a proteínas distribuidas en el núcleo de las células del ápice de la raíz. La cantidad de este material granulado aumentó progresivamente a medida que aumentó el tiempo de exposición. Finalmente, el material nucleolar se expulsó desde el núcleo hacia el citoplasma. El resultado también indica que, en presencia de 50 μM de aluminio por 48 h, la proteína nucleolina se transloca desde el nucleolo al nucleoplasma y citoplasma, lo que sugiere que el aluminio altera la síntesis de ARNr e induce la localización celular anormal de la proteína nucleolar. El fuerte efecto tóxico de aluminio en el nucléolo puede inhibir o detener la mitosis, y por consiguiente, inhibir el crecimiento de la raíz.

Cytotoxicity and genotoxicity effects of water boiled in aluminum vessels on Allium cepa root tip cells

“…It should be noted that increase in MI and ProI by water sample from the examined pots was also observed when these indexes in control were compared to the average of that from treated groups. These increases in MI and ProI which could be indicative of a positive effect of Al on mitosis, is in agreement with previous studies showed mitotic stimulatory effect of Al at low concentration and short exposure time on cultured human blood and root tip cells of Helianthus annuus [17, 20]. In spite of evidences which support the possible health toxicity of Al, this metal has been shown to be likely nutritionally essential, and its deprivation lead to depressed growth in animals; although a possible required amount for Al in animal deficiency experiments have not been exactly revealed [21].…”

ATR, a DNA Damage Signaling Kinase, Is Involved in Aluminum Response in Barley

“…Our previous work performed for the same genotype treated with aluminum in Hoagland solution has shown that Al treatment significantly reduced the mitotic activity of the root tip cells (Jaskowiak et al, 2018). Similar results were obtained in Al studies of other species, for example Helianthus annuus (Kumar and Srivastava, 2006; Li et al, 2015), Vicia faba (Zhang et al, 2018), and Allium cepa (Qin et al, 2010). Nonetheless, the root meristematic cells of the barley hvatr.g mutant studied here were dividing despite the presence of this genotoxic agent in the medium, which further increased the level of DNA damage observed in control conditions.…”

Comparative Inter- and IntraSpecies Transcriptomics Revealed Key Differential Pathways Associated With Aluminium Stress Tolerance in Lentil

“…Chromosomal aberrations due to disruptions in mitotic cycles of cells can explain the reduced root growth under Al stress conditions. Similar results were also reported by Li et al ( 2015 ) and Zhang et al (2014), who also observed chromosome bridges at anaphase and sticky chromosomes in Al 3+ -treated root tip cells of sunflower and Pinus , respectively. Similarly, Jaskowiak et al ( 2018 ) observed that Al stress significantly reduced the mitotic activity in root tip cells of barley and induced micronuclei in the cells.…”

“…These ions also affect the cellular division process in the root tip meristem; which is immediately subdued under Al-stress conditions (Arunakumara et al, 2013 ). Toxic Al 3+ ions cause chromosomal abnormalities such as bridges, chromosome stickiness, and reduced mitotic activities in root tips that leads to reduced root tip growth, resulting in brownish, stubby, and brittle roots (Zhang et al, 2014b ; Li et al, 2015 ; Jaskowiak et al, 2018 ). Reduced root biomass results in diminished uptake of nutrients and water from the soil.…”