ARTICLE | doi:10.20944/preprints202002.0322.v1
Online: 23 February 2020 (12:48:24 CET)
Multinucleate cells can be produced in Dictyostelium by electric-pulse induced fusion. In these cells unilateral cleavage furrows are formed at spaces between areas that are controlled by aster microtubules. A peculiarity of unilateral cleavage furrows is their propensity to join laterally with other furrows into rings to form constrictions. This means, cytokinesis is biphasic in multinucleate cells, the final abscission of daughter cells being independent of the initial direction of furrow progression. Myosin-II and the actin-filament cross-linking protein cortexillin accumulate in the unilateral furrows, as they do in the normal cleavage furrows of mononucleate cells. Myosin-II is not essential for cytokinesis, but stabilizes and confines the position of the cleavage furrows.
ARTICLE | doi:10.20944/preprints202101.0226.v1
Subject: Life Sciences, Biochemistry Keywords: Arabidopsis thaliana; callose; cell plate; cross wall; cytokinesis; homogalacturonans; katanin; KNOLLE syntaxin; microtubules; phragmoplast
Online: 12 January 2021 (15:13:01 CET)
Cytokinesis is accomplished in higher plants by the phragmoplast, creating and conducting the cell plate, to separate daughter nuclei by a new cell wall. The microtubule-severing enzyme p60-katanin plays an important role in the centrifugal expansion and timely disappearance of phragmoplast microtubules. Consequently, aberrant structure and delayed expansion rate of the phragmoplast occur in p60-katanin mutants. Here, the consequences of p60-katanin malfunction in cell plate/daughter wall formation were investigated by transmission electron microscopy (TEM), while deviations in the chemical composition of cell plate/new cell wall were identified by immunolabeling and confocal microscopy, in root cells of the fra2 Arabidopsis thaliana mutant. It was found that, apart from defective phragmoplast microtubule organization, cell plates/new cell walls appeared also faulty in structure, being unevenly thick and perforated by large gaps. In addition, demethylesterified homogalacturonans were prematurely present in fra2 cell plates, while callose content was significantly lower than in the wild-type. Furthermore, KNOLLE syntaxin disappeared from newly formed cell walls in fra2 earlier than in the wild-type. Taken together, these observations indicate that delayed cytokinesis, due to faulty phragmoplast organization and expansion, results in a loss of synchronization between cell plate growth and its chemical maturation.