Biology subjects

Drakakaki, G.

Publications and source records attributed to Drakakaki, G..

3 recordsLinked to original sources

bioRxiv2020

NMR spectroscopy analysis reveals an altered metabolic homeostasis in Arabidopsis seedlings treated with a cytokinesis inhibitor

In plant cytokinesis, de novo formation of a cell plate evolving into the new cell wall partitions the cytoplasm of the dividing cell. Cell plate formation involves highly orchestrated vesicle accumulation, fusion, and membrane network maturation supported by the temporary integration of elastic and pliable callose. The small molecule, Endosidin 7 (ES7) arrests late cytokinesis in Arabidopsis by inhibiting callose deposition at the cell plate. Its effect is specific, as it does not broadly affect endomembrane trafficking or cytoskeletal organization. It has emerged as a very valuable tool for dissecting this essential plant process. In order to gain deeper insights regarding its mode of action and the effects of cytokinesis inhibition on overall plant growth, we investigated the effect of ES7 through a nuclear magnetic resonance spectroscopy metabolomics approach. In this case study, profiles of Arabidopsis leaf and root tissues were analyzed at different growth stages and ES7 exposure levels. The results show tissue-specific changes in the plant metabolic profile across a developmental gradient, and the effect that ES7 treatment has on the corresponding metabolome. The ES7 induced profile suggests metabolic compensations in central metabolism pathways in response to cytokinesis inhibition. Further, this study shows that long-term treatment of ES7 disrupts the homeostasis of primary metabolism in Arabidopsis seedlings, likely via alteration of hormonal regulation.

biochemistry↗

bioRxiv2020

Callose deposition is essential for the completion of cytokinesis in the unicellular alga Penium margaritaceum

Cytokinesis in land plants involves the formation of a cell plate that develops into the new cell wall. Callose is a {beta}-1,3 glucan that transiently accumulates at later stages of cell plate development and is thought to stabilize the delicate membrane network of the cell plate as it expands. Cytokinetic callose deposition is currently considered specific to multicellular plant species as it has not been detected in unicellular algae. Here we present callose at the cytokinesis junction of the unicellular charophyte, Penium margaritaceum. Notably, callose deposition at the division plane of P. margaritaceum showed distinct, spatiotemporal patterns that could represent distinct roles of this polymer in cytokinesis and cell wall assembly. Pharmacological inhibition of cytokinetic callose deposition by Endosidin 7 treatment resulted in cytokinesis defects, consistent with the essential role for this polymer in P. margaritaceum cell division. Cell wall deposition and assembly at the isthmus zone was also affected by the absence of callose, demonstrating the dynamic nature of new wall assembly in P. margaritaceum. The identification of candidate callose synthase genes provides molecular evidence for callose biosynthesis in P. margaritaceum. The evolutionary implications of cytokinetic callose in this unicellular Zygnematopycean alga is discussed in the context of the conquest of land by plants. Summary StatementEvolutionarily conserved callose in Penium margaritaceum is essential for the completion of cytokinesis.

cell biology↗

bioRxiv2020

A Biophysical Model for Plant Cell Plate Development

Plant cytokinesis, a fundamental process of plant life, involves de novo formation of a cell plate that partitions the cytoplasm of the dividing cell. Cell plate formation is directed by orchestrated delivery, fusion of cytokinetic vesicles, and membrane maturation to the form the nascent cell wall by the timely deposition of polysaccharides such as callose, cellulose, and crosslinking glycans. In contrast to the role of endomembrane protein regulators the role of polysaccharides, in cell plate development is poorly understood. Callose, a {beta}-1-3 glucan polymer, is transiently accumulated during cell plate expansion to be replaced by cellulose in mature stages. Based on the severity of cytokinesis defects in the absence of callose, it has been proposed that it stabilizes this membrane network structure. However, there is currently no theory to understand its role in cytokinesis. Here we extend the Helfrich free energy model for membranes including a phenomenological spreading force as an "areal pressure" generated by callose and/or other polysaccharides. Regular cell plate development in the model is possible, with suitable bending modulus, for a two-dimensional late stage spreading force parameter of between 2-6pN/nm, an osmotic pressure difference of 2-10kPa, and spontaneous curvature between 0-0.04nm-1. With these conditions, stable membrane conformation sizes and morphologies emerge in concordance with stages of cell plate development. With no spreading force, the cell plate fails to mature properly, corroborating experimental observations of cytokinesis arrest in the absence of callose. To reach a nearly mature cell plate, our model requires the late stage onset that the spreading force coupled with a concurrent loss of spontaneous curvature. A simple model based upon production of callose as a quasi-two-dimensional self-avoiding polymer produces the correct phenomenological form of the spreading force, which will be further refined, since matching to our numbers requires an exceptionally high callose synthesis rate. Significance StatementPlant cell division features the development of a unique membrane network called the cell plate that matures to a cell wall which separates the two daughter cells. During cell plate development, callose, a {beta}-1-3 glucan polymer, is transiently synthesized at the cell plate only to be replaced by cellulose in mature stages. The role for this transient callose accumulation at the cell plate is unknown. It has been suggested that callose provides mechanical stability, as well as a spreading force that widens and expands tubular and fenestrated cell plate structures to aid the maturation of the cell plate. Chemical inhibition of callose deposition results in the failure of cell plate development supporting this hypothesis. This publication establishes the need for a spreading force in cell plate development using a biophysical model that predicts cell plate development in the presence and the absence of this force. Such models can potentially be used to decipher for the transition/maturation of membrane networks upon the deposition of polysaccharide polymers.

biophysics↗