A Biophysical Model of Intermediate Phases in Developing Cell Plates.*

Plant cell cytokinesis is a fascinating process that involves the formation of a cell plate via a homotypic fusion of vesicles. Cell plate formation depends on organized vesicle delivery, accumulation, fusion, and membrane maturation, along with the timely deposition of polysaccharides such as callose, cellulose, and cross-linking glycans. One unanswered question is the role of callose in cell plate formation¹. We hypothesize that callose deposition produces an anisotropic driving force that acts along the periphery of the cell plate. A biophysical model based on the Helfrich general shape equation² is presented to explain flat regions within the developing cell plate. The increase in callose deposits is reflected in the increase of membrane area and the anisotropic driving force. By postulating a force per callose polymer of 0.25-0.3pN, as well as an osmotic pressure difference of 0.01MPa and a finite surface tension of 0.0014N/m, we can achieve stable disks of radius 80-100nm, in agreement with observed sizes corresponding to intermediate stages of plate development.

References:
1. Drakakaki et al. Plant Physiology vol. 165,3 (2014): 1019-1034.
2. Helfrich, W. (1973) Z. Naturforsch., C 28, 693–703.