Mechanical Properties of Arabidopsis thaliana Nuclei

The mechanical properties of the nucleus play an important role in the physiology of the cell. For example, mutations in the genes encoding nuclear envelope lamin proteins result in structural changes to the nucleus, and are linked to tissue-specific diseases. While plants lack the lamin proteins that are critical for the mechanical stability of animal cell nuclei, similar coiled-coil proteins LINC1 and LINC2 help to maintain nuclear size and structure in Arabidopsis thaliana; linc1 linc2 double mutants display both reduced nuclear size and altered nuclear morphology. To investigate plant cell nucleus mechanical properties and elucidate the role of LINC proteins in nuclear mechanical stability, nuclei of the model organism Arabidopsis thaliana are examined. Different components of the nucleus (LINC proteins, chromatin, nuclear membranes) are fluorescently labeled and imaged while the nucleus is deformed in a microfluidic device; subsequent quantitative image analysis reveals to what extent the plant cell nuclear envelope behaves as a fluid membrane or a solid-elastic shell. Nuclei, including linc1 and linc2 deletion mutants, are subjected to mechanical forces in microfluidic devices that can precisely control the applied stress to characterize the elasticity of the nucleus. Osmotic manipulations are also performed on trapped protoplasts and isolated nuclei to investigate the effects of varying osmolarity on the shape and structural stability of the nucleus. These experiments provide insight into the physical properties of plant cell nuclei, and ultimately, the link between the physical environment of the nucleus and plant cell physiology.