The viscoelastic properties of Nicotiana tabacum BY-2 suspension cell lines adapted to high osmolarity

To survive and grow, plant cells must regulate the properties of their cellular microenvironment in response to ever changing external factors. How the biomechanical balance across the cell’s internal structures is established and maintained during environmental variations remains a nurturing question. To provide insight into this issue we used two micro-mechanical imaging techniques, namely Brillouin light scattering and BODIPY-based molecular rotors Fluorescence Lifetime Imaging, to study Nicotiana tabacum suspension BY-2 cells long-term adapted to high concentrations of NaCl and mannitol. We discuss our results in terms of molecular crowding in cytoplasm and vacuoles, as well as tension in plasma membrane. The viscoelastic behavior was elucidated relative to cells external environments revealing the difference between the responses of cytoplasm and vacuole in the adapted cells. To understand how sudden changes in osmolarity affect cellular mechanics, the response of control and already adapted cells to further short-term osmotic stimulus was also examined. The applied correlative approach provides evidence that adaptation to hyperosmotic stress leads to different ratios of protoplast and environmental qualities that help to maintain cell integrity. Presented results demonstrate that the viscoelastic properties of protoplasts are an element of plant cells adaptation to high osmolarity.