# Dynamic Imaging of Lipid Order and Heterogeneous Microviscosity in Mitochondrial Membranes of Potato Tubers Under Abiotic Stress

## TL;DR

This study uses fluorescent imaging to show how hyperosmotic stress affects the microviscosity and lipid order in potato mitochondria, revealing new membrane domains linked to stress resistance.

## Contribution

The first mapping of mitochondrial membrane microviscosity dynamics and identification of stress-induced lipid-ordered domains in plant cells.

## Key findings

- Hyperosmotic stress increases lipid order in mitochondrial membrane domains, as shown by Laurdan GP values.
- Stressed mitochondria show decreased substrate oxidation and respiratory control but increased MitoTracker Orange fluorescence.
- Membrane microviscosity changes under stress suggest a role for raft-like domains in plant stress resistance.

## Abstract

Microviscosity and lipid order are the main parameters characterizing the phase states of the membrane. Variations in microviscosity and lipid composition in a living cell may indicate serious disturbances, including various kinds of stress. In this work, the effect of hyperosmotic stress on the microviscosity of mitochondrial membranes was investigated, using potato (Solanum tuberosum L.) tuber mitochondria. The microviscosity of mitochondrial membranes isolated from check and stressed (9 days at 34–36 °C) tubers was estimated by determining the generalized polarization (GP) values using a Laurdan fluorescent probe in confocal microscopy studies. It was revealed that the GP distribution in mitochondria isolated from stressed tubers contained new component-characterizing membrane domains with an increased lipid order compared to the rest of the membrane. We have mapped the microviscosity of mitochondrial membranes for the first time and observed the dynamics of the membrane microviscosity of an individual mitochondrion. The hyperosmotic stress significantly influences the functional state of potato mitochondria, decreasing the substrate oxidation rate and respiratory control coefficient but increasing MitoTracker Orange fluorescence. Under hyperosmotic stress, the microviscosity of mitochondrial membranes changes, and membrane domains with increased lipid order are formed. The revealed changes open up prospects for further research on the participation of raft-like microdomains of mitochondria in plant resistance to stress factors.