Brassinosteroid-lipid membrane interaction under low and high temperature stress in model systems

Area of Science:

• Plant Physiology
• Biochemistry
• Membrane Biophysics

Background:

• Brassinosteroids (BRs) are plant hormones known to influence various physiological processes.
• Previous studies showed BRs alter physicochemical properties of isolated plant lipids.
• This study investigates specific BRs, homocastasterone (HCS) and castasterone (CS), under conditions mimicking low-temperature plant growth.

Purpose of the Study:

• To investigate the influence of HCS and CS on the polar and hydrophobic membrane properties.
• To elucidate the effects of these brassinosteroids on model lipid systems.

Main Methods:

• Utilized electrokinetic potential measurements to assess surface charge modifications.
• Employed Electron Paramagnetic Resonance (EPR) and Langmuir techniques to study hydrophobic interactions.
• Calculated physicochemical parameters and Gibbs free energy of excess.

Main Results:

• Both HCS and CS decreased the negative surface charge of lipid membranes, impacting polar substance interactions.
• EPR and Langmuir techniques revealed significant alterations in the hydrophobic core of the membranes.
• Physicochemical parameters and Gibbs free energy calculations quantified these structural changes.

Conclusions:

• HCS and CS modify both hydrophilic and hydrophobic membrane properties, with HCS showing a greater effect.
• These modifications likely contribute to maintaining membrane stability under temperature stress.
• Increased BR levels, particularly HCS, during cooling may be crucial for membrane functionality despite temperature fluctuations.