Plasma membrane fluidity as a potential sensor of cold stress in plants: Insights from comparing cold-tolerant and cold-sensitive tomato species

Cold stress is a critical factor limiting the productivity of agricultural crops, including tomatoes. Despite significant progress in the study of the molecular mechanisms of cold tolerance, the primary sensors involved in the effects of low temperatures on higher plants remain unknown. In this study, a comparative analysis of two species of the genus Solanum, cold-sensitive S. lycopersicum and cold-tolerant wild S. lycopersicoides, has been carried out to identify the relationships among plasma membrane fluidity, cold response gene expression (CBF/COR), and the stability of the photosynthetic apparatus under cold stress. Сold tolerance was assessed by electrolyte leakage and the effective quantum yield of photosystem II (Y(II)). The molecular response was monitored by measuring CBF1-3 and COR413 gene expression via real-time PCR. The plasma membrane fluidity was assayed by electron paramagnetic resonance (EPR) using a lipid soluble spin probe 5-doxil stearate, and the membrane fatty acid composition was determined via gas‒liquid chromatography‒mass spectrometry. Compared with S. lycopersicum, S. lycopersicoides presented lower electrolyte leakage, more stable photosystem II functions, and altered CBF/COR gene expression dynamics. The membranes of the resistant species retained their fluidity longer at lower temperatures, which correlated with a higher content of triene fatty acids in the plasma membrane. These results support the hypothesis that plasma membrane fluidity plays an important role in the initiation of the cold response and highlight the contribution of membrane properties to the physiological and molecular resistance of plants to cold.