Lipid-Derived Aldehydes: New Key Mediators of Plant Growth and Stress Responses

SIMPLE SUMMARY: Aldehydes are inevitably produced through non-enzymatic and enzymatic pathways from fatty acids in both normal and stressed conditions. Different fatty acids result in unique aldehydes with carbon chains of different lengths and levels of unsaturation, which determine their functions and reactivities in plants. The detailed description of the formation, toxic effects, and detoxification mechanisms of aldehydes in plants is highlighted in this review. Moreover, the signaling effects of aldehydes are summarized as well. ABSTRACT: Aldehydes, derivatives of lipids, are ubiquitously produced through non-enzymatic and enzymatic pathways in higher plants and participate in many physiological and biological processes. Increasing evidence demonstrates that aldehydes are involved in plants response to many abiotic stresses, such as light, drought, heat and nutrient deficiency. In plant cells, endogenously triggered or exogenously applied high concentrations of aldehydes can damage proteins and nucleic acid, disturb redox homeostasis, and consequently inhibit plant growth; therefore, they are considered cytotoxins. Aldehyde levels are also used as biomarkers to evaluate the health status of plants. Further genetic research shows that several enzymes have strong capacities to detoxify these electrophilic aldehydes. Small molecules, such as carnosine and glutathione, also exhibit the ability to scavenge aldehydes, effectively promoting plant growth. Recently, increasing evidence has shown that certain aldehydes at certain concentrations can upregulate survival genes, activate antioxidant responses, increase defense against pathogens and stimulate plant growth. This review summarizes recent studies of lipid-derived aldehydes in higher plants, mainly focusing on the generation pathway, toxic effects, and detoxification strategies. In addition, the signaling effects of aldehydes in plants are also discussed.