GSE98893
Apple fruit superficial scald resistance mediated by ethylene inhibition is associated with diverse metabolic processes
Fruits stored at low temperature for long time can undergo to different type of chilling injuries. In apple, superficial scald represents one of the most serious physiopathy. The typical symptoms of this disorder are represented by the development of important discoloration and black patches on the fruit exocarp. Although this phenomenon has been historically related to a-farnesene, its etiology and physiology are not yet fully disclosed. In the attempt to elucidate the regulating mechanism of its development and prevention, a multidisciplinary survey was performed, integrating different level of metabolite screening (volatiles, polyphenols and lipids) with a large-scale transcriptomic analysis. The comparison between scalded and non-scalded apples (treated with an ethylene competitor) revealed that the prevention of superficial scald is associated with the triggering of cold acclimation-related processes. The interference at the ethylene receptor level stimulates the production of antioxidant compounds to scavenge reactive oxygen species (ROS), the synthesis of unsaturated fatty acids to stabilize plastid and vacuole membranes against cold temperature and the accumulation of sugar alcohols with important cryoprotectant roles, such as sorbitol. The accumulation pattern of this polyalcohol was also consistent with the expression profile of MdS6PDH. Moreover, the overexpression of this gene in transgenic line of Arabidopsis thaliana plants provided functional validation of its involvement in the biosynthetic pathway of sorbitol and elucidated its role in the cold acclimation and freezing tolerance process. Overall design: RNA-Seq analysis of 5 samples of apple exocarp. T0 (control), T2_CTRL (2 months of cold storage in control condition), T2+7_CTRL (7 days of shelf-life after 2 months of cold storage in control condition), T2_MCP (2 months of cold storage treated with 1-MCP), T2+7_MCP (7 days of shelf-life after 2 months of cold storage treated with 1-MCP). Each sample was replicated three times.