Large scale analysis of leaf gene expression upon treatment of apple grafted scions with acibenzolar-S-methyl or water at 20 or 35°C

Investigation of whole genome gene expression level changes in the youngest expanded leaves of GDDH13 grafted scions either sprayed with reverse osmosis water or acibenzolar-S-methyl (ASM) either exposed to control temperature (21°C/day ; 18°C/night) or three successive heat days (35°C for 4 h during the day ; 18°C/night). The morning of the third heat day, treatment was performed by spraying to runoff (with a pressurized hand sprayer) with the commercial product Bion 50 WG (Syngenta, Basel, Switzerland; 50% of ASM) prepared in reverse osmosis water at a final concentration of 0.4 g/L. All plants were then returned to control thermal conditions (21°C/day ; 18°C/night) for 2 days. The youngest developped leaf of each plant was sampled 72 hours after the treatment. A total of 8 samples were associatied as pairs to perform 4 competitive hybridisations, including dye switchs. Biological replicates are from 2 independantly grown apple plant series. These comparisons allowed to determine the impact of ASM on apple gene expression at control temperature, its impact at high temperature (35°C), as well as the impact of high temperature on water-treated plants or ASM-treated plants.