Leaf specialized metabolome of Quercus pubescens exposed to amplified drought

National audienceThe intensification of summer drought expected with climate change in the Mediterranean region can induce metabolism modifications in plants to help them cope with such conditions. In the long term, these modification may impact diversity and global ecosystem functioning.-an in situ experimental site, equipped with a rainfall exclusion device, allowed reduction of natural rainfall by 30% over the tree canopy.-leaves of ND and AD plots were collected in spring, summer and fall during 3 years (2 nd , 3 rd and 4 th years of drought application).-a targeted approach was used to focus on phenolic metabolites.-an untargeted approach permitted to study a broader metabolome variation according to drought. Targeted and untargeted approaches permitted to demonstrate a time lag of the phenylpropanoid pathway over leaf phenology when trees were exposed to drought. Quercetins, catechins and myricetins, specific to summer leaves were down-regulated to favor the biosynthesis of kaempferols, specific to automnal leaves. Further studies would be necessary to understand how this time lag phenology may impact ecosystem functioning. Three of them might be linked to rhododendrin (with apiosyl rhododendrin and galloyl rhododendrin / waiting for co-injection of standard to be confirmed). Untargeted approach: The effect of drought on Quercus metabolome was weak (ns in 2013 ; p < 0.05 for 2014 and 2015) whereas metabolome is mainly driven by seasons (p < 0.001 for all years, two-ways permanova). Targeted approach: a drought effect was observed for both years (p < 0.05), while the metabolomic profiles were mainly influenced by phenology (p < 0.001, two-ways permanova)