Metabolome-wise analysis of plants exposed toabiotic stress conditions to identify potential metabolites inducers of cross-tolerance to biotic stressors

Abstract

Plant pathogens are major threats for optimal crop yield and preservation of the harvest. Although plant immune responses are well characterised in isolation, pathogen infections frequently occur in combination with other stress conditions. Importantly, the outcome of plant-pathogen interactions under combinatorial stress is unpredictable as the operating molecular mechanisms differ from those triggered under each individual stressor. Certain abiotic stressors ultimately confer resilience to subsequent pathogen infection, i.e. cross-tolerance, however the network of molecular events involved remains undeciphered. Recent studies suggested that metabolites could retain “stress memory” and modulate combinatorial stress responses, but their potential role in cross-tolerance has been barely investigated. My Marie Skłodowska-Curie project is aimed at identifying changing metabolites after abiotic stress periods that contribute to enhance plant tolerance to pathogens. To this end, comprehensive time-courses for sequential stress were defined to cultivate Arabidopsis plants under nine frequent adverse environmental conditions – namely fluctuations in light intensity, humidity, water availability and temperature - followed by a recovery phase and an eventual pathogen challenge. Metabolome changes of plants were profiled on daily basis using untargeted LC-MS and systemically analysed by means of conditional networks. Network analysis and identification of significantly altered metabolites were used to retrieve central features to cope with abiotic stressors. Complementary, transcriptome analyses were also conducted. Our first results are consistent with the idea that metabolome changes in response to abiotic stressors are persistent overtime, whereas transcriptome changes are reversible. Further investigation on metabolite composition of plants after abiotic stressors uncovered fluctuations in central groups of compounds. The potential relevance of such candidates to modulate immune responses is currently being assessed in planta. Finally, metabolome profiling is being also employed to evaluate potential mechanisms of cross-tolerance in selected species of agronomic interest, i.e., melon, tomato, and rice. Conditional networks will be employed in that case to evaluate conservation and/or particular mechanisms of adaptation for memory stress in species evolutionary distant.