Genetic basis of interspecific differences in resistance to drought stress of the sister species Arabidopsis halleri and A. lyrata

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Water limitation is one of the most important factors limiting crop productivity worldwide. To design sustainable strategies to optimize crop resistance to drought, much can be learned from comparing natural species with diverse ecologies. Indeed, in their natural habitat, species have optimized their strategies to survive drought without compromising overall plant fitness. Previous work in our laboratory has shown that the two species A. lyrata and A. halleri differ in their ecology as well as in their ability to activate avoidance and tolerance mechanisms in response to missing precipitation. We have shown that both the drought-tolerant A. lyrata and the drought-sensitive A. halleri have considerably reshaped their transcriptome. We further collected evidence that the two species differ in both constitutive and drought responsive metabolite levels. We now have to establish functional genetic links between phenotypic, metabolic or transcriptional differences between species and the actual ability of plants to withstand drought stress. To this end, we have developed interspecific back-cross populations. We will leverage these populations to map the genetic basis of interspecific differences in drought reactions. We will further use a bulk-segregant approach to determine gene expression and metabolic modifications associating with improved survival to drought stress. It will help differentiate stress-responsive genes that manifest a state of stress from those that actively contribute to restore homeostasis and promote resistance to drought. This will further validate the role played by functions that have been previously reported to be the target of polygenic selection. Finally, we propose to relate the genetic variation segregating in this interspecific population to global descriptors of ecological diversity, which should help transfer knowledge from the well-known Arabidopsis genus to other species and genera of major ecological or agricultural relevance. On the long term, we believe that the knowledge gained in this study has the potential to bring seminal information for the design of sustainable strategies for improving drought tolerance in crops.