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Understanding Symbiotic Diversity: aCandidate Gene approach

Final Report Summary - SYM'S GENE (Understanding Symbiotic Diversity: aCandidate Gene approach)

Interaction between plant root and arbuscular mycorrhiza (AMF) is a crucial symbiosis in nature and present in almost all crops. In addressing plant responses to stress, this research shifts the focus from the host to the symbiotic unit. By recognizing symbiosis to be a major player in evolution, the interplay is valued between the adaptive regulation of host and symbionts metabolisms. This view impacts directly on agricultural practices and in plant breeding, particularly when selecting for agronomic target traits.

The research aimed to address the ecological efficiency and specificity of AM fungi community in natural populations across environments in a single selected host (wild carrots). It started from the perspective that the alternative oxidase (AOX) was linked to all kinds of abiotic and biotic stress reactions in various organisms and thus habitat-adapted distribution would likely correlate with AOX polymorphisms. We found high variability of DcAOX1 in the populations of wild carrot sampled across a West-European environmental gradient but no direct relation with the climatic conditions or with physical distance. This gene might indeed be under positive selection as hypothesized, but if present it only acts on some specific populations. Nonetheless, a highly polymorphic intronic insertion of the DcAOX1 gene, with associated SSRs, is promising as source of molecular markers. The relation between host population diversity and symbiotic biodiversity is being analyzed and this will likely give insights into symbiont specificity towards habitat-adaptation, even though no relation with host AOX polymorphisms was clear. Two wild carrot populations were highlighted by their level of differentiation at the AOX gene, and were thus selected as promising hot spots of specific functional diversity. The population of the Iberian Peninsula is the one inhabiting in a climate with higher temperatures and lower humidity, and was hence selected for a genome-wide analysis through whole transcriptome shotgun sequencing (RNA-Seq) aiming to elucidate on the mechanisms of drought tolerance of the plant alone and symbiont (AMF) induced. Considering global climate change, incidence of combined drought and heat stress is likely to increase. The Mediterranean region is predicted to be one of the most affected, where climate change may add to existing problems of desertification, water scarcity and food production.

Overall, the research will lead to better understanding of evolutionary processes that shape the composition of the symbiosis and of the benefit of diversity to crop productivity. The approach is interdisciplinary: physiology, ecology and evolutionary genetic methodologies. There is high commercial interest in appropriate breeding strategies based on efficient genotype-mycorrhiza as they can promote, a.o. a more sustainable use of phosphorus in crops and minimize associated biodiversity losses, and mitigate the impacts of global climate change on agricultural and native plant communities.