Identifying the Genetic Networks Involved in the Response of Sunflower to Drought

Identifying the connections between molecular and physiological processes underlying the genetic diversity of drought stress responses in plants is particularly relevant for basic and applied science. Drought stress response involves a large number of molecular pathways and subsequent physiological processes. Therefore, it is a complex trait that can be decomposed at the molecular level and studied as a systems biology model.

Our approach first identified, without a priori knowledge, a Gene-Phenotype network comprises 1263 transcripts and 6 morpho-physiological traits. We characterized the correlations between traits and gene expression if they originate from genotypic, environment, and/or genotype environment interaction effects and if they were acting at mild or severe drought stress intensities.

Our next goal was to decipher the genetic control of these morpho-physiological traits, and therefore of the sunflower drought response. To achieve this, we performed a Genome Wide Association Study on the expression levels of 86 transcripts previously associated to the different morpho-physiological traits. This study performed in agronomic conditions on a sunflower core-collection allowed us to identify around 50 genomic regions controlling 42 gene expressions. Thanks to a newly developed biomarker, we characterized if this genetic control was under the influence of the environment.

All together, this combination of global approaches revealed different molecular pathways that are genetically variable and that transduce or not the environmental signal. In addition, it proved to be successful to decompose the complex morpho-physiological responses into more heritable traits (i.e. gene expression) and identify general properties of the drought stress response in sunflower.