Water-stressed sunflower transcriptome analysis revealed important molecular markers involved in drought stress response and tolerance

Water stress is considered one of the most important factors limiting worldwide agricultural productivity and efficiency. Although sunflower (Helianthus annuus L.) is a deep-rooted crop, water stress strongly reduces its productivity. A holistic approach that integrates physiological, biochemical and molecular genetic tools could provide opportunities for breeding novel genotypes with stable yield under water-deficit conditions. In this study, we have studied the responses of several Helianthus annuus genotypes, in water stress conditions, using genomics (RNA-seq and quantitative RT-PCR), physiological (growth, water statute, stomatal conduction evaluations, and transpiration rate) and biochemical analyses (LC-MS). Our physiological analyses indicated a sunflower genotype-dependent water stress response. This variability in the water stress response could be observed transcriptomically with the identification of water stress core genes, as well as genes characteristic of tolerance and/or sensitivity to a water deficit. From these genes, we identified several components involved in abscisic acid synthesis and signaling (NCED3, NCED5, ABII and PYL4), which must be involved in drought tolerance. Under well-watered conditions, we subsequently detected higher abscisic acid content in leaves of the sensitive genotypes. We propose that sunflower water stress tolerance is correlated with a transcriptome fine-tuning leading to an efficient activation of ABA-dependent genes and not by ABA overproduction.