A yeast osmotic reporter system as a tool to identify biostimulant for plant drought stress tolerance

In the context of global warming, water availability is a major concern and strategies aiming at the protection of this vital resource without reduction of crop yield are of particular interest. In this regard, a system able to identify new biostimulants to improve plant drought tolerance could constitute a powerful tool. In poplar, previous studies have characterized a full signaling pathway that could be involved in osmosensing. This pathway corresponds to a multistep phosphorelay initiated by two transmembrane Histidine-aspartate Kinase receptors, HK1a and HK1b. We hypothesized that extracts or compounds that can modulate the activity of these receptors could trigger plant response to drought, acting as potential biostimulant to improve plant tolerance to this stress. To test this hypothesis, we created a yeast-based fluorescent reporter system for osmosensing. We demonstrated the functionality and the specificity of such a system, acting as an osmotic biosensor. As an example of application, the screening of 24 different extracts of poplar leaves was performed in this reporter system and two extracts were selected. These extracts were tested on two cultivated plant species under drought stress condition and showed a positive effect on plant growth, indicating a potential effect as biostimulant for drought stress tolerance. A chemical analysis of these extracts revealed interesting molecules to be further explored. Overall, this study provides a promising approach for a fast and cost-effective identification of potential biostimulant compounds able to enhance plant tolerance to drought. • Creation of a fluorescent yeast osmotic reporter system with poplar HK receptors. • Obtention of a biosensor able to select biostimulant for plant drought tolerance. • Screening of 24 leaf extracts and selection of two extracts for biostimulant tests. • Growth improvement under drought stress for the two treated horticultural species. • A promising approach for a fast and cost-effective identification of biostimulants.