Evaluation of Setaria viridis physiological and gene expression responses to distinct water-deficit conditions

Setaria viridis, a C₄ monocot, was proposed as a model plant for studies on the response to stress conditions. Water-deficit ranks among the top three most devastating stresses and its importance will likely increase in the scenario of climate change. The aim of this work was to evaluate physiological and molecular water-deficit responses of S. viridis subjected to different conditions. Principal component analysis highlighted the physiological differences between vegetative and reproductive stages of S. viridis, as well as the differences between two methods of water-deficit induction: polyethylene glycol and air-drying. Network interactions were observed in distinct developmental stages and water-deficit induction methods tested, allowing classification of root and shoot fresh weight and non-photochemical quenching as the best physiological parameters to group the networks. Variations in the gene expression patterns of delta 1-pyrroline-5-carboxylate synthase 2 (SvP5CS2), Dehydrin 1 (SvDHN1) and the transcription factors WRKY DNA-binding domain 1 (SvWRKY1), dehydration-responsive element-binding protein 1 class C (SvDREB1C) and NAC protein 6 (SvNAC6) were observed. Among these genes, it was observed two expression patterns predominant during water-deficit: inducible (SvDHN1 and SvNAC6) and repressed (SvP5CS2, SvWRKY1 and SvDREB1C) genes. SvDHN1 showed the highest expression level in all the conditions tested. PEG treatment during the reproductive stage promoted the upregulation of the five marker genes in roots. The discriminative analysis suggested that the physiological and molecular responses in S. viridis adjusted according to the evaluated water-deficit conditions, especially after PEG treatments, indicating that the PEG method of water-deficit may better replicate field conditions.