Multi-omic profiles of Sorghum genotypes with contrasting heat tolerance connect pathways related to thermotolerance

Understanding how crop varieties acclimate to elevated temperatures is key to priming them for future climates. Here, we imposed a 6 d heat shock treatment (reaching 45 degrees C) on two genotypes of Sorghum bicolor [one sensitive to heat shock (Sen) and one tolerant (Tol)] growing under two temperature regimes, and carried out a suite of measurements before and during the heat shock. Sen consistently reduced photosynthetic functioning during heat shock, while Tol increased its photosynthetic rate. Higher abundance of heat shock protein transcripts and metabolites related to heat tolerance were noted for Tol when compared with Sen both before and during heat shock, which can be attributed to constitutive and inducible responses to elevated temperatures. In addition, important changes in metabolic pathways were clearly identified for Tol during heat shock (including up-regulation of raffinose family oligosaccharides and down-regulation of the gamma-aminobutyric acid catalytic pathway), even as the concentration of hexose sugars became depleted. We infer Tol was able to tolerate elevated temperatures due to up-regulation of osmoprotectants, chaperones, and reactive oxygen species scavengers and by the suppression of SnRK1 via transcripts and metabolites during heat shock. Our results highlight potential targets for attributes of high temperature tolerance that can be utilized in future breeding trials.