Detecting Early Signs of Heat and Drought Stress in Phoenix dactylifera (Date Palm)

Phoenix dactylifera seedlings were exposed to heat, drought and combined heat & drought conditions in growth chambers. Leaf samples were collected for total RNA isolation (RNAseq, Illumina HiSeq 1000), and water soluble metabolites. The RNAseq of four biological replicates (two individuals per replicate) were compared against the control condition. Transcriptomics data suggests the combine heat and drought resembled heat response, whereas drought resembled more to control. The hallmarks of heat stress were visible in the transcriptomics data, such as protein misfolding, response to hydrogen peroxide and cell wall modification, as well as ABA signaling in the case of drought. Since the plants were exposed to the stress for several days before harvesting, the early signs of heat stress such as calcium and NO signaling were not detected anymore. In addition, data suggest a significant enrichment of circadian rhythm motifs in the differentially expressed genes in heat and combined heat and drought stresses, suggesting new stress avoidance strategies.