Molecular mechanism of drought stress tolerance in barley (Hordeum vulgare L.) via a combined analysis of the transcriptome data

One of the main issues addressed by phytology in recent years has been plant tolerance mechanisms for abiotic stress. No combined analysis has been made to identify the genes involved in drought stress tolerance. The meta-analysis of microarray data related to drought stress was analysed by the R software packages and showed 3 029 upregulated genes and 3 017 downregulated genes. The upregulated genes were mostly related to the drought tolerance protein, abiotic stress response, and the Cys2His2 Zinc Finger Transcription Factor (C2H2 zinc finger TF). The downregulated genes were mainly related to the late embryogenesis abundant protein, abiotic stress response, and the basic leucine zipper (bZIP) TF. The common gene ontology (GO) terms in the upregulated and downregulated genes were mainly related to the metabolic process, response to stimulus, cellular metabolic process, and photorespiration. The up and down meta-differential expressed genes (meta-DEGs) mainly belonged to the those following Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways including: the biosynthesis of secondary metabolites, plant hormone signal transduction, mitogen-activated protein kinase (MAPK) signalling pathway, and RNA degradation. Moreover, in the upregulated and downregulated genes, the TFs with a high percentage mainly belonged to the Teosinte branched1/Cincinnata/proliferating cell factor (TCP), basic helix loop-helix (bHLH) and bZIP. Next, the hub upregulated genes were mainly related to the thiamine biosynthesis protein thiC, 4-hydroxyphenylpyruvate dioxygenase, ribose-5-phosphate isomerase precursor and heat shock protein. The hub downregulated genes were mainly associated with the elongation factor Ts, aldehyde dehydrogenase, and trigger factor. Finally, the data from the present meta-analysis were compared with previous studies on the qRT-PCR results and their up and down expressions were confirmed. Based on the findings of the current study, novel insights into the drought stress molecular response can be provided and various candidate genes can be introduced for barley drought stress tolerance breeding.