Cold stress adversely affects the development and growth of plant and is a serious threat to the sustainability of crop yields. Transcription factors (TF) and hub genes responsible for cold tolerance in barley can be identified to understand the molecular mechanism of Hordeum vulgare responses to cold stress. The present meta-analysis of microarray data exhibited 404 upregulated genes and 642 downregulated genes related to cold stress. The Gene Ontology (GO) enrichment analysis showed significant GO terms common among up and downregulated genes related to cold stress including GO:0005524 (metabolic process), GO:0071704 (organic substance metabolic process), GO:0044550 (secondary metabolite biosynthetic process) and GO:0009987 (cellular process). TFs including TCP, NF-YB and B3 were higher in upregulated metaDEGs; and bHLH, AP2 and bZIP were higher in downregulated meta-DEGs. HORVU. MOREX.r3.2HG0194700 with mitochondrial precursor function and HORVU. MOREX.r3.1HG0055890 with proline oxidaseas function as the candidate hub genes upregulated meta-DEG; and HORVU. MOREX.r3.6HG0592430 with LEA protein function and HORVU. MOREX.r3.5HG0429040 with VQ domain containing protein function as the candidate hub genes downregulated meta-DEG. Finally, the data obtained from the present meta-analysis were compared with the qRT-PCR results of other experimental data and their up and down expression were confirmed. The results of this research might be of help in understanding the cold stress molecular bases and the expression of cold-regulated genes and TFs analyses in genetic modification of agricultural crops. The resistance mechanism for breeding can improve the resistance of cereals against abiotic stress and producing resistant plants.

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.