Drought-induced molecular changes in crown of various barley phytohormone mutants_Supplementary Materials

One of the main signal transduction pathways that modulate plant growth and stress responses, including drought, is the action of phytohormones. Recent advances in omics approaches have facilitated the exploration of plant genomes. However, the molecular mechanisms underlying the response in the crown of barley, which plays an essential role in plant performance under stress conditions and regeneration after stress treatment, remain largely unclear. Here, we present for the first time a comprehensive study focusing on the drought-induced molecular reactions of the crowns of different barley phytohormone mutants. Large-scale analyses at the transcriptomic, proteomic, and hormonal levels were conducted using gibberellins-biosynthesis, brassinosteroids-signaling, and strigolactones-signaling mutants as well as reference genotypes. A combined analysis of the mRNA, protein, and hormone levels was performed. Finally, detailed phenotypic evaluation was conducted. The obtained results clearly demonstrated that hormonal disorders caused by mutations in the HvGA20ox2, HvBRI1, and HvD14 genes affected the multifaceted reaction of crowns to drought, although the expression of these genes was not induced by stress. The study further detected not only genes and proteins that were involved in the drought response and reacted specifically in mutants compared to the reaction of reference genotypes and vice versa, but also the candidates that may underlie the genotype-universal stress response. Furthermore, candidate genes involved in phytohormonal interactions during the drought response were identified. We also found that the interplay between hormones, especially gibberellins and auxins as well as strigolactones and cytokinins, may be associated with the regulation of branching in crowns exposed to drought. Overall, the present study provides novel insights into the molecular drought-induced responses that occur in barley crowns.