Drought stress response of Bassia dasyphylla determined by leaf structure, physiology, and transcriptome analyses

To explore the structural, physiological, and molecular responses mechanism of Bassia dasyphylla to drought stress, the anatomical structure, physiological indices, and transcriptomics were determined on leaves treated with different drought stress gradients. Drought stress caused a significant decrease in water-aqueous tissue (P < 0.05) and significant increases in leaf and epidermis thickness at 7 d. Proline content was the highest at 21 d under drought stress (P < 0.05), increased by 24.32% in leaves and 84.58% in epidermis (P < 0.05). The proline content was the highest at 21 d under drought stress (P < 0.05), as was H₂O₂ at 14 and 21 d under drought stress (P < 0.05). The activity of superoxide dismutase (SOD) increased significantly at 21 and 28 d under drought stress (P < 0.05). The activity of peroxidase (POD) activity was maximum at 14 d (P < 0.05) at 38.08 U·g⁻¹. Compared with 0 d, there were 1 860, 2 781, 1 550, and 819 differentially expressed genes (DEGs) under drought stress at 7, 14, 21, and 28 d, respectively. DEGs were significantly enriched in gene ontology terms, including organonitrogen compound metabolic process, oxidative phosphorylation, defense response, and ATP metabolic process. DEGs were enriched considerably in the Kyoto Encyclopedia of Genes and Genomes pathways, such as oxidative phosphorylation, proteasome, ribosome, and spliceosome. Analysis of DEGs of abiotic stress-related pathways showed that genes for stress-sensing receptor kinases (heat shock, drought/salt stress, and wound-inducing proteins); antioxidant oxidase-related genes including CCS, POD, and others; signal pathway genes (Ca²⁺, mitogen-activated protein kinase, and others), genes for transcription factors including ERF, bZIP, MYB, and others; and genes for hormone signaling pathways, cell wall synthesis, protein degradation, and secondary metabolite pathways were involved in drought stress response regulation. The results will provide reference data for the mining and utilizing drought resistance gene resources of B. dasyphylla.