Identification of miRNAs and Profiling of ROS Metabolism in Response to Saline–Alkali Stress in Wheat (Triticum aestivum L.)

Saline-alkali stress is one of the important abiotic stresses, which affect plant growth and development. However, the understanding of miRNA pathways in different saline-alkali stress is still limited. In order to better understand the salt-alkali stress response mechanism of wheat, we analyzed miRNA transcription levels in two wheat varieties differing in saline-alkali tolerance (Qingmai 6, QM, tolerant; Meisheng 0308, MS, sensitive) under mixed saline-alkali stress (150 mmol·L¹ and 300 mmol·L¹) for 7 days. High-throughput sequencing identified 11,368 miRNAs (106 conserved, 11,262 non-conserved), among which four miRNAs (miR9653b, miR5384-3p, miR9777, and miR531) exhibited a consistent expression trend across both varieties and all stress concentrations. Additionally, a potential miRNA-mediated regulatory network (including miR408 and miR1135) was predicted to regulate reactive oxygen species (ROS) metabolism via cytochrome P450, plant hormone signal transduction, and MAPK pathways. Saline-alkali-tolerant and sensitive wheat cultivars exhibited distinct miRNA expression patterns under stress. QM maintained higher contents of non-enzymatic antioxidants (ascorbic acid, AsA; reduced glutathione, GSH) and activities of key antioxidant enzymes (ascorbate peroxidase, APX; glutathione reductase, GR), which contributed to balanced ROS homeostasis and enhanced saline-alkali tolerance.