Time-Resolved Transcriptomics Reveals Coordinated ROS, SOS and ABA Signaling in White Birch
Salt stress severely limits plant growth, particularly in woody species. In this study, a time-course transcriptomic analysis (0–24 h NaCl treatment) revealed a clear time-dependent transcriptional reprogramming pattern in Betula platyphylla, characterized by rapid early activation followed by gradual stabilization. The response can be divided into three phases: early stress perception and signaling (1–3 h), mid-stage metabolic and hormonal reprogramming (5–9 h), and late-stage homeostasis and physiological adaptation (12–24 h). Early responses are dominated by signal transduction, the middle phase by metabolic reorganization and enhanced translation, and the late phase by redox and cellular homeostasis. Compared to the limited role of the Dehydration-Responsive Element-Binding protein (DREB) pathway, Abscisic acid (ABA) and Jasmonic acid (JA) signaling appear to play more central regulatory roles. Further analyses revealed the coordinated temporal activation of Reactive oxygen species (ROS), Salt Overly Sensitive (SOS), and ABA pathways: ROS shows an early burst followed by antioxidant activation; the SOS pathway regulates ion homeostasis via the Calcineurin B-like protein (CBL)-CBL-interacting protein kinase (CIPK) module; and ABA signaling progresses from biosynthesis to downstream transcriptional regulation. Protein interaction network analysis further identifies ABA signaling as a central hub integrating Ca2+ signaling, ROS metabolism, and ion transport. Overall, B. platyphylla responds to salt stress through a temporally coordinated regulatory network, providing new molecular insights into salt tolerance mechanisms in woody plants.