Genetic Responses to Drought and Waterlogging Stresses of Longleaf Speedwell (Pseudolysimachion longifolium)

Climate change necessitates a deeper understanding of plant tolerance mechanisms to dual water stresses. This study investigated the distinct physiological and genetic responses of Longleaf Speedwell (Pseudolysimachion longifolium) to drought and waterlogging using RNA-Seq. Physiological data showed a rapid and comparable reduction in photosynthetic efficiency after one week and a reduction in biomass under both stresses after two weeks. However, transcriptomic analysis revealed fundamentally distinct strategies: Drought induced a massive transcriptional response characterized by the strong upregulation of defense and stress-tolerance pathways and the severe shutdown of growth-related metabolism. In contrast, waterlogging triggered a constrained hypoxic response, prioritizing energy conservation by downregulating synthesis processes and activating ethylene signaling. The reliability of the RNA-Seq data was confirmed by qRT-PCR, which also crucially identified Alcohol dehydrogenase (ADH), Ethylene Responsive Factor (ERF), and Peroxidase (POD) as common candidate genes highly induced under both drought and waterlogging conditions, suggesting a shared genetic module for general water stress tolerance. These findings provide valuable insights into the adaptation mechanisms of non-model plants to complex environmental changes.