Quantifying redox signalling regulatory transcriptional dynamics in Nardostachys jatamansi under abiotic stress...

Understanding the responses of Himalayan medicinal plants to multifactorial stresses is crucial in the face of increasing environmental challenges, primarily characterised by frequent temperature and water availability fluctuations. The present study investigates the physiological, biochemical, and transcript variations in the critically endangered Himalayan medicinal plant Nardostachys jatamansi subjected to cold (15 °C and 10 °C for 30 days), drought (6 % PEG for 30 days), and heat stress (30 °C for 24 h). The primary impact of stress was observed through reduced plant biomass and chlorophyll fluorescence. The effects of abiotic stresses were also evident in the modulation of electrolyte leakage, MDA content and H₂O₂ accumulation. Accumulation of reactive oxygen species was confirmed through DAB and NBT staining, alongside increased DPPH and ABTS radical scavenging activity. Differential expression profiling of the RBOH family transcripts further substantiated the production of ROS. Enhanced enzymatic and non-enzymatic activities were observed under each abiotic stress condition. Additionally, genes specific to the regulatory mevalonate (MVA) pathway (TPS9; HMGR) and the methylerythritol phosphate (MEP) pathway (DXS1; DXR) were found to be differentially regulated. Moreover, differential expression profiling of abiotic stress signalling regulatory transcripts CRLK1, CRLK2, CaM6 and ICE1 was also discovered. These findings provide valuable insights into the physiological and biochemical profiling of N. jatamansi in response to extreme environmental conditions, significantly aiding our understanding of the adaptation strategies of alpine vegetation for their conservation.