Physiological and Transcriptomic Responses of Asterothamnus centraliasiaticus Leaves to Drought Stress

Asterothamnus centraliasiaticus is a key species within the desert ecosystems of the Qinghai–Tibet Plateau. To elucidate the physiological responses and underlying molecular mechanisms of drought tolerance in A. centraliasiaticus, this study employed high-throughput RNA sequencing of leaf tissues to identify key pathways and drought resistance-related genes associated with adaptation to water deficit conditions. Physiological analyses revealed that drought stress significantly enhanced the activities of antioxidant enzymes, increased the accumulation of osmotic adjustment substances and membrane damage indicators, and elevated relative electrical conductivity in leaves. In contrast, total ROS levels were significantly reduced under drought stress, indicating effective activation of antioxidant defense systems. Transcriptome analysis identified 15,010 differentially expressed genes (DEGs) in response to drought stress. GO and KEGG enrichment analyses revealed that these DEGs were predominantly involved in phenylpropanoid biosynthesis, plant hormone signal transduction, and zeatin biosynthesis pathways, which are closely associated with stress perception, signal transduction, and adaptive metabolic regulation. Moreover, qPCR validation of 15 randomly selected genes corroborated the RNA-seq results, confirming the reliability of the transcriptomic data. Collectively, these findings provide a valuable molecular framework for understanding drought response pathways and identifying drought resistance genes in A. centraliasiaticus, thereby offering theoretical support for future studies on xerophytic plant adaptation and molecular breeding for drought tolerance.