Adaptive Traits and Molecular Mechanisms of Rhododendron Species in Changbai Mountains’ Alpine Tundra: A Phenotype–Transcriptome Study

Alpine tundra's harsh conditions challenge plants, but <i>Rhododendron</i>'s adaptive mechanisms remain unclear. This study explored phenotypic/transcriptomic adaptations of three <i>Rhododendron</i> species (<i>R. aureum</i>, <i>R. lapponicum</i>, <i>R. redowskianum</i>) in Changbai Mountains' tundra vs. timberline. Mature leaves were sampled for leaf length and leaf width measurement and RNA-seq. Results showed leaf width (not leaf length uniformly) reduced in tundra across all species. RNA-seq identified 2399-5716 DEGs per species; plant dwarfism DEGs (e.g., DELLA, EDS1) were up-regulated. Shared DEGs were enriched in carbon/nitrogen metabolism and stress response; IPUT1 (DUH022406.1) and PGT1 (DUH001929.1) were consistently down-regulated (linked to dwarfism). Species-specific responses included <i>R. aureum</i>'s light adaptation, <i>R. lapponicum</i>'s freezing/hypoxia response, and <i>R. redowskianum</i>'s sugar/UV/microbial regulation. <i>Rhododendron</i> adapts to tundra via leaf width adjustment, metabolic optimization, and IPUT1/PGT1-mediated dwarfism, with conserved core mechanisms and species specialization, supporting climate change response predictions and conservation.