High-Quality Genome Assembly and Transcriptome of Rhododendron platypodum Provide Insights into Its Evolution and Heat Stress Response.

R. platypodum (Rhododendron platypodum) is an endangered alpine species with a highly restricted distribution in the southwestern region of China, which possesses significant ornamental and horticultural value. In this study, the high-quality genome assembly of R. platypodum at the chromosomal level is reported. The total genome size was determined to be 642.25 Mb, with a contig N50 of 25.64 Mb, and it contains 36,522 predicted genes. Comparative genomic analysis between R. platypodum and other species revealed the expansion of gene families, such as those related to transition metal ion binding and sodium ion transport, as well as the contraction of gene families involved in the recognition of pollen and pollen-pistil interaction. These findings might explain the adaptation of R. platypodum to rocky habitats and contribute to its endangered status. Furthermore, a heat stress experiment was conducted on R. platypodum, followed by transcriptome sequencing and physiological co-analysis to construct a co-expression network. This analysis identified the candidate gene TAR1-A and other transcription factors exhibiting differential expression under heat stress. The whole-genome sequencing, transcriptome analysis, and physiological co-analysis of R. platypodum provide valuable resources for its conservation and offer insights into its mechanisms of heat stress.