Abstract: The aim of this study was to elucidate the molecular mechanisms ofFreesia hybridain responding to high-temperature stress and to promote the innovation of heat-tolerant germplasm,F. hybrida‘Red River’ was used as the experimental material. Physiological parameters were measured under heat stress at 40 ℃ for varying durations (3, 6, 9 and 12 hours). RNA-seq was conducted on seedlings exposed to 40 ℃ for 12 hours (stress group) compared to those maintained at 20 ℃ for 12 hours (control group). Differentially expressed genes (DEGs) were then identified and analyzed using GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment. Compared to that of the control group, a total of 2961 DEGs were identified after 12 hours of treatment at 40 ℃, including 1306 up-regulated and 1655 down-regulated genes. The GO analysis revealed that the significantly upregulated DEGs were primarily involved in response to heat, protein folding, protein complex oligomerization, response to reactive oxygen species (ROS), and protein import into the mitochondrial matrix. The KEGG pathway enrichment analysis identified several top-ranked metabolic pathways, such as protein processing in the endoplasmic reticulum, plant hormone signal transduction, phenylpropanoid biosynthesis, flavonoid biosynthesis, and photosynthesis-antenna proteins. Notably, the DEGs were consistent with the observed physiological changes under high-temperature stress. Specifically, 17 heat shock protein (Hsp) genes (out of 59 identified), 4 heat shock transcription factors (HSF) (out of 23), and the CUL3A gene exhibited significant up-regulation during thermal stress. Furthermore, transcription factors such as bZIP44, ERF63, ERF51, and NAC42 collectively formed a thermotolerance regulatory network inF. hybrida. Within the plant hormone signal transduction pathway, 18 DEGs were identified as being involved in the regulation of various phytohormones in response to high-temperature stress.

Key words: Freesia hybrida, transcriptome analysis, high temperature stress, physiological indicators