Transcriptome analysis reveals heat stress-responsive genes in octoploid strawberry seedlings and expression pattern analysis of <i>FaHSF</i> gene family under heat stress

Extreme high temperatures severely affect the cultivation of octoploid strawberry seedlings. However, the molecular mechanisms of heat stress response in strawberry seedlings remain unclear. The results demonstrated that when strawberry seedlings were subjected to 40 °C treatment for 6 hours, the proline content and activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) all exhibited significant increases compared to the control group maintained at 25 °C. Consequently, strawberry seedlings exposed to either 25 °C or 40 °C for 6h and 24h were selected for subsequent transcriptomic analysis. A total of 11,526 heat stress-responsive genes were identified. Multiple metabolic pathways associated with heat stress were uncovered by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Sixty-six <i>FaHSF</i> genes were identified in octoploid strawberries, among which <i>FaHSFA2/A3/A7/B1/B2</i> were significantly up-regulated under heat stress according to transcriptomic analysis, and were further validated by quantitative reverse transcription polymerase chain reaction (RT-qPCR) assay, confirming the reliability of the transcriptome data generated in this study. Collectively, these results facilitate the identification of key heat stress resistance genes in octoploid strawberry and offer valuable insights into the mechanisms of heat tolerance, providing candidate targets for the breeding of heat-resistant varieties.