Context. Heat shock proteins play a vital role in cellular homeostasis by protecting proteins against various environmental stresses, which facilitates the survival of plants under unfavourable conditions.

Aims. We aimed to provide the first comprehensive genomic and expression analysis of the HSP70 gene family in betel palm (Areca catechu) to elucidate its role in heat stress response.

Methods. Genomic analysis revealed 34 putative HSP70 genes distributed across 13 chromosomes. These were renamed AcatHSP70 and classified into five subfamilies (A–E) based on phylogenetic analysis. These genes are mostly localised in the chloroplast, cytoplasm, and nucleus. Gene ontology revealed that these genes are mostly involved in heat stress. The gene duplication events of HSP70 genes involved only segmental duplications. We subjected betel palm seedlings (2 years old) to heat stress under controlled conditions for 30 days at high, low, and room temperatures for expression analyses of HSP70 genes.

Key results. Expression analysis revealed eight putative candidate genes (AcatHSP70-3, AcatHSP70-13, AcatHSP70-22, AcatHSP70-19, AcatHSP70-21, AcatHSP70-24, AcatHSP70-25, and AcatHSP70-26) that showed significantly higher expression under high-temperature stress. AcatHSP70-5 showed higher expression under low-temperature treatment, and AcatHSP70-16 was responsive at room temperature treatment.

Conclusion. We conclude that the majority of AcatHSP70 genes play a crucial role under thermal stress conditions, and respond to high-temperature stress as shown by the quantitative reverse transcription polymerase chain reaction analysis.

Implications. This comprehensive characterisation of the HSP70 gene family provides novel insights into the thermal protection mechanisms of betel palms in changing climates.