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.

DNA binding proteins with one finger (Dof) transcription factors are essential for seed development and defence against various biotic and abiotic stresses in plants. Genomic analysis of Dof has not been determined yet in pitaya (Selenicereus undatus). In this study, we have identified 26 Dof gene family members, renamed as HuDof-1 to HuDof-26, and clustered them into seven subfamilies based on conserved motifs, domains, and phylogenetic analysis. The gene pairs of Dof family members were duplicated by segmental duplications that faced purifying selection, as indicated by the Ka/Ks ratio values. Promoter regions of HuDof genes contain many cis-acting elements related to phytohormones including abscisic acid, jasmonic acid, gibberellin, temperature, and light. We exposed pitaya plants to different environmental stresses and examined melatonin’s influence on Dof gene expression levels. Signifcant expression of HuDof-2 and HuDof-6 were observed in different developmental stages of flower buds, flowers, pericarp, and pulp. Pitaya plants were subjected to abiotic stresses, and transcriptome analysis was carried out to identify the role of Dof gene family members. RNA-sequencing data and reverse transcription quantitative PCR-based expression analysis revealed three putative candidate genes (HuDof-1, HuDof-2, and HuDof-8), which might have diverse roles against the abiotic stresses. Our study provides a theoretical foundation for functional analysis through traditional and modern biotechnological tools for pitaya trait improvement.

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