Functional characterisation of Dof gene family and expression analysis under abiotic stresses and melatonin-mediated tolerance in pitaya (Selenicereus undatus)

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 K-a/K-s 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.