Objective Biological characteristics of the gene family related to heat shock transcription factors (HSFs) crucial in plant responses to high-temperature stress in pitaya were studied.

Methods Bioinformatic tools were utilized to analyze the physicochemical properties, motifs, gene structure, domains, chromosome localization, promoters, and phylogenetic tree of the HSF family in Selenicereus spp. Transcriptome and qPCR were employed to determine the gene expressions under heat stress.

Results Thirteen HSF members were identified from the genome. The encoded HSFs were all unstable proteins. Most members contained only one intron belonging to 4 classes of phylogenetics. The genes in the same branch possessed similar or identical conserved motifs and were randomly distributed in 6 chromosomes. Their promoters contained various elements related to the responses to hormone, stress, and light or plant growth and development regulation. The gene structure consisted of specific domains with temporally and spatially specific expressions. Gene expression analysis showed that the expression of pitaya HSF gene had strong temporal and spatial specificity; among them, only five members were expressed in branches with different expression trends, and the expression of HU05G00210.1 and HU05G01887.1 was significantly elevated at 24 h and 48 h, and the expression of HU02G02398.1 and HU10G01257.1 was not significantly elevated until the high temperature treatment of 48 h, while the expression of HU04G00163.1 did not change significantly, reflecting the response of HSF gene to heat stress.

Conclusion This study identified and validated the involvement of HSF family of pitaya in response to heat stress.