Comprehensive characterization of SBP genes revealed their role under multifactorial stress combinations in dragon fruit (Selenicereus undatus L.)

The SQUAMOSA PROMOTER BINDING PROTEIN (SBP) gene family is essential for plant growth and development. However, little is known about the SBP gene family in pitaya (Selenicereus undatus L.); a fruit crop cultivated in tropical climates, severely affected by abiotic stress factors. These stresses produce excessive reactive oxygen species (ROS), affecting pitaya growth and development. In this study, we identified 17 SBP genes in the pitaya genome (HuSBP) and classified them into seven distinct clusters based on their phylogeny. The HuSBP genes exhibited a conserved intron-exon structure and motif domain organization. These SBP genes were differentially expressed in 15 developmental stages of flower (F), flower buds (FB), pericarp (PeriC), and pulp. In addition, specific HuSBP genes exhibited higher expression under single-factor, double-factor, and multifactorial stresses, revealing their diverse role in the growth and development of pitaya. Exogenous application of melatonin with known antioxidant and stress-protective properties, was also applied. The expression pattern of RNASeq data was validated by RT-qPCR analysis. Based on genome-wide results and transcriptome-based data under multifactorial stresses, we predicted six putative candidate genes (HuSBP2/3/7/10/14/15) that might play diverse roles in pitaya growth and development. These results provide valuable insights into the role of HuSBP genes in pitaya stress tolerance and could be used to develop innovative strategies to create resilient and adaptable pitaya genotypes using conventional breeding and modern biotechnological tools.