Abstract
Plant-specific transcription factors known as SQUAMOSA promoter binding protein-like (SPL) genes are essential for development, growth, and abiotic stress responses. While the SPL gene family has been extensively studied in various plant species, a systematic characterization in Zanthoxylum bungeanum (Zb) is lacking. This study used transcriptomic and bioinformatics data to conduct a thorough genomic identification and expression investigation of the ZbSPL gene family. Eight subfamilies including 73 ZbSPL members were identified, most of which are predicted to be localized in the nucleus. Ka/Ks ratio analysis indicates that most ZbSPL genes have undergone purifying selection. According to evolutionary research, segmental duplication is a major factor in the amplification of the ZbSPL gene family. Gene structures, conserved motifs, and domains were found to be highly conserved among paralogs. Cis-element research revealed that ZbSPLs may be implicated in hormone and abiotic stress responses. Codon usage pattern analysis showed that the ZbSPL gene family was more inclined to A/T base endings; the higher the A/T content, the stronger the preference of the codons; and the use pattern was mainly affected by natural selection. Additionally, 36 ZbSPLs were found to be potential targets of miR156. RNA-seq demonstrated that SPL genes in Zb are differentially expressed in response to distinct abiotic stressors. Two ZbSPL genes (ZbSPL10 and ZbSPL17) were implicated in the response to salt stress, while four ZbSPL genes (ZbSPL06, ZbSPL43, ZbSPL60, and ZbSPL61) showed response to drought stress, based on a qRT-PCR investigation of the ZbSPL genes under various abiotic stress conditions. This study will help us gain a deeper understanding of the functions of ZbSPLs and lay a genetic foundation for future breeding of high-quality, highly abiotic resistant varieties of Z. bungeanum.