Genome-Wide Analysis of SPL Gene Families Illuminate the Evolution Patterns in Three Rubber-Producing Plants

Transcription factors SQUAMOSA Promoter-binding Protein-like (SPL) play a crucial role in regulating plant response to stress, root development, and flower production. However, analysis of SPL gene families in the three rubber-producing plants Taraxacum kok-saghyz, Hevea brasiliensis, and Eucommia ulmoides, renowned for their natural rubber production, has not yet been conducted. In this study, we utilized reference genomes to perform genome-wide analysis, and obtained new insights on the evolution of SPL gene families in these three rubber-producing plants. Our results revealed the following: (1) T. kok-saghyz, H. brasiliensis, and E. ulmoides harbored 25, 16, and 13 SPL genes, respectively, containing conserved structural domains of SBP. (2) A phylogenetic analysis categorized 90 SPL proteins from 25 TkSPLs, 16 HbSPLs, 13 EuSPLs, 17 AtSPLs, and 19 OsSPLs into eight groups. (3) Analysis of cis-acting elements demonstrated that the promoters of EuSPLs contained a significant number of light response elements, hormone regulatory elements, and stress response elements. (4) Transcriptome data analysis revealed that the EuSPL8 gene had strong expression in bark, as well as TkSPL4 and TkSPL8 exhibit high expression levels specifically in roots and latex. This study provides valuable insights into the biological functions of the SPL gene family in the three rubber plants and might serve as a reference for identifying efficient genes.