Abstract

Squamosa promoter binding protein (SBP) plays a vital role in plant growth, development, and responses to abiotic stresses. The genusNotopterygiumis an endangered perennial herbaceous plant mainly distributed in the high-altitude Qinghai–Tibet Plateau and adjacent areas, which possibly occurred the adaptive evolution to the extreme environmental conditions. In this study, we firstly determined the genome-wide structural characteristics, evolutionary history, and expression profiles of theSBPfamily genes inNotopterygiumspecies by using genome, transcriptome, and DNA resequencing data. We have also investigated the response patterns ofSBPsofN. franchetiito the drought and high-temperature stresses. The 21, 18, and 18SBPfamily genes of threeNotopterygiumspecies,N. incisum,N. franchetii, andN. forrestii, were, respectively, identified and classified into eight subfamilies, with four subfamily members regulated by miR156. The structure analysis showed that the members of the sameSBPsubfamily had similar structures and conserved motif composition.Cis-element analysis suggested that thoseSBPgenes may have been essential to the growth and environmental adaptation ofNotopterygium. The expansion of theSBPgene family was mainly caused by the whole genome duplication/segmental duplication and transposable element duplication. Evolutionary analysis showed theSBPgene family experienced severe contraction events and most of the gene copies underwent purification selection. Population genetics analysis based onSBPsvariations suggested that the genusNotopterygiumspecies have obvious genetic structure and interspecific differentiation. RNA-seq and qRT-PCR experiments demonstrated that the expressions ofSBPsgenes inNotopterygiumwere not species-specific, but tissue-specific.NinSBP08andNinSBP10/12may have played the key roles in heat tolerance and drought resistance, respectively. These results provided novel insights into the evolutionary history of theSBPgene family in the endangere