Genome-wide analysis of WRKY gene family in tree peony (Paeonia suffruticosa) and function of PsWRKY7 in responses to Alternaria alternata

• The WRKY gene family is related to defense responses in plants. • WRKYs positively regulates the resistance of plant to pathogen. • The WRKY gene family can comprehensively analyzed by gene-wide analysis. • The function analysis indicates the potential role of PsWRKYs against A. alternata. The WRKY gene family, is a group of plant-specific transcription factors (TFs) that are involved in a wide range of pathogen attacks and physiological processes in plants. As a main pathogen of black spot, Alternaria alternata greatly reduces the ornamental and economic value of tree peony ( Paeonia suffruticosa ). However, the genome-wide analysis and function of the WRKY gene family are still unknown in tree peony response to A. alternata infection. Herein, we reported a genome-wide analysis of 66 WRKYs in tree peony. They were unevenly distributed across all 5 chromosomes and categorized into three major groups, segmental and tandem duplication events were significant contributors to the evolutionary processes of the WRKY gene family. The presence of diverse cis-regulatory elements within the promoter region revealed WRKYs potential involvement in the growth, development, and stress responses of P. suffruticosa , and most WRKY proteins may participate in abiotic and biotic stresses based on Go and KEGG analysis. Transcript expression levels and relative expression of part WRKYs were significantly up-regulated in the leaf of the tree peony treated with A. alternata , indicating their potentially important roles in pathogen attack. PsWRKY7 in Group IIc was selected for subsequent functional analysis. We found the PsWRKY7 was mainly localized in the nucleus. Furthermore, PsWRKY7 in overexpressing lines of Populus davidiana × P. bolleana enhanced resistance to A. alternata . Taken together, our findings provide valuable insights into P. suffruticosa WRKY gene family and its members’ potential functions to A. alternata infection.