Genome wide analysis of the EXP family in Rosa chinensis and negative regulation of black spot disease by RcEXPA8

Expansins constitute a class of proteins instrumental in modulating the laxity and enhancing the flexibility of the cell wall, thereby exerting critical influence on plant growth and development and environmental resistance. This study endeavors to perform bioinformatic analysis on the EXP gene family in Rosa chinensis and investigate the role of RcEXPA8 in response to Marssonina rosae (M. rosae) infection and hormonal signaling pathways. A total of 31 RcEXPs were reported in Rosa chinensis genome, and subjected to phylogenetic and synteny analysis in conjunction with Prunus persica, Malus domestica ‘Golden’, Arabidopsis thaliana and Nicotiana tabacum; followed by synteny, chromosomal localization, structural and motif analysis, as well as cis-regulatory element examination in Rosa chinensis. The EXP gene family was categorized into four subfamilies: EXPA, EXPB, EXLA and EXLB. The highest number of collinear gene pairs were identified between Rosa chinensis and Rosaceae family members Prunus persica and Malus domestica ‘Golden’. Furthermore, and the RcEXP genes were found to be unevenly distributed across seven chromosomes. Ten conserved motifs were found, and the majority RcEXPs exhibited light response elements, plant stress defense elements, and various hormone-associated elements. Subsequent analysis focused on RcEXPA8 elucidated its role in hormonal signaling pathway during M. rosae infection, revealing differential expression patterns in susceptible line R12-26 and resistant line R13-54. Overall, this research provides valuable insights into the Rosa chinensis EXP gene family and its members' responsiveness to black spot disease.