Genome-Wide Analysis of the SABATH Family in Rosa chinensis and Functional Analysis of RcSABATH20 in Black Spot Disease

The plant SABATH family of methyltransferases has important biological functions by methylating hormones and signaling molecules and other metabolites. In this study, we identified 47 RcSABATH genes from the Rosa chinensis genome, the majority of which are located in the cytoplasm. Following this, a comprehensive analysis was conducted on SABATH genes of Prunus persica, Malus domestica "Golden," Prunus avium, and Prunus dulcis, which included phylogenetic and chromosome duplication analysis, gene structure examination, and functional domain and conserved motif analysis. The results revealed that SABATH family members across these five species were divided into three categories, with Group I containing the highest number of family members and Group III the lowest. Gene clusters were observed on the chromosomes of each species, indicating the occurrence of tandem repeat events during the evolutionary process of SABATH members. Furthermore, the analysis of gene structure, conserved motif, and conserved domain highlighted the diversity and conservation among SABATH family members. The transcriptome data of R12-26 and R13-54 infected by Marssonina rosae infection was used to screen 35 RcSABATHs, which were subsequently categorized into three groups (a, b, and c) based on their expression characteristics. Notably, Group c consisted of members that were induced and up-regulated during the late stage of R12-26 infection. Among the identified genes, RcSABATH20 drew our attention due to its involvement in various hormone and abiotic stress regulation pathways. To ascertain the function of RcSABATH20, we conducted experiments by treating the leaves of the resistant line R13-54 and susceptible line R12-26 with SA and the SA synthesis inhibitor AIP. The outcomes revealed a direct correlation between the expression of RcSABATH20 and resistance to rose black spots. Furthermore, it was observed that SA could enhance the expression of RcSABATH20, thereby contributing to the resistance against rose black spots. These findings establish a theoretical foundation for exploring the molecular mechanisms underlying SABATH resistance to rose black spots.