Fire blight, caused by Erwinia amylovora, is a devastating bacterial disease threatening apple, pear, and other Rosaceae species. In our prior study, transcriptome analysis identified a fire blight-resistant variety, Duli (Pyrus betulifolia Bunge), and highlighted the PR1 gene as a key resistance factor. Using Duli’s genomic data, we systematically identified and characterized the Pb-PR-1 gene family through bioinformatics analysis. A total of 31 Pb-PR-1 genes were found, encoding proteins of 123–341 amino acids. Phylogenetic analysis grouped these genes into four subfamilies, with 27 genes distributed across seven chromosomes, all contain a conserved CAP superfamily domain. Their promoter regions were enriched in hormone and stress-responsive elements. After inoculation with E. amylovora, susceptible Duli showed lesion development by day 2, with rapid disease progression, while resistant plants exhibited slower disease advancement and smaller lesions. Enzyme activity assays revealed that in resistant plants, PPO (polyphenol oxidase) and CAT (catalase) activities peaked on day 6, showing a 2.4-fold and 3.81-fold increase compared to susceptible Duli. At the same time, MDA (malondialdehyde) content decreased by 16.6%. The activities of SOD (superoxide dismutase) and PAL (phenylalanine ammonia-lyase) peaked on day 4, with increments of 34.32% and 47.1% over susceptible Duli. qRT-PCR showed significant differences in Pb-PR-1 gene family expression between resistant and susceptible plants post-inoculation. Notably, Pb-PR-1-11, Pb-PR-1-21, and Pb-PR-1-26 expression increased with infection duration, aligning with PPO and CAT activity trends. Other genes showed high early infection expression but declined by day 6. Pb-PR-1-3, Pb-PR-1-6, Pb-PR-1-8, Pb-PR-1-16, and Pb-PR-1-30 were upregulated 13.17-fold on average by day 2. In summary, the Pb-PR-1 family exhibited elevated expression during early infection and enhanced defense-related enzyme activities, improving plant resistance. This study provides a foundation for understanding the PR-1 family’s role in Duli and advancing fire blight resistance in Pyrus species.

The fw2.2 (fruit weight 2.2) gene negatively regulates cell division and significantly influences fruit size, but its regulatory mechanisms in pears remain unclear. Here, we investigated how pear FWL (fw2.2-like) genes control cell division using Duli pear, Korla fragrant pear, and Yali pear. During the cell division phase, fluorescence in situ hybridization (FISH) revealed stronger expression of FWL1 and FWL5 in smaller fruits compared to larger ones, with both genes localized in the core and flesh tissues. Gene silencing experiments demonstrated that silencing of FWL5 leads to a significant increase in the number of cells, with a concomitant enlargement of the fruit. Yeast two-hybrid screening identified 147 proteins interacting with FWL5, showing substantial overlap with FWL1 interactors. Key candidates included metallothionein-like protein (MT) and Ole-e-1, with the latter displaying a positive correlation with fruit size during cell division. Bimolecular fluorescence complementation (BiFC) confirmed direct interactions between Ole-e-1 and both FWL1/FWL5. Functional analysis indicated the Ole-e-1 gene family has diverse roles in pear development. We propose that Ole-e-1 interacts with FWL genes to modulate cell division, thereby determining final fruit size. This study uncovers a novel regulatory axis linking cell cycle control and fruit size in pears.