Genome-wide identification of calcium-dependent protein kinase (CDPK) family genes in pear (Pyrus bretschneideri) and functional characterization of PbrCDPK8 in black spot tolerance

Calcium-dependent protein kinases (CDPKs) are key regulators of plant stress responses. Although their function is characterized in model species, their roles in pear ( Pyrus bretschneideri ) remain largely unexplored. This comprehensive study identified 40 PbrCDPK genes in the Chinese white pear genome and classified them into four conserved subfamilies. The expansion of this gene family was mainly driven by segmental and dispersed duplications. Promoter cis -element profiling identified multiple stress-responsive motifs associated with hormone signaling, biotic challenges, and abiotic stressors. Transcriptomics and quantitative reverse transcription–polymerase chain reaction revealed that PbrCDPK8 , PbrCDPK23 , PbrCDPK29 , and PbrCDPK36 were significantly upregulated following infection with Alternaria alternata . Subcellular localization experiments confirmed the plasma membrane targeting of PbrCDPK8 . Functional analysis demonstrated that PbrCDPK8 -silenced pear seedlings at 42 days of age exhibited compromised resistance to black spot disease, resulting in increased H 2 O 2 accumulation and peroxidase (POD) activities, and reduced β -1,3-glucanase ( β -1,3-GA) and phenylalanine ammonia-lyase (PAL) activities. Conversely, PbrCDPK8 -overexpressing pear callus displayed enhanced disease resistance, marked by decreased H 2 O 2 levels and POD activities and increased PAL activities. This study identified PbrCDPK8 as a positive regulator of black spot resistance, suggesting that PbrCDPK family members may play an essential role in the disease resistance mechanisms of pear.