Whole-genome Identification of the PP2C Gene Family in citrus and its response to Abiotic Stresses

Background In plants, Protein Phosphatase 2C (PP2C) functions as a key protease in responses to various environmental stresses. Although the PP2C gene family has been extensively characterized in plants such as Arabidopsis thaliana and Oryza sativa , its structural features and stress-responsive patterns remain rarely unexplored in citrus. This study aims to address this gap by conducting a genome-wide identification and functional characterization of PP2C genes in citrus, with a focus on their expression profiles under abiotic stress conditions. Results A comprehensive genome-wide analysis was performed in citrtus, and a total of 47 PP2C genes ( CsPP2C1 – CsPP2C47 ) were identified. All CsPP2C members possess conserved PP2C catalytic domains. Physicochemical characterization revealed that CsPP2C proteins exhibited a molecular weight range of 20.03–124.36 kDa, with the majority being acidic (pI < 7), inherently unstable (instability index > 40), and hydrophilic (grand average of hydropathicity < 0). Phylogenetic analysis clustered them into 12 subgroups consistent with model species, indicating functional conservation of the gene family. These genes are unevenly distributed across 9 citrus chromosomes, and promoter cis-acting element analysis uncovered enrichment of stress-related motifs (MBS, LTR) and hormone-responsive elements (ABRE). Quantitative real-time PCR analysis revealed distinct expression patterns of CsPP2Cs in response to PEG, low temperature, salt, and hormone treatments at 0, 12, and 24h, suggesting the important roles in citrus growth and development as well as abiotic stresses. Conclusions This study presented a comprehensive characterization of the PP2C gene family in citrus, clarifying its evolutionary relationships, structural diversity, and stress-responsive expression profiles. The findings established a foundational framework for elucidating the molecular mechanisms underlying CsPP2C-mediated stress adaptation, and provided candidate genes for molecular breeding of stress-resilient citrus varieties.