The PAT Gene Family in Citrus: Genome-Wide Identification and Its Potential Implications for Organic Acid Metabolism

Protein palmitoylation, a key post-translational modification (PTM) regulating protein transport and function, is catalyzed by palmitoyl transferases (PATs). PATs play vital roles in plant growth, development, and stress responses, yet their characterization in citrus remains limited. This study identified 23 PAT genes (CitPATs) possessing the conserved DHHC domain in the citrus genome through comprehensive genome-wide analysis. Analysis revealed that most CitPAT proteins are hydrophilic, basic, and stable, with significant variations in sequence length. Gene structure and motif analysis confirmed 10 conserved motifs, with the DHHC domain being the most conserved among all 23 members. The CitPAT genes were unevenly distributed across nine chromosomes and exhibit high evolutionary conservation. Promoter analysis identified numerous cis-acting elements associated with abiotic stress and hormone responses, including basic regulatory elements, light-responsive elements, and stress-responsive elements, with light-responsive elements being predominant. Expression profiling during fruit development revealed distinct correlation patterns with citric acid dynamics: CitPAT6, CitPAT18, and CitPAT23 showed positive correlations with acid accumulation, while CitPAT1, CitPAT10, and CitPAT13 exhibited negative correlations. Further RT-qPCR experiments revealed that CitPAT1 and CitPAT10 consistently demonstrated strong negative correlations with citrate content throughout fruit development. This functional diversification suggests roles in regulating citric acid metabolism. These findings provide novel insights into quality formation in facility-cultivated citrus and establish a foundation for understanding PAT-mediated regulation of fruit development.