The C2H2-GGAT Regulatory Module Fine-Tunes Glutamate Homeostasis to Improve Fruit Flavour and Enhance Disease Resistance in Peach.

Free amino acids (FAAs) play a fundamental role in determining fruit quality and stress adaptation, yet their genetic regulation remains poorly understood. Through an integrated approach combining metabolomic and sensory analyses of 120 peach (Prunus persica) hybrids, we identified glutamate as a key metabolite linking FAA content to umami taste perception. By combining genome-wide association studies (GWAS) with expression quantitative trait locus (eQTL) mapping, we identified PpGGAT1 (glutamate:glyoxylate aminotransferase) and the zinc finger transcription factor PpC2H2-3 as central regulators of glutamate metabolism. Functional characterisation revealed that overexpression of PpGGAT1 led to reduced glutamate levels and diminished umami intensity, whereas PpC2H2-3 transcriptionally suppresses PpGGAT1 to enhance glutamate accumulation. Notably, elevated glutamate levels enhanced resistance to Monilinia fructicola infection, with both genes showing significant expression changes during the progression of brown rot disease. Comparative analysis further indicated that freestone cultivars exhibit superior glutamate accumulation, a trait confirmed across 100 commercial varieties. Our findings reveal a novel regulatory module, PpC2H2-3-PpGGAT1, that coordinately modulates fruit flavour quality and defence responses against pathogens. This study provides mechanistic insights into FAA regulation in fruit crops and identifies actionable molecular targets for the development of varieties with enhanced sensory attributes and disease resistance.