Comprehensive Analysis of Malate Accumulation in Peaches in Response to Cold Stress Based on Transcriptomics.

Malate is the predominant organic acid in peach, contributing significantly to fruit sourness and overall organoleptic quality. However, comprehensive understanding of the molecular mechanisms underlying malate accumulation in response to different storage conditions remains limited. In this study, "Hujingmilu" peach was subjected to room temperature (RT, 25°C), low temperature (LT, 4°C), and LT followed by shelf life (LT-SL, 25°C) treatments to investigate transcriptional regulation mechanisms underlying malate accumulation, with emphasis on biosynthesis, vacuolar storage, and transcription factor regulation. Results demonstrated that LT storage delayed the decline in fruit firmness and maintained higher malate content compared to RT and LT-SL. Transcriptomic profiling indicated that the expression patterns of malate biosynthetic genes (PpPEPC1/2, PpNAD-MDH1/2, PpNADP-ME1) showed limited alignment with malate accumulation. In contrast, genes implicated in proton pump and malate transporter, such as PpAtpvA1/2/3/4/5, PpVp2, and PptDT1, were significantly upregulated under LT conditions, consistent with the observed malate accumulation. Furthermore, LT storage repressed the malate transcriptional repressor PpTST1 while inducing the candidate regulatory gene PpMYB62. These findings provided a comprehensive molecular framework for understanding malate modulation under varying storage conditions.