硫化氢通过PpMYB73抑制PpPPO1转录调控桃果实冷害褐变的分子机制

《Postharvest Biology and Technology》：Transcription factor PpMYB73 inhibits PpPPO1 transcription and flesh browning in hydrogen sulfide-mitigated chilling injury of peach fruit

本研究揭示了硫化氢(H2S)缓解桃果实冷害褐变的新机制。发现转录抑制因子PpMYB73通过直接抑制多酚氧化酶基因PpPPO1的转录，促进绿原酸(CGA)积累并抑制醌类物质产生，从而减轻褐变。该研究为水果采后冷害控制提供了新的理论依据和靶点。

　　

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Materials and treatments

'Hujingmilu' peaches (Prunus persica) were collected at the commercial maturity stage (firmness approximately 35 ± 2 N) from the Jiangsu Academy of Agricultural Sciences, Nanjing, China. Peach fruit were selected based on uniform maturity, size, and absence of mechanical damage. A total of 300 fruit were randomly divided into two groups, with 150 fruit per group (each group containing three replicates of 50 fruit). All selected peaches were fumigated with 20 μL L^?1 H₂S or ultrapure water.

Identification and bioinformatics analysis of PPO genes in peach

Five PPO genes were identified in peach using HMMER and BLASTp, and were designated PpPPO1–5 according to their locations on chromosome 4 (Table S2). The predicted PpPPO proteins all shared five conserved motifs and typical PPO domains PPO1_DWL, PPO1_KFDV, and Tyrosinase (Fig. 1A?D and Fig. S1A), which were correlated with oxidation and reduction activities of PPO enzymes (Martinez-Garcia et al., 2016). Five PpPPO genes contained non-coding regions at both the 3′ and 5′ terminals but no introns.

Discussion

CI-induced deteriorating quality, particularly flesh browning, remains a major limiting factor for the fruit's cold chain transport and marketing. Flesh browning represents the primary CI symptom in cold-stored ‘Hujingmilu’ peach fruit, significantly compromising its commercial value (Zhao et al., 2023). Enzymatic browning in fruit is a complex physiological process initiated by cellular compartmentalization disruption, leading to catalyzed oxidation of phenolic compounds into quinones (Yuan et al., 2025).

Conclusions

We identified the H?S-responsive R2R3-MYB TF PpMYB73, conferring cold tolerance in peach fruit by suppressing phenolic oxidation (Fig. 8). PpMYB73 acted as a transcription repressor of PpPPO1 expression, promoted CGA accumulation, thereby inhibiting soluble quinones production and flesh browning in cold-stored peach fruit. H?S treatment upregulated PpMYB73 expression and enhanced its suppression of PpPPO1, further preventing flesh browning in peach fruit. Our findings provided a molecular basis for alleviating CI in peach fruit.