Molecular and biochemical responses to wounding in mesocarp ofripe peach (Prunus persica L. Batsch) fruit

tThe physiological and molecular responses of ripe fruit to wounding were evaluated in two peach (Prunuspersica) varieties (‘Glohaven’, GH, melting and ‘BigTop’, BT, slow melting nectarine) by comparing meso-carp samples from wedges (as in minimal processing) and whole fruit as the control. Slight differencesbetween the two varieties were detected in terms of ethylene production, whereas total phenol andflavonoid concentrations, and PPO and POD enzyme activities showed a general increase in wounded GHbut not in BT. This was associated with the better appearance of the BT wedges at the end of the exper-imental period (72 h). Microarray (genome-wide PEACH3.0) analysis revealed that a total number of2218 genes were differentially expressed (p < 0.01, log2fold change expression ratio >1 or <−1) in GH24 h after wounding compared to the control. This number was much lower (1208) in BT. According tothe enrichment analysis, cell wall, plasma membrane, response to stress, secondary metabolic processes,oxygen binding were the GO categories over-represented among the GH up-regulated genes, whereasplasma membrane and response to endogenous stimulus were the categories over-represented amongthe down-regulated genes. Only 32 genes showed a common expression trend in the two varieties 24 hafter wounding, whereas a total of 512 genes (with highly represented transcription factors), displayedopposite behavior. Quantitative RT-PCR analysis confirmed the microarray data for 18 out of a total of 20genes selected. Specific WRKY, AP2/ERF and HSP20 genes were markedly up-regulated in wounded GH,indicating the activation of regulatory and signaling mechanisms probably related to different hormonecategories. Compared to BT, the expression of specific genes involved in phenylpropanoid and triter-penoid biosynthetic pathways showed a more pronounced induction in GH, highlighting the differencebetween the two peach varieties in terms of molecular responses to wounding in the mesocarp tissue