Key proteins associated to coloured compounds of peach peel using iTRAQ proteomic techniques during development and postharvest

This study aimed to investigate the key coloured compounds (anthocyanins, carotenoids…etc) and the key proteins associated to their synthesis or degradation of peach fruit peel (Prunus persica 'Hujingmilu') using iTRAQ techniques at different peach developmental stages and during the postharvest period. Peach fruits were collected 50 d, 90 d, 95 d, 100 d, and 105 day after flowering, as well as fruits being stored for 3 days after picking at 105 days after flowering. The key coloured compounds of 'Hujingmilu 'honey peach peel is composed of, among others, chlorophyll, anthocyanin, carotenoids, zeaxanthin, and lycopene. Peel color was regulated by chlorophyll degradation pathways, carotenoid metabolism pathways, and anthocyanin metabolism pathways, the iTRAQ technique identified 1848 unique proteins, of which 842 were related to biological processes, and 25 were related to color and 33 were related to energy transfer during fruit development and postharvest. During the development of peach fruit, light-harvesting complex chlorophyll a/b binding protein (CAB) and protochlorophyllide reductase(POR) are the key functional proteins for regulating chlorophyll metabolism, anthocyanidin 3-O-glucosyltransferase (3 G T) and UFGT are the key functional proteins for regulating anthocyanidin metabolism, PSY, zeta-carotene desaturase (ZCD) and carotenoid cleavage dioxygenase (CCD) are the key functional proteins for regulating carotenoid metabolism during the development and the postharvest period of peach fruit. Mg-protoporphyrin IX chelatase and pheophorbide a oxygenase (PAO) are the key functional proteins for regulating chlorophyll metabolism during postharvest. The key proteins were regulated a little earlier or accompany with the increase or decrease of peach peel coloured compounds. These results provide further understanding of the key coloured compounds of peach peel color, key proteins associated to coloured compounds, and reveal how the differential proteins take part in coloured compound metabolism pathway during fruit development and postharvest.