Changes Of Coloured And Aromatic Compounds Of Honey Peach Peel And Related Proteomics Studies During Development And Postharvest

Honey peach[Prunus persica(L.)Batsch]is a most favorite fruit of consumers in China because of its attractive color,rich juice content,abundant antioxidants,delicious sweet flavor,and abundant acid and aromatic compounds,it has an important position in fresh fruit market.Peel is the most important and intuitive part of the fruit selected by consumers,especially the color and aroma of the peel are decisive for consumers to purchase fruits.Honey peach fruits(Prunus persica cv.Hujingmilu)were obtained from the peach orchard of Shanghai Academy Agriculture and Science in Pudong(Shanghai,China),to study changes in the color,aroma,sugar and acid of the pericarp,to investigate the key coloured compounds(anthocyanins,carotenoids...etc)and the key proteins associated to their synthesis or degradation of peach fruit peel using iTRAQ techniques,to investigate the changes in aromatic compounds and protein profiles of peach fruit peel using GC-MS and iTRAQ techniques at different peach developmental stages and during the postharvest period,to investigate the effect of shorten bagging period on the changes in color and protein profiles of peach fruit peel using iTRAQ techniques and elucidate the mechanism of bagging to control the change of pericarp characteristics.Honey peach fruits were harvested at 50,70,90,95,100,and 105 days after flowering(DAF),An additional group of 180 fruits was harvested at 105 DAF and divided into three groups stored at room temperature(20-25?)with relative humidity of 80-85%for 3 days(until 108 DAF).All fruits from each sample group were measured individually for single fruit weight,vertical length,horizontal diameter,sugar and acids contents,coloured and aromatic compounds contents.The key proteins associated to coloured and aromatic compounds synthesis or degradation of peach fruit peel were investigated using iTRAQ techniques at 90DAF,95DAF,105DAF and 108 DAF compared to 50 DAF respectively.The main findings are as follows:1?There was a rapid growing stage from 50 to 90 DAF.After 50 DAF,the sucrose,fructose and glucose contents increased,but malic acid and quininic content decreased significantly,it was the critical period for fruit quality formation;the sucrose content increased and malic acid decreased continuously from 100 to 105 DAF,it was the period for fruit flavor improvement;The malic acid content increased significantly from 105 to 108 DAF,it was the period for quality deterioration.Chlorophyll a,chlorophyll b,carotenoid,zeaxanthin and phytoene content increased,but anthocyanin content was near to zero from 50 DAF to 70 DAF,the increase of anthocyanin content was accompanied the decrease of chlorophyll and carotenoid contents from 75DAF to 105 DAF,the increase of chlorophyll a content was accompanied the decrease of chlorophyll b and anthocyanin contents,but the carotenoid,zeaxanthin and phytoene contents were stable from 105 DAF to 108 DAR.GC-MS revealed 163 volatile compounds,among them,116 compounds have a matching degree of 70(percentile),and the information is relatively reliable and accurate,and 18 of them were aroma-related.The cis-2-hexene-l-alcohol and hexaldehyde were regulated by fruit growth,Trans-?-ionone was regulated by fruit senescence,1-hexyl alcohol,cis-3-hexenol,linalool,ethyl acetate,hexyl acetate,cis-3-hexanolactone,?-hexalactone,?-decalactone,and ?-decanolactone were regulated by fruit growth and senescence.The content of sucrose,fructose and glucose in peach fruit was positively correlated with anthocyanin content of pericarp,the content of malic acid and quinine acid content in fruit pulp was significantly negatively correlated with anthocyanin content in pericarp,the content of sucrose,fructose and glucose in pulp was significantly negatively correlated with chlorophyll and carotenoid content in pericarp,the content of malic acid and quinine acid in pulp was positively correlated with chlorophyll and carotenoid content of pericarp.The characteristic aromatic compounds of peach had high correlation with the internal quality of fruit are hexanal,ethyl acetate and gamma-hexalactone,respectively.2?Peel color was regulated by light-harvesting complex chlorophy a/b binding(LHCAB)pathway,chlorophyll degradation pathways,carotenoid metabolism pathways and anthocyanin metabolism pathways.The iTRAQ technique identified 1848 differential expression proteins,and 842 of these were related to biological processes.And between them 58 were related to color and energy transfer,of which 25 were associated with color compound metabolism and 33 with energy transfer.During the development of peach fruit,LHCAB and protochlorophyllide reductase(POR),which had complex ring interactions,are the key functional proteins for regulating chlorophyll metabolism.Chalcone synthase(CHS)and anthocyanidin reductase(ANR)protein interactions,glycosyltransferase(UFGT)and anthocyanidin 3-O-glucosyltransferase(3GT)alone regulate the metabolic process of anthocyanins together.Mg-protoporphyrin IX chelatase and pheophorbide a oxygenase(PAO)are the key functional proteins for regulating chlorophyll metabolism after harvesting.Phytoene synthase(PSY)was the core protein and had linear interactions with beta-carotene 3-hydroxylase,carotenoid cleavage dioxygenase(CCD)and xanthoxin dehydrogenase,which are the key functional proteins for regulating carotenoid metabolism during the development and during the postharvest.LHCAB,POR,PSY1,CCD,Mg-protoporphyrin IX chelatase and PAO which have complex interaction with each other are key functional proteins for regulating coloured compounds of peach peel,of which LHCAB6?PSY?CHS and Mg-protoporphyrin IX chelatase are the key proteins for connecting four metabolic pathways.3?There were 100 differential expression proteins of the total 1848 were with aromatic compound metabolism and energy transfer.The fatty acid metabolism was the primary pathway for aromatic compound formation in peach peel,allene oxide cyclase(AOC),hydroperoxide dehydratase(AOS),lipoxygenase(LOX),and 12-oxophytodienoic acid reductase(OPR)were the key functional proteins,which had cyclic protein-protein interactions and induced fatty acid,lactones,and esters together during peach fruit ripening.The up-regulated linoleate 9(S)-lipoxygenase plays an important role in the increase of hexanal and benzaldehyde content during ripening.The activity of phosphoglycerate mutase,glyceraldehyde 3-phosphate dehydrogenase,and inorganic pyrophosphatase regulated the terpenoids production for linalool through the 3-phosphoglyceric acid/pyruvic acid pathway but not the mevalonic acid pathway.Caffeoyl-CoA-O-methyltransferase had linear interactions with 4-coumarate-CoA ligase and 3-hydroxyisobutyryl-CoA hydrolase,and it might be the critical pathway of aromatic compounds during the development of peach fruit.4?Setting the following two treatments,treatment ?(shorten bagging period treatment):Bags of fruit was removed for coloring after 90 after flowering(DAF);treatment ?(bagging treatment):Fruits were covered with bags until 105 DAF.Shortening the bagging duration period could improve the red color and anthocyanin content of peach peel and maintain the stability of anthocyanins,but reduce peel brightness and chlorophyll content.Compared to treatment ?,the expression of LHCAB protein and other related proteins in peach peel were not down-regulated in treatment ? during the development but the chlorophyll content was lower of treatment ? than treatment ?;It could promote chlorophyll degradation by up-regulating PPR and PAO and not down-regulating LHCAB proteins at 108 DAF.Shortening bagging duration could increase the anthocyanin content,however,the expression of ANS,ANR,3GT,and CHS was unaffected at 105 DAF,which could inhibit the degradation of anthocyanin by up-regulating the expression of CHS at 108 DAF.Shortening bagging duration could inhibit the accumulation of carotenoid in peach peel by down-regulating the expression of PSY from 105-108 DAF,and decrease the carotenoid content by up-regulating CCD 4 at 108 DAF.Shortening the bagging duration period could affect this by regulating PAO,3GT,CHS and CCD 4.