Effect Of Spermidine And D-arginine On Polyamine Metabolism And Ripening Postharvest In Apricot Fruits

Saimaiti apricots are one of the unique varieties of fresh and processed in Xinjiang.The apricot fruit has a short shelf life and easy to softening and metamorphic,resulting in a sharp drop in taste and flavor.As an important amine of polyamines(PAs),spermidine(Spd)can regulate fruits respiration,ethylene release and polyamine metabolism,delay the ripening and senescence of fruits.Semiti apricot was used as the materials,treat with Spd and D-arginine(D-Arg),studied the activity of softening-related enzymes,polyamine metabolism related enzymes activity,Put/Eth,Spd/Eth,and Spm/Eth ratios,transcriptome sequencing and polyamine synthesis related gene expression during storage,analysis of the relationship between polyamine levels and ethylene release,effect of Spd,D-Arg on PAs metabolism of apricots is discussed.The main results are as follows:(1)The green stage Saimaiti apricots at postharvest treated with Spd could effectively maintain fruits firmness,inhibit the activity of PME,PG,Cx,?-Gal,AMS and chlorophyllase,delay the softening of the fruit texture,D-Arg treatment can accelerate the decline of fruit hardness,promote the ripening and senescence of Saimaiti apricots.(2)Spd treatment could enhance the activity of ADC,ODC and SAMDC in Saimaiti apricots,promote the accumulation of Put content and increase the content of GABA,inhibit the activity of PAO and DAO,delay the degradation rate of polyamines,and maintaining the level of polyamines in apricot fruit,D-Arg treatment inhibits the activity of ADC,ODC and SAMDC in apricot fruit,impedes the production of Put,enhanced the activity of PAO and DAO,accelerated the degradation of polyamines,resulting in decreased levels of polyamines,acting on the apricot fruit senescence.(3)Spd treatment could induce the changes of endogenous PAs content in Saimaiti apricot under different temperature storage conditions.Spd treatment increased the content of Spm and Spd,decreased the release of ethylene,and the ratio of Spd/Eth,Spm/Eth increased,under normal temperature,Spd treatment could reduce the content of Put,and the ratio of Put/Eth decreased;D-Arg treatment reduced Spm,Spd,Put content and increased ethylene release.Meanwhile,the ratios of Spd/Eth,Spm/Eth and Put/Eth decreased.This indicated that Spd treatment could regulate the endogenous polyamine levels of apricot fruit,reduce ethylene release,and the ratio of PAs to Eth was related to its content.(4)A total of 246.19 Gb Clean Data was obtained,and the percentage of Q30 bases in each sample was not less than 92.59% through transcriptome sequencing,.A total of 71,406 Unigenes were assembled from the head with Trinity software,and the N50 was 2,245 nt.According to biological analysis,PaSAMDC,PaADC,PaSPDS,and PaSPMS genes were obtained,these four genes associated with polyamine synthesis.The expression levels of PaSAMDC,PaADC,PaSPDS,and PaSPMS were different in Saimaiti fruit stored at low temperature.Spd through up-regulates PaSAMDC,PaADC,PaSPDS,and PaSPMS gene expression,regulate the synthesis of polyamines and delays the ripening of apricot fruit.D-Arg treatment significantly decreased the PaADC gene expression in apricot fruit compared with PaSAMDC,PaSPDS and PaSPMS genes.In summary,exogenous Spd treatment can delay the change of softening-related enzyme activity,regulates the activity of polyamine metabolism related enzymes and polyamine synthesis related genes,increase polyamine content,led S-adenosylmethionine conversed to PAs,thereby reduce the release of ethylene,delaying fruit ripening and senescence and maintaining the storage quality of apricots fruit.