Chlorophyll Degradation Products Influenced The Ripening Of Tomato And Banana

Chlorophylls(CHL)as the most abundant nature pigment on the earth,participate the photosynthesis of plants.It is well known about the biosynthetic and degradation pathways of chlorophylls and chlorophyll degradation is the sign of fruit ripening and leaf senescence.C hlorophyll degradation is often considered as a passive process,however,our previous study found that chlorophyll degradationwas an early activated event,prior to the decline of fruit hardnessand starch.As a result,what is the biological significance of the early initiation of chlorophyll degradation in the process of postharvest fruit ripening? In the present study,in vitro culture oftomato(Solanum lycopersicum,Cv.Ailsa Craig)and banana(Musa acuminata AAA group,Cv.Carvendish)peelwere used as experimental system to investigatethe function of chlorophyll degradation products in the process of climacteric fruit ripening.Main results are as follows:1.Preparation of highly purified chlorophyll degradation productsExtraction and purification of chlorophyll of high purity,using the principle of saponification reaction,prepare saponified chlorophyll(Saponified-Chl).Using Ecoli expression method to obtain Citru chlorophyllase of high activity,by p ET-55-CLH that was gifted by Dr.Yoram Eyal,department of fruit tree science,ARO Volcani center,Israel,prepare chlorophyllide(Chlide).HPLC method were used to detect the purity of chlorophyll and its degradation products.2.Chlorophyll degradation products influencedthe tomato ripening in vitro cultureGreen mature tomato fruit was used in the in vitro culture.The results showed that in the process of the culture,control and ethylene treated tomato peelswere still yellowish greenat 6 d,whilethe chlorophyll degradation products treatedpeels appeared red at 6 d.In the process of in vitro culture,the chlorophyll fluorescence Fv/Fm and chlorophyll content of all treatment groups declined,while the content of lycopene increased.Compared with control and ethylene treatment,chlorophyll degradation products promotedthe rapid decline of Fv/Fm and chlorophyll content in tomato peel,and induced a substantial accumulation of lycopene in the peel.In addition,the chlorophyll degradation products led to the early activation of key genes SlPAO,SlPPH,SlSGRin the chlorophyll degradation pathway,and significant induction of SlPSY1,SlGGPS2,SlPDS,andSlZDS,the key genes of lycopene synthesis pathway were induced.Compared with the control,chlorophyll degradation products significantly induced to ethylene biosynthesis relatedgenes,SlACS2,SlACS4 and SlACO1,and induced the expression of transcription factors SlETR4 extensive at 3 d,while SlERF1 A,SlERF2b and Sl RIN expressed at 6 d.The saponification chlorophyll always had more efficient than the chlide.The results above showed that the chlorophyll degradation products can promote tomato peel of chlorophyll degradation and synthesis of lycopene,what's more induced the synthesis and signal transduction ofethylene.3.Chlorophyll degradation products influence thebanana ripening in vitro cultureGreen mature tomato fruit was used in the in vitro culture.In the culture,control treated banana peel was still yellowish greenat 6 d,but the ethylene and chlorophyll degradation products treated peels transformed from green to yellow.Chlorophyll fluorescence Fv/Fm,chlorophyll content and starch content ofall treatment groups declined.The Fv/Fm,chlorophyll content and starch contentof ethylene treatment group decreased quickliest,and then the chlorophyll degradation products group,control drop slowest.Chlorophyll degradation products,similar to ethylene treatment and the effect just followed theethylene: promote pectin methyllipase MaPEand the ethylene biosynthesis relatedgenes MaACS and MaACOexpressed increasedly,what is more,urge ripening gene ribulose 1,5-bishosphate carboxylase small MaSSUdecline accelerated significantly.The ethylene and chlorophyll degradation products treatment main induced MaRIN responsedat 3 d,and the expression level ofMaERF2 and MaERF5 are rising constantly in the latecultivating.Chlorophyll degradation products and ethylene treatment can promote the banana peel chlorophyll content declined,ethylene promote the expression of the key gene MaPAO,MaPPH,MaCLH,MaNYC in theprocess of chlorophyll degradation,but chlorophyll degradation products doesn't and even restrain obviously.The activityof POD enzyme and POD PAGEtests showed that compared with the control,the chlorophyll degradation products treated peelscontains higher content of POD enzyme at 3 d.As a result,we speculate that the chlorophyll degradation products might promote banana peel chlorophyll degradation not following the classical PAO degradation pathways,just through the oxidation degradation pathway.The results above show that the chlorophyll degradation products can promote banana peel senescent,inducedthe synthesis and signal transduction of ethylene,and promote the banana peel by oxidation bleaching degradation of chlorophyll.Comprehensive the above results,the main conclusions of this paper: the chlorophyll degradation products can promote climacteric fruit tomato and banana ripening,and can induce the synthesis of ethylene.