Preliminary Study On Regulation Mechanism Of Slow Melting Flesh Characteristics In Peach

Peach（Prumus persica（L.）.Batsch）belongs to Prunus of Rosaceae.Peach is a typical respiration climacteric fruit and softening very fast in late fruit development,which resulted in short shelf life and high postharvest losses.Compared with the traditional melting flesh peach（MF）,slow melting flesh peach（SMF）fruit can maintain high firmness during ripening,have longer shelf life,and finally release ethylene to soften.SMF fruit not only has excellent storage capacity,but maintains the unique taste and flavour of traditional honey peach.Therefore,SMF has become an important breeding objective in many countries.However,to date,research on SMF regulatory mechanisms is still very limited.In this study,we firstly analyzed the physiological character of SMF peach ripening and softening,mapped the related characteristics by BSA sequencing,and developed related molecular markers.Furthermore,we cloned the Pp YUC11 promoter,and one bHLH transcription factor regulating Pp YUC11 was screened by yeast one-hybrid screen.And we analyzed the regulation mechanism of SMF,in order to provide theoretical basis for molecular breeding of SMF peach.The main results are as follows:Compared with MF peach‘CN13’,SMF peach‘Chunrui’had the characteristic of delayed ethylene release after harvest.And SMF fruits can stay the tree for a long time.The expression analysis of ripening related genes showed that the ethylene biosynthesis key gene Pp ACS1 and auxin biosynthesis gene Pp YUC11 in SMF peach fruits were delayed,which suggested that the difference SMF and MF may occur in the upstream of Pp YUC11.Based on the population MF‘Chunmei’×SMF‘Chunxue’,we identified the phenotypic and analysised genetic regularity of 75 _F1hybrid plants.Results suggested that SMF trait may be dominant and controlled by a single gene or major QTL.Then,according to fruit staying the tree time,two extreme pools（23 MF peach and 25 SMF peach）were used for BSA-sequencing.The target traits were located on chromosome 2 with interval of 160 Kb（Pp02:4,658,802-4,817,924）and chromosome 4 with interval of 7.58 Mb（Pp04:17,298,854-24,878,089）.There are 332 genes in the candidate region,and KASP markers were developed in the chromosome 4 region with an accuracy of 72.0%.Acquisition of key transcription factors upstream of Pp YUC11:Using Pp YUC11 promoter as bait,using yeast-one-hybrid,one bHLH transcription factors was screened,closely related to fruit ripening:Pp PRE1（Prupe.3G269500）.Subcellular localization showed that Pp PRE1 was located in the nucleus.PpPRE1 related to fruit ripening:the results of yeast one-hybrid experiment showed that Pp PRE1could interact with Pp YUC11 promoter.The results of tobacco double luciferase and peach fruit transient expression analysis showed that Pp PRE1 was transcriptional activators,which involved in peach fruit ripening and softening by regulating Pp YUC11.In summary,SMF trait was mapped by BSA sequencing and a KASP marker was developed for the breeding of SMF peach.Pp PRE1 was further cloned and analyzed,which can directly activated the transcription of a flavin monooxygenase gene Pp YUC11 in IAA biosynthesis and finally regulated peach fruit ripening.This provides a theoretical basis and gene resources for further study on the molecular mechanism of fruit ripening and softening.