| Pear is the third most important fruit in China and China is the worldwide leader in pear production and cultivated area.Most pears belong to the respiratory-climacteric fruit,the climacteric pear fruits release massive ethylene during fruit ripening.As we all know,ethylene can promote the climacteric pear fruits ripening,ERF(Ethylene response.factor)-is the final gene of the ethylene signaling pathway that regulates ripening-related genes.In this study,aiming at the different characteristics of Chinese pear cultivars during the ripening period,Yali and Cuiguan were used as experimental materials to carry out studies on the regulation of fruit ripening by different hormones and ERF transcription factors.Studies have clarified the molecular pathways of ethylene synthesis by PbrERF24 and PbrERF912that regulate the fruit ripening of Yali and Cuiguan respectively,and explored the impact of IAA and ABA on fruit development and maturation.The main results are as follows:1.After analyzing the differences in ethylene release from mature fruits of five pear cultivars,it can be concluded that within the same time and unit weight,the release of ethylene from the European pears and ussurian pears is higher,the white pears and sand pears are followed,and the Xinjiang pears have the lowest ethylene release.Based on the study of pear storage characteristics,this experiment selected a typical respiratory climacteric species,Yali and Cuiguan,from the white pear and sand pear systems,respectively,as a test material to investigate the effects of ethylene and 1-MCP treatment on fruitsripening.The data showed that the soluble solids content of Yali pear fruit treated with 1.5?l·1-1-MCP significantly decreased.In addition,300 ppm ethylene treatment significantly promoted the fruits ripening of Cuiguan.This conclusion provides a theoretical basis for the subsequent screening of ethylene response factors that regulate fruit ripening.2.Transcriptome libraries were constructed and sequenced in pre-ripening(PF),ripening(RB),and 1-MCP treated fruits(TF).Data analysis showed that 73 candidate genes related to fruit ripening were induced by 1-MCP,among which two were positively related,namely 1-aminocyclopropane-1-carboxyla oxidase and an ERFgene(designated as AC054andERF24).Transient transformations in pear fruit revealed that over-expression of AC054 enhances transcription level of ERF24 and most ripening-related genes.Meanwhile,over-expression of ERF24 raises expression level of AC054 and partially ripening-related genes.Moreover,dual-luciferase and yeast-one-hybrid assays unravel an interaction between ERF24 and the AC054.These results suggested that the first identified ERF24 is involved in regulating fruit ripening in Chinese white pear.3.An ethylene biosynthetic gene ACS688 and another ethylene response factor ERF912 were screened outbased on transcriptome data of fruit development dynamics.The qRT-PCR validation was performed on the ethylene-treated fruit of Cuiguan,and the results showed that these genes,ERF912,ACS688and AC054 are related to the ripening of the fruit of Cuiguan.In addition,dual luciferase reporter assays and yeast one-hybrid experiments further validated the interaction of ERF912 and AC054.These results all reveal that the ethylene response factor ERF912 is involved in regulating the maturation of Cuiguan.4.Based on the above research,the study uses Cuiguan as the test material to investigate the effect of IAA and ABA treatments on fruit ripening in the five stages of fruit development.Cuiguan was treated with IAA and ABA at concentrations of 0.1 mg/L,1 mg/L,10 mg/L,100 mg/Land 1000 mg/L.Through a series of physiological indicators,the results showed that IAA and ABA treatment have a certain impact on fruit development and maturation.Especially in about 90 days after flowering,the five concentrations of IAA and ABA treatment increased the content of soluble solids in fruits,and the difference was extremely significant compared with the control. |
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