The Key Genes in the Transformation of Ethylene Production System Ⅰand Ⅱ of'Hongyang'Kiwifruit
In this study,'Hongyang'kiwifruit was used as raw material.We used ethylene as an intervention method to investigate the changes in physicochemical indexes,ethylene production rate,and the activities of ACS and ACO,the key enzymes involved in ethylene production during postharvest storage period.In addition,the expression differences of each member of the gene family affecting ACS and ACO were also studied using real-time quantitative PCR combined with bioinformatics analysis,and the key genes for the transition from ethylene production system Ⅰ to Ⅱ were cloned.The results showed that the hardness of'Hongyang'kiwifruit decreased from 8.7 kg/cm2 to 0.02 kg/cm2 and the content of soluble solids increased from 8.1％to 16.9％during postharvest storage,and the ACS and ACO activities in both the ethylene intervention and non-intervention groups showed a trend of first increase and then decrease,which was consis-tent with the trends of respiratory intensity and ethylene release rate.Besides,The ACS,ACO activity and respiration intensity of the samples in the non-intervention group reached their peaks on the 9th day,and the ethylene release rate peaked on the 7th day,while the ethylene treatment group all peaked on the 5th day,indicating that ethylene could accelerate the arrival of the kiwifruit respiration peak,ethylene release rate peak and the peaks of ACS,ACO activity.Six ACO genes were successfully cloned from'Hongyang'kiwifruit fruit,named as AcACO1-6.The sequence of the cod-ing region of AcACO1-6 was 1 101-1 270 bp,encoding 352-402 amino acids,and the nucleotide sequence homology was 28.3％-99.3％.Moreover,all ACO genes had the same conserved structural domain PLN02299,which had ACO ac-tivity.Finally,the qRT-PCR results showed that the relative expression of ACO is 500 times higher than that of ACS,and there was a high consistency between the expression changes of AcACO1 and AcACO3 in the ACO gene family and changes in ethylene production and enzyme activity(R＞0.85).Particularly,their promoter sequences were enriched with cis-acting elements involved in transcriptional regulation.Overall,the findings suggested that AcACO1 and AcACO3 were pivotal genes in the transition from ethylene production system Ⅰ to system Ⅱ.
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