Molecular Mechanism Of Calcium Inhibiting Ethylene Synthesis During Apple Fruit Ripening

Apple?Malus domestica?fruit is a typical type of climacteric fruit,and postharvest storage is an important economic trait.The ripening process of climacteric fruits is mainly regulated by ethylene,a major plant growth regulator and plant.There are many reports that exogenous calcium solution can inhibit ethylene production,but its molecular mechanism is not clear.In this study,the fruit was soaked in 2%CaCl₂ solution after harvest and stored at room temperature.It was found that ethylene production was inhibited compared with the control.Ca²⁺can participate in the signal transduction pathway of ethylene,and the 2%Ca Cl₂solution promotes the gene expression of ERF in the ethylene signal transduction pathway.Ethylene inhibits the expression of Md ERF2 and binds to Md ACS1 promoter during apple fruit ripening.The expression of MdERF2 was promoted after treatment with 2%CaCl₂solution.In this study,the binding of transcription factor MdERF5 to Md ACS1 promoter,inhibiting the expression of Md ACS1,a key gene for ethylene synthesis,was studied,and then the molecular mechanism of ethylene synthesis was regulated during fruit maturation.The main results are as follows:1 The transcription factor MdERF5 in ethylene signal transduction pathway was cloned from the apple genome.By analyzing the expression pattern of the key enzyme gene Md ACS1 and MdACO1 and transcription factor ERF,it was found that the expression of Md ERF2 and Md ERF5 up-regulated after Ca Cl₂ treatment.2 Yeast one-hybrid?Y1H?and EMSA assay shown that MdERF5 could bind to Md ACS1promoter and GUS reporter gene activity test showed that Md ERF5 inhibited the activit y of Md ACS1 promoter.3.The results of Yeast two-hybrid?Y2H?and Pull down test showed that MdERF2 and MdERF5 could interact with each other.The results of GUS reporter gene fluorescence detection showed that the interaction between MdERF2 and MdERF5 enhanced the inhibition of Md ACS1 promoter activity.These results indicated that the interaction between MdERF2 and MdERF5 was promoted by Ca Cl₂ and the interaction between MdERF2 and MdERF5 enhanced the negative regulation of MdACS1.The molecular mechanism of calcium inhibiting ethylene synthesis was discussed.