Molecular Cloning And Expression Analysis Of Ein2, Ein3/Eil, And Ebf Genes During Papaya Fruit Development And Ripening

In the ethylene signalling pathway, EIN2 is an essential signal transducer linking ethylene perception on endoplasmic reticulum to transcriptional regulation in the nucleus, EIN3/EIL1 transcription factors initiate various responses leading to an ethylene response, and EBFs function in ethylene perception by regulating EIN3/EIL1 turnover. In this work, we isolated and characterised three EIN3 homologs (CpEIN3a, CpEIN3b, and CpEIL1), and two EBF homologs (CpEBF1 and CpEBF2) from papaya fruits. During the fruit development, the transcripts of all these genes were accumulated at a low level before reaching a maximum in the third month, then showed a decrease. Exogenous ethylene application and 1-MCP treatment had different effects on the expression of these genes. The correlations between various physiological characteristics with the gene expressions showed that CpEIN3b, CpEIL1, and CpEBF1/2 were negative regulators in terms of papaya fruit ripening under exogenous ethylene treatment while CpEIN3a was a positive one, CpEIN3a was negatively correlated with the respiration rate and ethylene production of papaya fruits under 1-MCP treatment. It is suggested that CpEIN2, CpEIN3a/b, CpEIL1, and CpEBF1/2 are development- and ripening-related genes in papaya fruits. These results provide new insights into the understanding of the ethylene signalling cascade in papaya fruit development and ripening.