ABSTRACTIn the ethylene signalling pathway, EIN2is an essential signal transducer linking ethylene perception on endoplasmic reticulum to transcriptional regulation in the nucleus, EIN3/EIL1transcription factors initiate various responses leading to an ethylene response, and EBFsfunction in ethylene perception by regulating EIN3/EIL1turnover. In this work, we isolated and characterised three EIN3homologs (CpEIN3a, CpEIN3b, and CpEIL1), and two EBFhomologs (CpEBF1and 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 CpEBF1/2were negative regulators in terms of papaya fruit ripening under exogenous ethylene treatment while CpEIN3awas a positive one, CpEIN3awas 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 CpEBF1/2are 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.