Abstract: In order to explore molecular mechanism of fruit ripening and the key softening-related genes，cDNA-AFLP technique was used to identify differentially expressed genes during papaya fruit ripening. Fifty transcript-derived fragments（TDFs）were obtained from the analysis of semi-yellow and color-break stage of papaya fruit. Bioinformatics analysis showed that 28 TDFs were homologous to the known functional genes，which could be divided into different functional groups including gene expression regulation，DNA and protein synthesis and transport，protein degradation，energy metabolism，nutrient metabolism and stress responding. Using specific primers designed from the sequences of TDFs，four differential expression genes were cloned by rapid amplification of cDNA ends（RACE）. Semi-quantitative RT-PCR analysis showed that the expression of four genes changed accordingly during fruit ripening，indicating the possible role of these genes in the ripening of papaya. 　

Key words: Carica papaya, fruit, ripening, cDNA-AFLP, differential expression, RACE