Abstract: A cDNA encoding PaCCD1 was cloned from the fruit of‘Luntai Xiaobaixing’apricot based on RNA-sequence by rapid-amplification of cDNA ends（RACE）. The complete cDNA of PaCCD1 was 1 885 bp. Sequences analysis indicated that the opening reading frame of PaCCD1 was 1 644 bp and it encoded 547 amino acids. The molecular weight of PaCCD1 protein is 61.699 kD. Amino acid sequence alignment showed that PaCCD1 was similar to other CCD1 proteins. They all shared typical conserved domains including four conserved histidine residues，two semi-conserved glutamate residues and one semi-conserved aspartate residues. Bioactive site analysis showed that PaCCD1 protein had many glycosylation and phosphorylation sites. Phylogenetic analysis indicated that PaCCD1 protein was at the same branch of the tree with AtCCD1 protein，and the genetic relationship is the closest with PpCCD1（Prunus persica）and CmCCD1（melon）. Real time PCR analysis showed that PaCCD1 expressed the highest in fruitlets，next in flower，but has no expression in roots，leaves and one-year branch，exhibiting a tissue-specific expression. Additionally，the expression levels of PaCCD1 in peels and pulps were remarkably up-regulated during fruit development and ripening，the content of the main carotenoids in apricot fruit，β-carotene and lutein，presented a significant decrease during this process，while the contents of the apocarotenoid aroma compounds，dihydro-β-ionone，β-ionone and β-damascenone，increased significantly. A PaCCD1 expression protein in vitro was acquired by transforming the target gene in E. coli. Feeding the protein with different carotenoids as specific substrates showed that the PaCCD1 protein can absorb β-carotene，and produce dihydro-β-ionone and β-ionone quickly，also can absorb lutein and produce β-damascenone. Based on these results，we inferred that PaCCD1 may be the key gene controlling apocarotenoid aroma volatiles formation in apricot fruit.

Key words: apricot, apocarotenoid, aroma, carotenoid cleavage dioxygenase, molecular cloning, gene function