CLONING AND EXPRESSION ANALYSIS OF OFCCD1 AND OFCCD4 GENES IN SWEET OSMANTHUS

Sweet osmanthus is an extraordinary aromatic flower, an excellent greening tree species in gardens, and a raw material for processing spice of high economic value. More than 60 main aroma components have been identified in it. According to their chemical structures, the components can be divided into terpenes, aldehydes, esters, ketones, alcohols, and other compounds. Carotenoid cleavage dioxygenase is a key enzyme in the degradation of carotenoids, which catalyzes the cleavage of carotenoids to produce a variety of products, including the floral substances alpha-ionone and beta-ionone. In order to explore the critical enzyme genes of sweet osmanthus, two CCD genes named OfCCD1 (GenBank No. OM256439) and OfCCD4 (GenBank No. OM145981) were cloned by RACE and RT-PCR and analyzed by bioinformatics and their expression pattern. The results showed that the total length of the cDNA of OfCCD1 and OfCCD4 genes were 1811 bp and 2076 bp, respectively. They both contained a complete open reading frame, 1632 bp and 1833 bp, encoding 543 aa and 610 aa, respectively. Analysis showed that both OfCCD1 and OfCCD4 were stable hydrophilic proteins with an RPE65 domain and without signal peptide cleavage sites and transmembrane regions. Phylogenetic tree results showed that OfCCD1 and OfCCD4 were closely related to the evolution of the homologous proteins of Olea europaea. Expression analysis showed that the expression of OfCCD1 was greatest in leaves at the full flowering stage, while the expression of OfCCD4 was greatest in inflorescences at the bud-eye stage; OfCCD4 had obvious tissue specificity. In conclusion, the cloning and correlation analysis of OfCCD1 and OfCCD4 genes can provide a further basis to study sweet osmanthus's floral aroma metabolism.