Carotenoid cleavage dioxygenases(CCDs) are a class of enzymes in plants involved in the biosynthesis of apocarotenoids,such as phytohormones,flavour compounds,and other compounds with yet unknown functions.To date,several CCDs have been functionally characterised in plants,but little is known about the CCD4 members.A carotenoid cleavage dioxygenase 4 gene(LcCCD4) was isolated from the leaves of wolfberry(Lycium chinense) to gain insight into its biological function.Multiple sequence alignment and phylogenetic analyses showed that the deduced amino acid sequence of LcCCD4 shares high homology with that of CCD4 proteins from other plants.Expression analysis using semi-quantitative polymerase chain reaction revealed that LcCCD4 was strongly expressed in leaves and flowers and that the expression level was in accordance with β-carotene concentration.LcCCD4 transcripts in fruits tended to decrease as carotenoids accumulated.Recombinant expression of LcCCD4 cleaved β-carotene to produce P-ionone in in vivo assays.These results show that LcCCD4 is a CCD gene that may be involved in producing aromatic apocarotenoids in leaves and flowers,whereas it may be involved in controlling carotenoid accumulation in fruits.
Xiaowei TianJing JiGang WangChao JinCuicui JiaZhaodi Li
Carotenoid isomerase(CRTISO)is a key enzyme that catalyzes the conversion of cis-lycopene to alltrans lycopene. In this study, we isolated and characterized the CRTISO gene from Lycium chinense(Lc CRTISO) for the first time. The open reading frame of Lc CRTISO was 1 815 bp encoding a protein of 604 amino acids with a molecular mass of 66.24 k Da. Amino acid sequence analysis revealed that the Lc CRTISO had a high level of similarity to other CRTISO. Phylogenetic analysis displayed that Lc CRTISO kept a closer relationship with the CRTISO of plants than with those of other species. Semi-quantitative PCR analysis indicated that Lc CRTISO gene was expressed in all tissues tested with the highest expression in maturing fruits. The overexpression of Lc CRTISO gene in transgenic tobacco resulted in an increase of total carotenoids in the leaves with β-carotene and lutein being the predominants. The results obtained here clearly suggested that the Lc CRTISO gene was a promising candidate for carotenoid production.
