title: Cloning and selection of carotenoid ketolase genes for the engineering of high-yield astaxanthin in plants.
abstract: β-Carotene ketolase (BKT) catalyzes the rate-limiting steps for the biosynthesis of astaxanthin. Several bkt genes have been isolated and explored to modify plant carotenoids to astaxanthin with limited success. In this study, five algal BKT cDNAs were isolated and characterized for the engineering of high-yield astaxanthin in plants. The products of the cDNAs showed high similarity in sequence and enzymatic activity of converting β-carotene into canthaxanthin. However, the enzymes exhibited extremely different activities in converting zeaxanthin into astaxanthin. Chlamydomonas reinhardtii BKT showed the highest conversion rate (ca 85%), whereas, Neochloris wimmeri BKT exhibited very poor activity of ketolating zeaxanthin. Expression of C. reinhardtii BKT in tobacco led to a twofold increase of total carotenoids in the leaves with astaxanthin being the predominant. The bkt genes described here provide a valuable resource for metabolic engineering of plants as cell factories for astaxanthin production.
authors.affiliation: Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China. huangjc@mail.kib.ac.cn
authors.forename: Junchao
authors.initials: J
authors.lastname: Huang
authors.forename: Yujuan
authors.initials: Y
authors.lastname: Zhong
authors.forename: Gerhard
authors.initials: G
authors.lastname: Sandmann
authors.forename: Jin
authors.initials: J
authors.lastname: Liu
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
mesh_terms: D020418:Algal Proteins / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D002338:Carotenoids / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry; D016825:Chlamydomonas reinhardtii / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D000460:Chlorophyta / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D060847:Metabolic Engineering; D008969:Molecular Sequence Data; D010105:Oxygenases / Q000235:genetics* / Q000378:metabolism; D018515:Plant Leaves / Q000737:chemistry / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014026:Nicotiana / Q000737:chemistry / Q000201:enzymology / Q000235:genetics; D019076:Transgenes; D024341:Xanthophylls / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D065146:Zeaxanthins
chemical_list: D020418:Algal Proteins; D018076:DNA, Complementary; D024341:Xanthophylls; D065146:Zeaxanthins; D002338:Carotenoids; C005948:astaxanthine; D010105:Oxygenases; C093259:beta-carotene ketolase