Publications

• Cloning of tangerine from tomato reveals a carotenoid isomerase essential for the production of beta-carotene and xanthophylls in plants.

  Isaacson T., Ronen G., Zamir D., Hirschberg J.

  Carotenoid biosynthesis in plants has been described at the molecular level for most of the biochemical steps in the pathway. However, the cis-trans isomerization of carotenoids, which is known to occur in vivo, has remained a mystery since its discovery five decades ago. To elucidate the molecula ... >> More

  Carotenoid biosynthesis in plants has been described at the molecular level for most of the biochemical steps in the pathway. However, the cis-trans isomerization of carotenoids, which is known to occur in vivo, has remained a mystery since its discovery five decades ago. To elucidate the molecular mechanism of carotenoid isomerization, we have taken a genetic map-based approach to clone the tangerine locus from tomato. Fruit of tangerine are orange and accumulate prolycopene (7Z,9Z,7'Z,9'Z-tetra-cis-lycopene) instead of the all-trans-lycopene, which normally is synthesized in the wild type. Our data indicate that the tangerine gene, designated CRTISO, encodes an authentic carotenoid isomerase that is required during carotenoid desaturation. CRTISO is a redox-type enzyme structurally related to the bacterial-type phytoene desaturase CRTI. Two alleles of tangerine have been investigated. In tangerine(mic), loss of function is attributable to a deletion mutation in CRTISO, and in tangerine(3183), expression of this gene is impaired. CRTISO from tomato is expressed in all green tissues but is upregulated during fruit ripening and in flowers. The function of carotene isomerase in plants presumably is to enable carotenoid biosynthesis to occur in the dark and in nonphotosynthetic tissues. << Less

  Plant Cell 14:333-342(2002) [PubMed] [EuropePMC]

• Cloning and functional characterization of the maize carotenoid isomerase and beta-carotene hydroxylase genes and their regulation during endosperm maturation.

  Li Q., Farre G., Naqvi S., Breitenbach J., Sanahuja G., Bai C., Sandmann G., Capell T., Christou P., Zhu C.

  In order to gain further insight into the partly-characterized carotenoid biosynthetic pathway in corn (Zea mays L.), we cloned cDNAs encoding the enzymes carotenoid isomerase (CRTISO) and β-carotene hydroxylase (BCH) using endosperm mRNA isolated from inbred line B73. For both enzymes, two distin ... >> More

  In order to gain further insight into the partly-characterized carotenoid biosynthetic pathway in corn (Zea mays L.), we cloned cDNAs encoding the enzymes carotenoid isomerase (CRTISO) and β-carotene hydroxylase (BCH) using endosperm mRNA isolated from inbred line B73. For both enzymes, two distinct cDNAs were identified mapping to different chromosomes. The two crtiso cDNAs (Zmcrtiso1 and Zmcrtiso2) mapped to unlinked genes each containing 12 introns, a feature conserved among all crtiso genes studied thus far. ZmCRTISO1 was able to convert tetra-cis prolycopene to all-trans lycopene but could not isomerize the 15-cis double bond of 9,15,9'-tri-cis-ζ-carotene. ZmCRTISO2 is inactivated by a premature termination codon in B73 corn, but importantly the mutation is absent in other corn cultivars and the active enzyme showed the same activity as ZmCRTISO1. The two bch cDNAs (Zmbch1 and Zmbch2) mapped to unlinked genes each coding sequences containing five introns. ZmBCH1 was able to convert β-carotene into β-cryptoxanthin and zeaxanthin, but ZmBCH2 was able to form β-cryptoxanthin alone and had a lower overall activity than ZmBCH1. All four genes were expressed during endosperm development, with mRNA levels rising in line with carotenoid accumulation (especially zeaxanthin and lutein) until 25 DAP. Thereafter, expression declined for three of the genes, with only Zmcrtiso2 mRNA levels maintained by 30 DAP. We discuss the impact of paralogs with different expression profiles and functions on the regulation of carotenoid synthesis in corn. << Less

  Transgenic Res 19:1053-1068(2010) [PubMed] [EuropePMC]

• ZEBRA2, encoding a carotenoid isomerase, is involved in photoprotection in rice.

  Chai C., Fang J., Liu Y., Tong H., Gong Y., Wang Y., Liu M., Wang Y., Qian Q., Cheng Z., Chu C.

  "zebra" mutants have alternating green and chlorotic crossbands on leaf blades and are widely distributed in monocotyledonous crops. Most recently, we cloned the first responsible gene from rice, ZEBRA2, which also leads to the phenotype of rice preharvest sprouting. ZEBRA2, a single-copy gene in ... >> More

  "zebra" mutants have alternating green and chlorotic crossbands on leaf blades and are widely distributed in monocotyledonous crops. Most recently, we cloned the first responsible gene from rice, ZEBRA2, which also leads to the phenotype of rice preharvest sprouting. ZEBRA2, a single-copy gene in the rice genome, encodes a carotenoid isomerase (CRTISO), the key enzyme catalyzing the conversion of cis-lycopene to all-trans lycopene. ZEBRA2 shares high identity with known CRTISOs from other species. Expression analysis via both RT-PCR and ZEBRA2-promoter-β-glucuronidase (GUS) transgenic rice indicates that ZEBRA2 is predominantly expressed in mesophyll cells of mature leaves where active photosynthesis occurs. Consistent with the alteration in agronomic traits, the zebra2 mutant exhibits decreased photosynthetic rate and chlorophyll content. Mutation of the ZEBRA2 gene results in the accumulation of all-trans-lycopene precursor, prolycopene (7Z,9Z,7'Z,9'Z tetra cis-lycopene), in dark-grown zebra2 tissues. Light-grown zebra2 mutant exhibits the characteristic "zebra" phenotype and decreased level of lutein, the xanthophyll that is essential for efficient chl triplet quenching. More severe phenotype of the zebra2 mutant under high light intensity indicates that "zebra" phenotype might be caused by photooxidative damages. We conclude that ZEBRA2 is involved in photoprotection in rice. << Less

  Plant Mol Biol 75:211-221(2011) [PubMed] [EuropePMC]