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31.
J. M. Hibberd R. A. Bungard M. C. Press W. D. Jeschke J. D. Scholes W. P. Quick 《Planta》1998,205(4):506-513
Cells capable of photosynthesis in the parasitic angiosperm Cuscuta reflexa Roxb. (dodder) are highly localized. Immunolocalization of ribulose-1,5 bisphosphate carboxylase-oxygenase (Rubisco) and
autofluorescence of chlorophyll in transverse sections of stems showed that they were largely restricted to a band of cells
adjacent to the vascular bundles, consequently, the concentrations of Rubisco and chlorophyll were low per unit area or fresh
weight. When 14CO2 was supplied to stem segments of C. reflexa it preferentially accumulated in these cells adjacent to the vasculature. Although the conductance for CO2 movement to the cells containing chlorophyll and Rubisco was very low, both the light reactions and dark reactions of photosynthesis
appeared to be functional. De-epoxidation of the xanthophyll-cycle pigments after exposure to high light, and the chlorophyll
fluorescence parameters, photochemical quenching (qP), non-photochemical quenching (NPQ) and the quantum efficiency of photosystem
II (φPSII) responded normally to changes in photon flux density, indicating functional light-driven electron transport. The
response of CO2 exchange to photon flux density followed a typical hyperbolic curve, and positive rates of CO2 fixation occurred when external CO2 was increased to 5%. We propose that CO2 for carbon assimilation is derived from internally respired CO2 and that this layer of photosynthetic cells makes a positive contribution to the carbon budget of C. reflexa.
Received: 23 October 1997 / Accepted: 16 December 1997 相似文献
32.
Squalene synthase (SQS) catalyzes the first step of sterol/hopanoid biosynthesis in various organisms. It has been long recognized that SQSs share a common ancestor with carotenoid synthases, but it is not known how these enzymes selectively produce their own product. In this study, SQSs from yeast, human, and bacteria were independently subjected to directed evolution for the production of the C30 carotenoid backbone, dehydrosqualene. This was accomplished via high-throughput screening with Pantoea ananatis phytoene desaturase, which can selectively convert dehydrosqualene into yellow carotenoid pigments. Genetic analysis of the resultant mutants revealed various mutations that could effectively convert SQS into a “dehydrosqualene synthase.” All of these mutations are clustered around the residues that have been proposed to be important for NADPH binding. 相似文献
33.
Flower colours and the composition of pigments in the perianths of five cultivars of Disa orchids were analyzed. Carotenoids were major pigment components in the orange-red flowers of ‘Dawn Angel’. We identified two types of pigment composition in the red flowered cultivars: ‘San Francisco’ contained more carotenoids and less anthocyanins, while ‘Marlene’ contained more anthocyanins than carotenoids. The red-purple flowered cultivars, only contained slight amounts of carotenoids, and the red-purple colour was attributed to the relatively high density of a cyanidin-based anthocyanin. The importance of the characterization of pigments in the perianths of orchid has been discussed in both breeding for flower colour improvement and chemotaxonomy. 相似文献
34.
Ratnakar Vallabhaneni Louis M.T. Bradbury 《Archives of biochemistry and biophysics》2010,504(1):104-111
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38.
Agrobacterium-mediated transformation of Solanum phureja 总被引:1,自引:0,他引:1
A population of transgenic plants was produced by the transformation of internodal explants of Solanum phureja, DB337/37 (the cultivar Mayan Gold) using an Agrobacterium tumefaciens LBA4404-based vector containing a phytoene synthase gene (crtB). The regeneration strategy utilised a two-step protocol, with a 12-day callus induction stage mediated by 1.07 M -napthaleneacetic acid (NAA), 7.10 M zeatin riboside and 0.06 M gibberellic acid (GA3), followed by a prolonged (up to 90 day) shoot induction stage on medium containing 0.11 M NAA, 7.10 M zeatin riboside and 0.06 M GA3 supplemented with kanamycin at 50 mg l–1 as the selection agent. Southern analysis of the transgenic population revealed that the transgene copy number varied between one and five in the lines tested. Northern blot analysis showed significant expression of the introduced crtB gene in some lines during tuber development. Cytological analysis of the material showed a high incidence of chromosome doubling in the transgenic population with over 80% of all lines tested having doubled their chromosome complement during the transformation process. 相似文献
39.
Oxygen and hydrogen peroxide enhance light-induced carotenoid synthesis in Neurospora crassa 总被引:2,自引:0,他引:2
Previously, we found that intracellular reactive oxygen species (ROS) affect photomorphogenesis in Neurospora crassa. In this study, we investigated the physiological roles of ROS in the response to light and found that the exposure of mycelia to air was important for the light-induced carotenogenesis. Mycelia treated with a high concentration of O(2) gas and H(2)O(2) to release ROS showed an enhancement of light-induced carotenoid accumulation and the expression of gene related to light-inducible carotenogenesis. These results suggested that stimuli caused by the exposure of the mycelia to air containing O(2) gas triggered the light-induced carotenoid synthesis. 相似文献
40.
Adjele Wilson James N. Kinney Petrus H. Zwart Claire Punginelli Sandrine D'Haene Fran?ois Perreau Michael G. Klein Diana Kirilovsky Cheryl A. Kerfeld 《The Journal of biological chemistry》2010,285(24):18364-18375
The photoprotective processes of photosynthetic organisms involve the dissipation of excess absorbed light energy as heat. Photoprotection in cyanobacteria is mechanistically distinct from that in plants; it involves the orange carotenoid protein (OCP), a water-soluble protein containing a single carotenoid. The OCP is a new member of the family of blue light-photoactive proteins; blue-green light triggers the OCP-mediated photoprotective response. Here we report structural and functional characterization of the wild type and two mutant forms of the OCP, from the model organism Synechocystis PCC6803. The structural analysis provides high resolution detail of the carotenoid-protein interactions that underlie the optical properties of the OCP, unique among carotenoid-proteins in binding a single pigment per polypeptide chain. Collectively, these data implicate several key amino acids in the function of the OCP and reveal that the photoconversion and photoprotective responses of the OCP to blue-green light can be decoupled. 相似文献