title: Arabidopsis OR proteins are the major posttranscriptional regulators of phytoene synthase in controlling carotenoid biosynthesis.
abstract: Carotenoids are indispensable natural pigments to plants and humans. Phytoene synthase (PSY), the rate-limiting enzyme in the carotenoid biosynthetic pathway, and ORANGE (OR), a regulator of chromoplast differentiation and enhancer of carotenoid biosynthesis, represent two key proteins that control carotenoid biosynthesis and accumulation in plants. However, little is known about the mechanisms underlying their posttranscriptional regulation. Here we report that PSY and OR family proteins [Arabidopsis thaliana OR (AtOR) and AtOR-like] physically interacted with each other in plastids. We found that alteration of OR expression in Arabidopsis exerted minimal effect on PSY transcript abundance. However, overexpression of AtOR significantly increased the amount of enzymatically active PSY, whereas an ator ator-like double mutant exhibited a dramatically reduced PSY level. The results indicate that the OR proteins serve as the major posttranscriptional regulators of PSY. The ator or ator-like single mutant had little effect on PSY protein levels, which involves a compensatory mechanism and suggests partial functional redundancy. In addition, modification of PSY expression resulted in altered AtOR protein levels, corroborating a mutual regulation of PSY and OR. Carotenoid content showed a correlated change with OR-mediated PSY level, demonstrating the function of OR in controlling carotenoid biosynthesis by regulating PSY. Our findings reveal a novel mechanism by which carotenoid biosynthesis is controlled via posttranscriptional regulation of PSY in plants.
authors: Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, US Department of Agriculture, 14850; Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853; and.
authors: Xiangjun
authors: X
authors: Zhou
authors: Faculty of Biology II, University of Freiburg, D79104 Freiburg, Germany ll37@cornell.edu ralf.welsch@biologie.uni-freiburg.de.
authors: Ralf
authors: R
authors: Welsch
authors: Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, US Department of Agriculture, 14850;
authors: Yong
authors: Y
authors: Yang
authors: Faculty of Biology II, University of Freiburg, D79104 Freiburg, Germany.
authors: Daniel
authors: D
authors: Álvarez
authors: Faculty of Biology II, University of Freiburg, D79104 Freiburg, Germany.
authors: Matthias
authors: M
authors: Riediger
authors: Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, US Department of Agriculture, 14850; Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853; and.
authors: Hui
authors: H
authors: Yuan
authors: Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, US Department of Agriculture, 14850;
authors: Tara
authors: T
authors: Fish
authors: Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, US Department of Agriculture, 14850;
authors: Jiping
authors: J
authors: Liu
authors: Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, US Department of Agriculture, 14850;
authors: Theodore W
authors: TW
authors: Thannhauser
authors: Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, US Department of Agriculture, 14850; Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853; and ll37@cornell.edu ralf.welsch@biologie.uni-freiburg.de.
authors: Li
authors: L
authors: Li
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002338:Carotenoids / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase / Q000235:genetics*; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D018087:Plastids / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D013329:Structure-Activity Relationship
chemical_list: D029681:Arabidopsis Proteins; D002338:Carotenoids; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase
keywords: Arabidopsis; OR; carotenoid; phytoene synthase; posttranscriptional regulation