title: Fibrillin 5 Is Essential for Plastoquinone-9 Biosynthesis by Binding to Solanesyl Diphosphate Synthases in Arabidopsis.
abstract: Fibrillins are lipid-associated proteins in plastids and are ubiquitous in plants. They accumulate in chromoplasts and sequester carotenoids during the development of flowers and fruits. However, little is known about the functions of fibrillins in leaf tissues. Here, we identified fibrillin 5 (FBN5), which is essential for plastoquinone-9 (PQ-9) biosynthesis in Arabidopsis thaliana. Homozygous fbn5-1 mutations were seedling-lethal, and XVE:FBN5-B transgenic plants expressing low levels of FBN5-B had a slower growth rate and were smaller than wild-type plants. In chloroplasts, FBN5-B specifically interacted with solanesyl diphosphate synthases (SPSs) 1 and 2, which biosynthesize the solanesyl moiety of PQ-9. Plants containing defective FBN5-B accumulated less PQ-9 and its cyclized product, plastochromanol-8, but the levels of tocopherols were not affected. The reduced PQ-9 content of XVE:FBN5-B transgenic plants was consistent with their lower photosynthetic performance and higher levels of hydrogen peroxide under cold stress. These results indicate that FBN5-B is required for PQ-9 biosynthesis through its interaction with SPS. Our study adds FBN5 as a structural component involved in the biosynthesis of PQ-9. FBN5 binding to the hydrophobic solanesyl moiety, which is generated by SPS1 and SPS2, in FBN5-B/SPS homodimeric complexes stimulates the enzyme activity of SPS1 and SPS2.
authors.affiliation: Department of Agricultural Biotechnology, National Academy of Agricultural Science, Rural Development Administration, Jeonju 54874, Republic of Korea.
authors.forename: Eun-Ha
authors.initials: EH
authors.lastname: Kim
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.
authors.forename: Yongjik
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Agricultural Biotechnology, National Academy of Agricultural Science, Rural Development Administration, Jeonju 54874, Republic of Korea hukim64@korea.kr.
authors.forename: Hyun Uk
authors.identifier: http://orcid.org/0000-0002-4566-3057
authors.initials: HU
authors.lastname: Kim
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D002839:Chromans / Q000378:metabolism; D000071837:Fibrillins / Q000235:genetics / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D009154:Mutation; D010788:Photosynthesis; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified; D018087:Plastids / Q000378:metabolism; D010971:Plastoquinone / Q000378:metabolism*; D036226:Seedlings / Q000201:enzymology / Q000235:genetics; D024505:Tocopherols / Q000378:metabolism; D014810:Vitamin E / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002839:Chromans; D000071837:Fibrillins; D014810:Vitamin E; C013649:plastochromanol 8; D006861:Hydrogen Peroxide; D019883:Alkyl and Aryl Transferases; C022644:trans-octaprenyltranstransferase; D010971:Plastoquinone; D024505:Tocopherols