title: Etioplast differentiation in arabidopsis: both PORA and PORB restore the prolamellar body and photoactive protochlorophyllide-F655 to the cop1 photomorphogenic mutant.
abstract: The etioplast plastid type of dark-grown angiosperms is defined by the accumulation of the chlorophyll (Chl) precursor protochlorophyllide (Pchlide) and the presence of the paracrystalline prolamellar body (PLB) membrane. Both features correlate with the presence of NADPH:Pchlide oxidoreductase (POR), a light-dependent enzyme that reduces photoactive Pchlide-F655 to chlorophyllide and plays a key role in chloroplast differentiation during greening. Two differentially expressed and regulated POR enzymes, PORA and PORB, have recently been discovered in angiosperms. To investigate the hypothesis that etioplast differentiation requires PORA, we have constitutively overexpressed PORA and PORB in the Arabidopsis wild type and in the constitutive photomorphogenic cop1-18 (previously det340) mutant, which is deficient in the PLB and Pchlide-F655. In both genetic backgrounds, POR overexpression increased PLB size, the ratio of Pchlide-F655 to nonphotoactive Pchl[ide]-F632, and the amount of Pchlide-F655. Dramatically, restoration of either PORA or PORB to the cop1 mutant led to the formation of etioplasts containing an extensive PLB and large amounts of photoactive Pchlide-F655.
authors.affiliation: Institute for Plant Sciences, Department of Plant Genetics, LFW D31, Swiss Federal Institute of Technology (ETH), Universitatstrasse 2, CH-8092 Zurich, Switzerland.
authors.forename: U
authors.initials: U
authors.lastname: Sperling
authors.forename: F
authors.initials: F
authors.lastname: Franck
authors.forename: B
authors.initials: B
authors.lastname: van Cleve
authors.forename: G
authors.initials: G
authors.lastname: Frick
authors.forename: K
authors.initials: K
authors.lastname: Apel
authors.forename: G A
authors.initials: GA
authors.lastname: Armstrong
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D046911:Macromolecular Substances; D016296:Mutagenesis; D010088:Oxidoreductases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011521:Protochlorophyllide / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D046911:Macromolecular Substances; D010940:Plant Proteins; D012097:Repressor Proteins; D011521:Protochlorophyllide; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C023886:protochlorophyllide reductase; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases