title: Substrate-dependent and organ-specific chloroplast protein import in planta.
abstract: The NADPH-dependent protochlorophyllide (Pchlide) oxidoreductase (POR) is unique because it is a photoenzyme that requires light for its catalytic activity and uses Pchlide itself as a photoreceptor. In Arabidopsis, there are three structurally related PORs, denoted PORA, PORB, and PORC. The import of one of them, PORA, into plastids of cotyledons is substrate dependent. This substrate dependence is demonstrated in intact seedlings of wild-type Arabidopsis and two mutants, xantha2, which is devoid of Pchlide, and flu, which upon redarkening rapidly accumulates Pchlide. In true leaves, PORA uptake does not require the presence of Pchlide. The organ specificity of the substrate-dependent import of PORA reveals a means of controlling plastid protein translocation that is closely associated with a key step in plant development, the light-dependent transformation of cotyledons from a storage organ to a photosynthetically active leaf.
authors.affiliation: Institute of Plant Sciences, Plant Genetics, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland.
authors.forename: Chanhong
authors.initials: C
authors.lastname: Kim
authors.forename: Klaus
authors.initials: K
authors.lastname: Apel
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism* / Q000528:radiation effects; D018548:Cotyledon / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D018507:Gene Expression Regulation, Developmental / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D049452:Green Fluorescent Proteins; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008027:Light; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000528:radiation effects; D011521:Protochlorophyllide / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; C478633:FLU protein, Arabidopsis; D007527:Isoenzymes; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D011521:Protochlorophyllide; D044925:Oxidoreductases Acting on CH-CH Group Donors; C023886:protochlorophyllide reductase