title: PPR8522 encodes a chloroplast-targeted pentatricopeptide repeat protein necessary for maize embryogenesis and vegetative development.
abstract: The pentatricopeptide repeat (PPR) domain is an RNA binding domain allowing members of the PPR superfamily to participate in post-transcriptional processing of organellar RNA. Loss of PPR8522 from maize (Zea mays) confers an embryo-specific (emb) phenotype. The emb8522 mutation was isolated in an active Mutator (Mu) population and co-segregation analysis revealed that it was tightly linked to a MuDR insertion in the first exon of PPR8522. Independent evidence that disruption of PPR8522 caused the emb phenotype was provided by fine mapping to a region of 116kb containing no other gene than PPR8522 and complementation of the emb8522 mutant by a PPR8522 cDNA. The deduced PPR8522 amino acid sequence of 832 amino acids contains 10 PPR repeats and a chloroplast target peptide, the function of which was experimentally demonstrated by transient expression in Nicotiana benthamiana. Whereas mutant endosperm is apparently normal, mutant embryos deviate from normal development as early as 3 days after pollination, are reduced in size, exhibit more or less severe morphological aberrations depending on the genetic background, and generally do not germinate. The emb8522 mutation is the first to associate the loss of a PPR gene with an embryo-lethal phenotype in maize. Analyses of mutant plantlets generated by embryo-rescue experiments indicate that emb8522 also affects vegetative plant growth and chloroplast development. The loss of chloroplast transcription dependent on plastid-encoded RNA polymerase is the likely cause for the lack of an organized thylakoid network and an albino, seedling-lethal phenotype.
authors.affiliation: Université de Lyon, Ecole Normale Supérieure de Lyon, Université Lyon 1, Unité Reproduction et Développement des Plantes, F-69364 Lyon,  France.
authors.forename: Davide
authors.initials: D
authors.lastname: Sosso
authors.forename: Matthieu
authors.initials: M
authors.lastname: Canut
authors.forename: Ghislaine
authors.initials: G
authors.lastname: Gendrot
authors.forename: Annick
authors.initials: A
authors.lastname: Dedieu
authors.forename: Pierre
authors.initials: P
authors.lastname: Chambrier
authors.forename: Alice
authors.initials: A
authors.lastname: Barkan
authors.forename: Gabriella
authors.initials: G
authors.lastname: Consonni
authors.forename: Peter M
authors.initials: PM
authors.lastname: Rogowsky
mesh_terms: D000595:Amino Acid Sequence; D002736:Chloroplasts / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D016415:Sequence Alignment; D003313:Zea mays / Q000196:embryology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D010940:Plant Proteins