title: The Etched1 gene of Zea mays (L.) encodes a zinc ribbon protein that belongs to the transcriptionally active chromosome (TAC) of plastids and is similar to the transcription factor TFIIS.
abstract: Etched1 (et1) is a pleiotropic, recessive mutation of maize that causes fissured and cracked mature kernels and virescent seedlings. Microscopic examinations of the et1 phenotype revealed an aberrant plastid development in mutant kernels and mutant leaves. Here, we report on the cloning of the et1 gene by transposon tagging, the localization of the gene product in chloroplasts, and its putative function in the plastid transcriptional apparatus. Several alleles of Mutator (Mu)-induced et1 mutants, the et1-reference (et1-R) mutant, and Et1 wild-type were cloned and analyzed at the molecular level. Northern analyses with wild-type plants revealed that Et1 transcripts are present in kernels, leaves, and other types of tissue, and no Et1 expression could be detected in the et1 mutants analyzed. The ET1 protein is imported by chloroplasts and has been immunologically detected in transcriptionally active chromosome (TAC) fractions derived from chloroplasts. Accordingly, the relative transcriptional activity of TAC fractions was significantly reduced in chloroplasts of et1-R plants. ET1 is the first zinc ribbon (ZR) protein shown to be targeted to plastids. With regard to its localization and its striking structural similarity to the eukaryotic transcription elongation factor TFIIS, it is feasible that ET1 functions in plastid transcription elongation by reactivation of arrested RNA polymerases.
authors.affiliation: Institut für Allgemeine Botanik und Botanischer Garten, Universität Hamburg, Ohnhorststr. 18, D-22 609 Hamburg, Germany.
authors.forename: Oswaldo
authors.initials: O
authors.lastname: da Costa e Silva
authors.forename: René
authors.initials: R
authors.lastname: Lorbiecke
authors.forename: Preeti
authors.initials: P
authors.lastname: Garg
authors.forename: Lenard
authors.initials: L
authors.lastname: Müller
authors.forename: Martina
authors.initials: M
authors.lastname: Wassmann
authors.forename: Patricia
authors.initials: P
authors.lastname: Lauert
authors.forename: Mike
authors.initials: M
authors.lastname: Scanlon
authors.forename: An-Ping
authors.initials: AP
authors.lastname: Hsia
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Schnable
authors.forename: Karin
authors.initials: K
authors.lastname: Krupinska
authors.forename: Udo
authors.initials: U
authors.lastname: Wienand
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002875:Chromosomes; D018744:DNA, Plant / Q000032:analysis; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics*; D018087:Plastids / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D035602:Transcriptional Elongation Factors / Q000737:chemistry; D003313:Zea mays / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D010940:Plant Proteins; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; C018648:transcription factor S-II