| Abstract Detail
Organelle Biology Kluth, Jantjeline [1], Gebert, Marina [2], Kruse, Karoline [2], Melonek, Joanna [3], Krupinska, Karin [3], Wienand, Udo [2], Lorbiecke, René [2]. The ETCHED1-orthologous AtZR1 protein is essential for plastid differentiation and plant development in Arabidopsis. In maize, loss of the ETCHED1 (ET1) protein results in impaired plastid development which leads to a pleiotropic mutant phenotype of kernels and seedlings. Moreover, transcriptional activity is significantly reduced in mutant chloroplasts. The Et1 gene was cloned in a forward genetic approach utilizing transposon tagging. Et1 encodes a plastid-targeted protein that possesses similarity to the nuclear transcription elongation factor TFIIS. ET1 is associated with the transcriptionally active chromosome (TAC) of plastids. Hence a function of ET1 in plastid transcript elongation is assumed. Similarity search identified a single Et1-homologous gene in Arabidopsis thaliana: AtZr1.
GFP fusion studies showed a co-localization of AtZR1 with plastid DNA. AtZr1-promoter:GUS studies revealed a particular expression of the AtZR1 gene during late embryogenesis and early leaf development. The homozygous AtZr1 T-DNA knockout mutant showed profound phenotypic abnormalities during embryonic development leading to lethality on soil. Still, plants could be recovered on MS medium supplemented with sucrose. These plants exhibited a pleiotropic phenotype with a severely altered habitus and defects in cellular organization, cell size and chloroplast development. Transcriptome analysis using microarrays revealed that 46% of the expressed chloroplast targeted genes are differentially regulated in the AtZr1-KO as compared to the wild type.
Although the AtZr1-KO phenotype is much more pronounced than that of the et1 mutant, the ectopic expression of the maize Et1 gene in the Arabidopsis AtZr1-KO fully complemented the mutant phenotype. Our experiments prove that both genes are functional orthologs. On the basis of these results the necessity of AtZR1 for chloroplast biology will be discussed.
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1 - Universität Hamburg, Biozentrum Klein Flottbek, Ohnhorststr. 18, Hamburg, 22609, Germany
2 - Universität Hamburg, Biozentrum Klein Flottbek
3 - Universität zu Kiel, Botanisches Institut
Keywords:
chloroplast development
pleiotropic mutant
chloroplast transcription
microarray.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P18004
Abstract ID:155 |
