TY  - GEN
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/13679/
ID  - heidok13679
KW  - RNS-Stabilität 
KW  -  EisenhomöostasePlant Physiology 
KW  -  Iron Homeostasis 
KW  -  RNA Stability 
KW  -  Arabidopsis thaliana 
KW  -  Anther development
N2  - The aim of this thesis was to functionally characterize the Cysteine Three Histidine 2 (CTH2)gene in the model plant Arabidopsis thaliana, which is a candidate for a role in plant iron homeostasis. AtCTH2 belongs to the family of tandem zinc-finger proteins (TZF) which are known to bind and initiate the degradation of mRNAs in other organisms. The closest homologue of AtCTH2 in yeast is negatively regulating the stability of a group of specific transcripts under iron-deficient conditions. Heterologous expression of an Arabidopsis CTH2 cDNA can complement a yeast cth1?cth2? mutant. Here it was shown that AtCTH2 partly co-localizes with a marker of plant stress-granules in Arabidopsis protoplasts. Localization to these sites of transcript degradation is an indication that CTH2 plays a role in post-transcriptional regulation of gene expression by influencing transcript stability. Two mutants carrying T-DNA insertions in CTH2 were identified and characterized. The two mutants showed different phenotypes, which was attributed to different partial CTH2 transcripts originating at the CTH2 locus. The results suggested that the partial transcript found in cth2-1 caused a dominant hypersensitivity to iron deficiency, and possibly represents a gain-of-function allele. Most affected were the youngest leaves, which showed a drastic reduction of chlorophyll concentrations and reduced growth, when compared to wild-type plants grown under the same conditions. The total content of iron in the youngest leaves was not affected by the cth2-1 mutation, which showed that long-distance iron reallocation under Fe-deficient conditions is not disturbed. The cth2-2 allele caused sporophytic male sterility, and is recessive. In homozygous cth2-2 plants tetrads of microspores are found, but instead of separating into individual microspores, the cells enlarged, showed granular structures, and eventually degenerated. In accordance with this, the activity of the CTH2 promoter was localized to the connective tissue during the release of microspores from tetrads. The developmental defect might be caused by a disturbed iron homeostasis, since iron content was lower in cth2-2 anthers then in wild-type anthers. A microarray analysis identified several candidate pathways and categories of genes, in which transcript levels are over-proportionately misregulated in cth2-2 anthers compared to wildtype anthers. In summary, it was shown that CTH2 has a role in Arabidopsis thaliana iron homeostasis and is critical for anther development. In both roles CTH2 is the first described RNA-binding protein in a plant to act in these roles.
A1  - Reuscher, Stefan
AV  - public
TI  - Functional characterization of the Arabidopsis thaliana gene Cysteine Three Histidine 2
Y1  - 2012///
ER  -