Auxin plays an essential role in plant development. However, only a few genes related to auxin synthesis have been isolated and characterized in plants. Here, we show that the TRANSPORT INHIBITOR RESPONSE2 (TIR2) gene, required for auxin synthesis, has an important role in many growth processes. The TIR2 gene encodes a protein structurally related to aminotransferases. A tryptophan (Trp) aminotransferase has been proposed to convert Trp to indole-3-pyruvic acid (IPA), a precursor of auxin. The tir2 mutant is hypersensitive to 5-methyl-tryptophan (5-MT), an inhibitor of Trp synthesis and aminooxyacetate (AOA), an aminotransferase inhibitor. The TIR2 protein is localized at sites of auxin production. Treatment with IPA and indole-3-acetic acid (IAA) rescues the tir2 short-hypocotyl phenotype. These data suggest that the TIR2 protein functions as a Trp aminotransferase. I show that auxin negatively regulates expression of the TIR2 gene via the auxin signaling pathway suggesting that plants control auxin concentration by changing expression levels of auxin synthesis genes. Furthermore, I show that high temperature positively regulates expression of the TIR2 gene suggesting that high temperature controls auxin concentration by regulating auxin synthesis genes. This response does not appear to require the auxin-signaling pathway. Finally, I show evidence that auxin synthesized by TIR2 is essential for root meristem development.
|Commitee:||Hangarter, Roger, Innes, Roger, Kumar, Justin|
|Department:||Molecular, Cellular, and Developmental Biology|
|School Location:||United States -- Indiana|
|Source:||DAI-B 69/12, Dissertation Abstracts International|
|Subjects:||Molecular biology, Genetics, Plant biology|
|Keywords:||Arabidopsis, Auxin, Auxin synthesis, Root meristem, TIR2, Trp aminotransferase|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be