<p>This work describes the regulation of drought stress responses in <i>Arabidopsis thaliana</i> and adresses the roles of the homeodomain-leucine zipper (HD-Zip) transcription factors in this regulation. The characteristics of <i>ATHB6</i> and <i>ATHB7</i>, two genes encoding class I HD-Zip transcription factors were analysed. </p><p>Expression of <i>ATHB6</i> and <i>ATHB7</i> was transcriptionally activated in plants subjected to water deficit or exogenous treatment with abscisic acid (ABA).</p><p>Transgenic plants constitutively expressing the <i>ATHB7</i> gene displayed a delayed elongation growth of the main inflorescence stem after transition to reproductive development. This phenotype is consistent with ATHB7 acting as a negative regulator of growth and development of the elongating stem in response to water availability.</p><p>Transgenic <i>abi1-1</i> mutant plants constitutively expressing the <i>ATHB7</i> gene displayed a reduced wiltiness as compared to monogenic <i>abi1-1</i> mutants. These data are consistent with the ATHB7 protein having a central role in the drought stress response, regulating the water balance of the plant, and acting downstream to <i>ABI1</i>. Furthermore, the data is consistent with ATHB7 acting as a positive regulator of the drought stress response.</p><p>The ABA-induced expression of the <i>ATHB7</i> gene displayed a dependence on the phytochrome system, suggesting an interplay between light and osmotic stress signaling in the regulation of the <i>ATHB7</i> gene.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-1857 |
| Date | January 2002 |
| Creators | Hjellström, Mattias |
| Publisher | Uppsala University, Physiological Botany, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1104-232X ; 690 |
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