<p>In the present work the regulation of environmentally induced cell death and signaling of systemic acquired acclimation (SAA) in <i>Arabidopsis thaliana</i> is characterized. We used the <i>lesion simulating disease1</i> (<i>lsd1</i>) mutant as a model system that is deregulated in light acclimation and programmed cell death (PCD). In this system we identify that redox status controlling SAA and cell death is controlled by the genes <i>LSD1</i>, <i>EDS1</i>, <i>EIN2</i> and <i>PAD4</i> which regulate cellular homeostasis of salicylic acid (SA), ethylene (ET), auxin (IAA) and reactive oxygen species (ROS). Furthermore we propose that the roles of <i>LSD1</i> in light acclimation and in biotic stress are functionally linked. The influence of SA on plant growth, short-term acclimation to high light (HL), and on the redox homeostasis of <i>Arabidopsis</i> leaves was also assessed. SA impaired acclimation of wild-type plants to prolonged conditions of excess excitation energy (EEE). This indicates an essential role of SA in acclimation and regulation of cellular redox homeostasis. We also show that cell death in response to EEE is controlled by specific redox changes of photosynthetic electron transport carriers that normally regulate EEE acclimation. These redox changes cause production of ET that signals through the<i> EIN2 </i>gene and regulon. In the<i> lsd1</i> mutant, we found that propagation of cell death depends on the plant defence regulators <i>EDS1 </i>and <i>PAD4</i> operating upstream of ET production. We conclude that the balanced activities of <i>LSD1</i>, <i>EDS1</i>, <i>PAD4</i> and <i>EIN2 </i>regulate chloroplast dependent acclimatory and defence responses. Furthermore, we show that <i>Arabidopsis</i> hypocotyls form lysigenous aerenchyma in response to hypoxia and that this process involves H<sub>2</sub>O<sub>2</sub> and ET signalling. We found that formation of lysigenous aerenchyma depends on <i>LSD1</i>, <i>EDS1</i> and <i>PAD4</i>. Conclusively we show that <i>LSD1</i>, <i>EDS1</i> and <i>PAD4</i>, in their functions as major plant redox and hormone regulators provide a basis for fundamental plant survival in natural contitions.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:su-1358 |
| Date | January 2006 |
| Creators | Mühlenbock, Per |
| Publisher | Stockholm University, Department of Botany, Stockholm : Botaniska institutionen |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
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