Molecular mechanisms of stress tolerance in plants
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Environmental stress conditions such as drought, salt stress and pathogenic fungi affect negatively plant growth and productivity. Therefore, it is necessary to search for new genetic components and strategies for improving resistance and tolerance in crops. In the present thesis, we describe two different approaches that increase our understanding of mechanisms of stress tolerance in plants. The first approach is to study an extreme adaptation to dehydration tolerance from a plant than can "resurrect" after being completely dried. The second study addresses how plant might respond to two different stresses simultaneously, and how one stress can enhance the response to the other. In Chapter 2, we investigate the dehydration tolerance mechanism in the model resurrection grass species Sporobolus stapfianus using a large scale expression profiling of leaf tissues at full hydration, during drying and after re-watering. This study provides some important insights into the gene regulatory mechanisms used by this interesting plant during severe vegetative desiccation and subsequent recovering during re-watering. We also found some genes that are differentially expressed between S. stapfianus and its desiccation sensitive sister species S. pyramidalis. These genes are considered potential candidates for engineering drought tolerant crops. Previous studies have shown a positive effect of chitin (released from the fungal cell wall) on salinity tolerance. In Chapter 3, we explore the cross talk between salt stress and chitin-triggered immune responses. Our results demonstrate a physiological and biochemical link between salinity stress and chitin-triggered innate immunity. Chitin receptors, CERK1 and LYK4, and ANN1, a NaCl- induced calcium permeable channel, interact physically at the plasma membrane and are necessary to modulate early responses (e.g. Ca2+ signaling) to both stresses. Understanding these layers of cross-talk may lead to more sustainable methods to employ innate immunity to protect against both biotic and abiotic stress induced crop losses.