Aluminium toxicity is the main limiting factor in crop production on acid soils. The main symptom of aluminium toxicity is a rapid inhibition of root growth, but the mechanism of root growth cessation remains unclear. In this diploma thesis we deal with the question of whether phospholipases PLDα1 and PLDδ may play a role in the mechanism of aluminium toxicity. We compared the responses of plants lacking PLDα and PLDδ with WT plants. Growth analysis of roots was performed in hydroponic conditions. The most sensitive part of roots was transient zone in which cells were dying earlier. It was further found that pldα1 plants were less sensitive on aluminium toxicity because their roots showed less growth inhibition than WT. Pldδ plants did not differ from WT plants in their response to aluminum. During further analysis of the pldα1 reactions, it was found that the root cells were capable of cell expansion during aluminum toxicity, and the cellular malformations were formed on the roots. This phenomenon was associated with faster reorientation and even depolymerization of cortical microtubules in response to toxic aluminium in pldα plants compared to WT plants. The results indicated that PLDα1 molecule affects the stability of cortical microtubules. Microtubules were less stable and they depolymerized...

Plants are in a perpetual evolutionary arms race with a wide range of pathogens. Their sessile nature has led plants to evolve defense mechanisms that can quickly recognize a unique stressor and deploy a resistance tailored for a specific attack. The salicylic acid (SA) mediated defense pathway has been shown to be one of the major defense tactics plants can initiate to defend themselves against microbial pathogens. Following a pathogen attack high levels of methyl salicylate (MeSA) are produced that can be converted to SA by the enzyme salicylic acid binding protein 2 (SABP2). A yeast two-hybrid screening was performed to identify protein interactions with SABP2 to better understand the regulation of the enzyme on a cellular level. SBIP-436 is an interacting protein of tobacco SABP2 which showed high homology to phospholipase D-δ (PLD- δ). With an abundance of stimulators PLD- δ may be a lipid signaling modulator developed to perform various functions in different situations. PLD- δ may be a key player in a lipid signaling cascade in the SA mediated defense pathway. We present a novel Nicotiana tabacum PLD- δ putative gene construct. We demonstrate that the putative PLD- δ is subject to alternative splicing and its expression is differentially modulated under biotic and abiotic stress. Our results indicate that this putative PLD- δ may play a role in the SA mediated defense pathway.