Extracellular ATP and Suppression of Cell Death in Plants.

All living organisms have to be able to sense the environment they are in. The sensing mechanisms are important as they allow an organism to realise that they are in new conditions and have to adjust things accordingly. That not only applies to conditions such as a change in temperature but also to attack by other organisms and chemical compounds. Changes in conditions require a response so that the organism can survive. In order to get that response we first need to detect the change and then send a message to the nucleus of the cell to allow it to make appropriate responses. We have found that a major energy compound, ATP, which is classically found within cells is also present outside of cells. When this is removed the plants die. When fungi attack plants they bring about cell death. However the mechanism by which death is actually brought about is not always the same. The fungus Fusarium kills plant cells by secreting a toxin Fumonisin B1 [FB1], however if the ATP out side of the cell [extracellular] is kept high the cells do not die. This has led us to the conclusion that extracellular ATP is essential for cells to live. Signalling in living organisms is known to be mediated by proteins. In this study we aim to look for the proteins involved in sensing extracellular ATP involved with keeping plant cells alive.

We have discovered that extracellular ATP [EATP] is essential for plant cell viability and that its removal results in cell death. Additionally Fumonisin B1[FB1] mediated cell death can also be prevented by addition of extracellular ATP. In this study we aim to use a joint transcriptomic and proteomic approach to identify genes and proteins which are central to the suppression of cell death by EATP. We specifically aim to do the following: 1. Identify the subset of genes differentially expressed in response to FB1 whose response is attenuated by the addition of exogenous ATP. This will allow us to identify genes whose expression are potentially involved in preventing cell death. 2. Identify FB1-induced alterations in protein levels that are attenuated by the addition of exogenous ATP. This will allow us to identify proteins whose level is altered by the addition of exogenous ATP and are potentially involved in preventing cell death. 3. Identify ATP binding proteins in the ECM. These could be the primary targets for EATP. 4. Find the position at which ATP depletion participates in the cell death pathway relative to the major cell signalling pathways in plants. 5. Evaluate the importance and role of the components identified in 1, 2 and 3 using reverse genetics.