Molecular genetic analysis of programmed cell death

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Programmed cell death (PCD) is a physiological process that is part of the life of all organisms. In plants and animals, PCD is essential for normal development and for the removal of damaged or infected cells. Different types of PCD have been described in plant cells in response to developmental cues, pathogen infection or abiotic stresses. One example of PCD may occur on infected leaves at the site of pathogen entry (the so-called "hypersensitive response") to limit pathogen spread. This response is generally associated with the induction of a specific disease resistance mechanism in the plants.         In this research program, the early events and proteins involved in the activation and regulation of cell death and cell survival pathways will be characterized in the plant model Arabidopsis thaliana. A unique genetic approach will be used to identify key regulators in the control of PCD induced by UV-C irradiation. This information will be useful to understand how cell survival may be favoured in some types of plant defence reactions and could then be applied to the development of symptom-less resistant plants.     A second approach studies the PCD-inducing activity of a phytotoxin, thaxtomin A (TA), that is essential for the development of common scab disease of potato. We have shown that TA activates PCD through inhibition of cellulose biosynthesis in Arabidopsis cell suspensions. We will examine the effect of TA in whole plants and characterize the early signals that activate this process of cell death. Moreover, we have produced plant cell suspensions that can grow in the presence of lethal concentrations of TA. Changes in gene expression in these cells will be analysed to determine how these cells can survive to TA. We think this data will lead to the development of plants that are more tolerant to stresses perturbing the plant cell wall, such as TA, wounding and pathogen infection.