Characterization of genes involved in the regulation of programmed cell death in Arabidopsis thaliana

PhD ceremony: Mr. M.K. Qureshi, 12.45 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Characterization of genes involved in the regulation of programmed cell death in Arabidopsis thaliana

Promotor(s): prof. J. Hille

Faculty: Mathematics and Natural Sciences

The aim of the research of Karam Qureshi was a characterization of genes involved in the regulation of programmed cell death (PCD) in the model plant Arabidopsis thaliana. PCD is an integral part in the life cycle of multicellular organisms. It is the elimination of unwanted or severely damaged cells. In plants, it is involved in growth, development and in maintaining tissue homeostasis. PCD is also triggered by abiotic and biotic stresses such as ozone, ultraviolet light, drought, extreme temperatures, herbicides and by pathogen attack. One such fungal pathogen, Alternaria alternata f. sp. lycopersici, secretes host-specific phytotoxins (AAL-toxins) prior to the onset of cell death. These abiotic and biotic stresses induce reactive oxygen species (ROS) during PCD. ROS is the collective term used for singlet oxygen, superoxide radical, hydroxyl radical and hydrogen peroxide. The aim of this research is a characterization of genes involved in the regulation of PCD in the model plant Arabidopsis thaliana.

PCD is a complex and genetically controlled process. Both AAL-toxins and ROS act as signaling molecules initiating the induction and execution of the PCD cascade in plants. These molecules trigger a massive reprogramming at the transcriptional level. The role of early regulated genes during ROS and AAL-toxins induced PCD was studied by Qureshi. Additionally, he isolated and characterized genes with a potential role in ROS and AAL-toxins induced PCD. He demonstrated that mutations in these genes confer tolerance to ROS- and AAL-toxins-sensitive mutants, indicating a relation between AAL-toxins and ROS during PCD.

The identification of regulators is important for understanding the complex PCD pathway. In addition, these regulators can be helpful in understanding plant defense mechanisms against pathogen attack and accumulation of ROS induced by external stimuli.