S60 Abstracts / Comparative Biochemistry and Physiology, Part A 146 (2007) S53–S62

signalling pathway, and the role of oxidative stress in mediatingits effects upon ageing.

doi:10.1016/j.cbpa.2007.01.052

CSS.21The perception of reactive oxygen species in plants: The

road to signal transduction

J. Hancock, J. Bright, J. Harrison, M. Ladomery, T. Askari, S.Neill, (UWE, Bristol, United Kingdom); R. Desikan, (ImperialCollege London, United Kingdom)

During normal life, substantial amounts of reactive oxygenspecies (ROS) are produced by organisms, and this is thought tocontribute to the ageing process. ROS are likely to cause damageto a variety of bio-molecules, and such damage can lead tocellular dysfunction and disease, but could also be used tocontrol programmed death, ie apoptosis. However, ROS are alsoknown to control a wide variety of cellular activities, such asdevelopment and stomatal closure, and such control will not bethrough random oxidative damage. To activate a signaltransduction cascade, the first event must be the perception ofthe ROS, followed by the activation or inhibition of thedownstream signalling components, to bring about the desiredeffect. ROS perception may involve the oxidation of thiol groupson cysteines on proteins, with these proteins being at the head ofsignalling cascades. Such thiols are also likely to be targets fornitric oxide, adding a possible level of complexity to signalling.Therefore, proteins with susceptible thiols need to be identified.Using fluorescence tagging in conjunction with mass spectro-metric identification, several such proteins have been identifiedin Arabidopsis thaliana, including glyceraldehyde 3-phosphatedehydrogenase (GAPDH), a protein already characterised fromanimal cells as being controlled by ROS. The challenge now is todetermine exactly how ROS affects the functioning of suchproteins in cell signalling pathways, to determine thoseresponses specifically downstream of these proteins, and toelucidate how such signalling controls the survival, or death, ofcells.

doi:10.1016/j.cbpa.2007.01.053

CSS.22Genetic, molecular and physiological mechanismscontrolling cell death, defenses, and antioxidant network inresponse to abiotic and biotic stresses in plants

S. Karpinski, (Stockholm University, Sweden, Polish Academyof Sciences, Poland); P. Muhlenbock, (Stockholm University,Sweden)

Molecular, genetic and physiological mechanisms of cellularresponses, such as cell death, signaling of systemic acquired

acclimation (SAA) and systemic acquired resistance (SAR), inresponse to environmentally induced oxidative stress in plantswill be discussed. We identify that the redox status of theplastoquinone pool that signalizes in both, light acclimation andcell death responses, is controlled by LSD1, EDS1, EIN2 andPAD4. We also show that these genes regulate not only cellularhomeostasis of salicylic acid (SA) and superoxide ion, but alsoethylene (ET), auxin (IAA), and other reactive oxygen species(ROS). Furthermore we propose that the roles of LSD1 in lightacclimation and in restricting pathogen-induced cell death arefunctionally linked. Through its regulation, LSD1 influencesthe effectiveness of photorespiration in dissipating excessexcitation energy (EEE). The influence of SA on plant growth,on acclimation to EEE, and on the cellular redox homeostasis ofArabidopsis thaliana leaves is also assessed. These observa-tions implied an essential role of SA in the light acclimationprocesses and in regulating the redox homeostasis of the cell.We also find that propagation of cell death depends on the plantdefence regulators EDS1 and PAD4 operating upstream of ETproduction. Finally, we show that Arabidopsis hypocotyls formlysigenous aerenchyma in response to hypoxia and that thisprocess involves H2O2 and ETsignalling, which is controlled byLSD1, EDS1 and PAD4 operating downstream of metabolicsignals. We conclude that the balanced activities of LSD1,EDS1, PAD4 and EIN2 regulate chloroplast dependentacclimatory and defence responses.

doi:10.1016/j.cbpa.2007.01.054

CSS.23Synthesis of novel nitrone spin-traps for the investigation ofoxidative stress

C. Quin, R. Hartley, (University of Glasgow, Scotland)

Reactive oxygen species such as superoxide and hydroxylradicals are natural side products of the respiratory cycle andare terminated by our inherent antioxidant defence system.However, during periods of oxidative stress the body's pro-oxidant activity exceeds its antioxidant activity leading to anexcess of ROS.These radicals can react with a variety of biomolecules includingDNA, proteins and lipids. The damage caused can lead to cellmalfunction and ultimately apoptosis. They are mainly producedin the electron transport chain located in the inner membrane ofmitochondria and are therefore thought to be the major cause ofmitochondrial dysfunction. It is hypothesised that the accumu-lative damage occuring, over time especially to the mitochon-dria, is a major contributor to a variety of age related diseases aswell as the degenerative effects of ageing.Due to the short half-life of ROS they cannot be directlyanalysed by Electron Paramagnetic Resonance (EPR) Spectro-scopy and therefore a technique known as spin-trapping isemployed. Novel mitochondrial spin-traps have been synthe-sised and their ability to trap oxygen-centred and carbon-centred