Luis A. del Río - Böcker

Oxygen (O ) appeared in significant amounts in the Earth’s atmosphere over 2. 2 2 billion years ago, largely due to the evolution of photosynthesis by cyanobacteria (Halliwell 2006). The O molecule is a free radical, as it has two impaired electrons 2 that have the same spin quantum number. This spin restriction makes O prefer to 2 accept its electrons one at a time, leading to the generation of the so-called reactive oxygen species (ROS). The chemical nature of these species dictates that they can create damage in cells. This has contributed to the creation of the “oxidative stress” concept; in this view, ROS are unavoidable toxic products of O metabolism and 2 aerobic organisms have evolved antioxidant defences to protect against this tox- ity (Halliwell 1981; Fridovich 1998). Indeed, even in present-day plants, which are full of antioxidants, much of the protein synthetic activity of chloroplasts is used to replace oxidatively damaged D1 and other proteins (Halliwell 2006). Yet, the use of the “oxidative stress” term implies that ROS exert their effects through indiscriminate widespread inactivation of cellular functions. In this context, ROS must not be able to react with lipids, proteins or nucleic acids in order to avoid any damage to vital cellular components. However, genetic evidence has suggested that, in planta, purely physicoche- cal damage may be more limited than previously thought (Foyer and Noctor 2005).

Oxygen (O ) appeared in significant amounts in the Earth’s atmosphere over 2. 2 2 billion years ago, largely due to the evolution of photosynthesis by cyanobacteria (Halliwell 2006). The O molecule is a free radical, as it has two impaired electrons 2 that have the same spin quantum number. This spin restriction makes O prefer to 2 accept its electrons one at a time, leading to the generation of the so-called reactive oxygen species (ROS). The chemical nature of these species dictates that they can create damage in cells. This has contributed to the creation of the “oxidative stress” concept; in this view, ROS are unavoidable toxic products of O metabolism and 2 aerobic organisms have evolved antioxidant defences to protect against this tox- ity (Halliwell 1981; Fridovich 1998). Indeed, even in present-day plants, which are full of antioxidants, much of the protein synthetic activity of chloroplasts is used to replace oxidatively damaged D1 and other proteins (Halliwell 2006). Yet, the use of the “oxidative stress” term implies that ROS exert their effects through indiscriminate widespread inactivation of cellular functions. In this context, ROS must not be able to react with lipids, proteins or nucleic acids in order to avoid any damage to vital cellular components. However, genetic evidence has suggested that, in planta, purely physicoche- cal damage may be more limited than previously thought (Foyer and Noctor 2005).

Peroxisomes are a class of ubiquitous and dynamic single membrane-bounded cell organelles, devoid of DNA, with an essentially oxidative type of metabolism. In recent years it has become increasingly clear that peroxisomes are involved in a range of important cellular functions in almost all eukaryotic cells. In higher eukaryotes, including humans, peroxisomes catalyze ether phospholipids biosynthesis, fatty acid alpha-oxidation, glyoxylate detoxification, etc, and in humans peroxisomes are associated with several important genetic diseases. In plants, peroxisomes carry out the fatty acid beta-oxidation, photorespiration, metabolism of ROS, RNS and RSS, photomorphogenesis, biosynthesis of phytohormones, senescence, and defence against pathogens and herbivores. In recent years it has been postulated a possible contribution of peroxisomes to cellular signaling. In this volume an updated view of the capacity and function of peroxisomes from human, animal, fungal and plant origin as cell generators of different signal molecules involved in distinct processes of high physiological importance is presented.

Peroxisomes are a class of ubiquitous and dynamic single membrane-bounded cell organelles, devoid of DNA, with an essentially oxidative type of metabolism. In recent years it has become increasingly clear that peroxisomes are involved in a range of important cellular functions in almost all eukaryotic cells. In higher eukaryotes, including humans, peroxisomes catalyze ether phospholipids biosynthesis, fatty acid alpha-oxidation, glyoxylate detoxification, etc, and in humans peroxisomes are associated with several important genetic diseases. In plants, peroxisomes carry out the fatty acid beta-oxidation, photorespiration, metabolism of ROS, RNS and RSS, photomorphogenesis, biosynthesis of phytohormones, senescence, and defence against pathogens and herbivores. In recent years it has been postulated a possible contribution of peroxisomes to cellular signaling. In this volume an updated view of the capacity and function of peroxisomes from human, animal, fungal and plant origin as cell generators of different signal molecules involved in distinct processes of high physiological importance is presented.

Del Río’s research group focuses on the metabolism of reactive oxygen species (ROS), reactive nitrogen species (RNS) and antioxidants in plant peroxisomes, and the ROS- and RNS-dependent role of peroxisomes in plant cell signalling.