Physiologia Plantarum 138: 357–359. 2010 Copyright  Physiologia Plantarum 2010, ISSN 0031-9317 EDITORIAL Plant ROS and RNS: making plant science more radical than ever Michael Wrzaczek, Kirk Overmyer and Jaakko Kangasj ¨ arvi * Plant Biology Division, Department of Biosciences, University of Helsinki, Helsinki, Finland e-mail: jaakko.kangasjarvi@helsinki.fi doi:10.1111/j.1399-3054.2010.01359.x The Plant Oxygen Group (POG) is a group of plant researchers organized under the Society for Free Radical Research (SFRR) to promote research into reactive oxygen species (ROS) in plants. More recently research on the reactive nitrogen species (RNS, including nitric oxide and related molecules) has been included in the POG. This special issue of Physiologia Plantarum highlights the 10th meeting of the POG recently held in Helsinki, Finland July 8–10, 2009. More than 230 researchers from all parts of the world attended the conference, and spent the three intense and tightly packed days listening to lectures, discussing posters, striking up collaborations, hypothesizing and brainstorming. Now looking back to the meeting, we have time to reflect on the research area of ROS and RNS in plants, and how the Plant ROS meeting helps the research community. What was our starting point when the meetings were initiated and where are we going? Research on ROS in plants has a long and rich history. Much has happened since the discovery of superoxide and hydrogen peroxide production via the Mehler reaction in the photosystems (Mehler 1951). By the beginning of the 1990s, Barry Halliwell, Christine Foyer and Kozi Asada had already characterized the ascorbate- glutathione cycle (renamed as Halliwell–Foyer–Asada cycle on the occasion of the plant ROS meeting in Ghent, Belgium, in 2007; Halliwell and Foyer 1976, Hossain and Asada 1987). Scientists had also realized that pathogen infected plant tissues produce ROS (Doke 1983). The production of ROS in response to environmental stress was generally accepted and research focused on the role of scavengers controlling ROS damage (Bowler et al. 1989a, 1989b, 1991, Legendre et al. 1993, Tsang et al. 1991). A new picture of ROS, not only as damaging agents, but also as signaling intermediates began to emerge with roles in hormone signaling and the regulation of defense gene expression providing further links to pathogen defense (Chen et al. 1993). Many of the tools that we rely on today were already in development and much of our current research in plant ROS is based on the fundamentals that were laid down during this time. ROS were considered important molecules with broad functions in environmental stress. However, at this point, the breadth of processes involving ROS was yet to be expanded. Indeed, the role of ROS was rapidly expanding in all branches of the biological sciences. In spite of the large and active community of plant ROS researchers, it was difficult for the community to find a niche in the larger ROS field, which was so important in human medicine. This was essentially the situation when the first meeting on ROS in plants was organized by George AF Hendry from the Department of Animal and Plant Sciences of the University of Sheffield together with RMM Crawford and BA Goodman. The ‘First International Conference on the Role of Oxygen in Environmental Stress in Plants’ was held in St. Andrews (Scotland, UK) back in September 1993 and attracted more than 150 participants from all over the world, some of whom are still regular attendants at ROS meetings. This was the very beginning of the POG. The POG and the Plant ROS meetings were organized under the umbrella of the SFRR to give the researchers this common forum. The desire to share ideas through informal and relaxed exchange, strike up common projects and novel ideas, remains a motivation that is still alive and growing in today’s Plant ROS meetings, in which the roles of RNS, and the interaction of ROS and RNS have gained a rather significant portion. The plant ROS meeting and the SFRR have mutually increased their visibility in plant ROS research community. Increased interdisciplinary collaboration between the organizations within the Physiol. Plant. 138, 2010 357