This paper is in the current issue of Nature (27 March), 452, 487-491; 2008.. Because I either cannot or haven’t worked out how to append PDFs to Network posts, I have appended a PDF at this Nautilus post, for journal club members who don’t have access to Nature’s full content (abstracts are free to access online). The abstract is below. I look forward to reading what people make of this paper: it has its share of acronym disease (acronymitis, I call it), but I found the abstract remarkably clear.

SLAC1 is required for plant guard cell S-type anion channel function in stomatal signalling
Triin Vahisalu1,2,6, Hannes Kollist1,3,6, Yong-Fei Wang4,6, Noriyuki Nishimura4, Wai-Yin Chan4, Gabriel Valerio4, Airi Lamminmäki1, Mikael Brosché1, Heino Moldau3, Radhika Desikan5,7, Julian I. Schroeder4 & Jaakko Kangasjärvi1

Plant Biology, Department of Biological and Environmental Sciences, University of Helsinki, FI-00014 Helsinki, Finland
Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Tartu 51005, Estonia
Institute of Technology, University of Tartu, Tartu 50411, Estonia
Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla, California 92093-0116, USA
Centre for Research in Plant Science, University of the West of England, Bristol BS16 1QY, UK
These authors contributed equally to this work
Present address: Division of Biology, Imperial College London, London SW7 2AZ, UK.
Correspondence to: Jaakko Kangasjärvi1 Correspondence and requests for materials should be addressed to J.K. (Email: jaakko.kangasjarvi@helsinki.fi).

Stomatal pores, formed by two surrounding guard cells in the epidermis of plant leaves, allow influx of atmospheric carbon dioxide in exchange for transpirational water loss. Stomata also restrict the entry of ozone — an important air pollutant that has an increasingly negative impact on crop yields, and thus global carbon fixation1 and climate change2. The aperture of stomatal pores is regulated by the transport of osmotically active ions and metabolites across guard cell membranes3, 4. Despite the vital role of guard cells in controlling plant water loss3, 4, ozone sensitivity1, 2 and CO2 supply2, 5, 6, 7, the genes encoding some of the main regulators of stomatal movements remain unknown. It has been proposed that guard cell anion channels function as important regulators of stomatal closure and are essential in mediating stomatal responses to physiological and stress stimuli3, 4, 8. However, the genes encoding membrane proteins that mediate guard cell anion efflux have not yet been identified. Here we report the mapping and characterization of an ozone-sensitive Arabidopsis thaliana mutant, slac1. We show that SLAC1 (SLOW ANION CHANNEL-ASSOCIATED 1) is preferentially expressed in guard cells and encodes a distant homologue of fungal and bacterial dicarboxylate/malic acid transport proteins. The plasma membrane protein SLAC1 is essential for stomatal closure in response to CO2, abscisic acid, ozone, light/dark transitions, humidity change, calcium ions, hydrogen peroxide and nitric oxide. Mutations in SLAC1 impair slow (S-type) anion channel currents that are activated by cytosolic Ca2+ and abscisic acid, but do not affect rapid (R-type) anion channel currents or Ca2+ channel function. A low homology of SLAC1 to bacterial and fungal organic acid transport proteins, and the permeability of S-type anion channels to malate9 suggest a vital role for SLAC1 in the function of S-type anion channels.