PT - JOURNAL ARTICLE AU - Liina Jakobson AU - Lauri Vaahtera AU - Kadri Tõldsepp AU - Maris Nuhkat AU - Cun Wang AU - Yuh-Shuh Wang AU - Hanna Hõrak AU - Ervin Valk AU - Priit Pechter AU - Yana Sindarovska AU - Jing Tang AU - Chuanlei Xiao AU - Yang Xu AU - Ulvi Gerst Talas AU - Maido Remm AU - Saijaliisa Kangasjärvi AU - M. Rob G. Roelfsema AU - Honghong Hu AU - Jaakko Kangasjärvi AU - Mart Loog AU - Julian I. Schroeder AU - Hannes Kollist AU - Mikael Brosché TI - Natural Variation in Arabidopsi<em>s</em> Cvi-0 Accession Uncovers Regulation of Guard Cell CO<sub>2</sub> Signaling by MPK12 AID - 10.1101/073015 DP - 2016 Jan 01 TA - bioRxiv PG - 073015 4099 - http://biorxiv.org/content/early/2016/09/01/073015.short 4100 - http://biorxiv.org/content/early/2016/09/01/073015.full AB - Plant gas exchange is regulated by guard cells that form stomatal pores. Stomatal adjustments are crucial for plant survival; they regulate uptake of CO2 for photosynthesis, loss of water and entrance of air pollutants such as ozone. We mapped ozone hypersensitivity, more open stomata and stomatal CO2-insensitivity phenotypes of the Arabidopsis thaliana accession Cvi-0 to a single amino acid substitution in MAP kinase 12 (MPK12). In parallel we showed that stomatal CO2-insensitivity phenotypes of a mutant cis (CO2-insensitive) were caused by a deletion of MPK12. Lack of MPK12 impaired bicarbonate-induced activation of S-type anion channels. We demonstrated that MPK12 interacted with the protein kinase HT1, a central node in guard cell CO2 signaling, and that MPK12 can function as an inhibitor of HT1. These data provide a new function for plant MPKs as protein kinase inhibitors and suggest a mechanism through which guard cell CO2 signaling controls plant water management.