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Molecular and Cellular Biology, November 2007, p. 7771-7780, Vol. 27, No. 22
0270-7306/07/$08.00+0 doi:10.1128/MCB.00429-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Institute for Integrative Genome Biology and Department of Botany and Plant Sciences, University of California, Riverside, California 92521,1 Research Centre for Vegetable Breeding, National Research Council, University of Naples, 80055 Portici, Italy,2 Department of Plant Sciences, University of Arizona, Tucson, Arizona 857213
Received 13 March 2007/ Returned for modification 24 May 2007/ Accepted 20 August 2007
SOS2, a class 3 sucrose-nonfermenting 1-related kinase, has emerged as an important mediator of salt stress response and stress signaling through its interactions with proteins involved in membrane transport and in regulation of stress responses. We have identified additional SOS2-interacting proteins that suggest a connection between SOS2 and reactive oxygen signaling. SOS2 was found to interact with the H2O2 signaling protein nucleoside diphosphate kinase 2 (NDPK2) and to inhibit its autophosphorylation activity. A sos2-2 ndpk2 double mutant was more salt sensitive than a sos2-2 single mutant, suggesting that NDPK2 and H2O2 are involved in salt resistance. However, the double mutant did not hyperaccumulate H2O2 in response to salt stress, suggesting that it is altered signaling rather than H2O2 toxicity alone that is responsible for the increased salt sensitivity of the sos2-2 ndpk2 double mutant. SOS2 was also found to interact with catalase 2 (CAT2) and CAT3, further connecting SOS2 to H2O2 metabolism and signaling. The interaction of SOS2 with both NDPK2 and CATs reveals a point of cross talk between salt stress response and other signaling factors including H2O2.
Published ahead of print on 4 September 2007.
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