Alternative splicing of the OsBWMK1 gene generates three transcript variants showing differential subcellular localizations

In eukaryotes, mitogen-activated protein kinases (MAPKs) play important roles in various developmental processes and in environmental stress responses. Here, we show that alternative splicing of the OsBWMK1, a member of the rice MAPK family, generates three transcript variants, OsBWMKIL, OsBWMKIM, and OsBWMKIS. The OsBWMKIL transcript variant was highly and constitutively expressed in all rice tissues tested and its expression was not altered by various stress conditions, whereas OsBWMKIM and OsBWMKIS were normally expressed at low levels but were induced by various stresses. A transient expression assay demonstrated that OsBWMKIL::GFP and OsBWMKIM::GFP were predominantly localized in the cytoplasm, whereas most OsBWMKIS::GFP was localized in the nucleus. Moreover, treatment with defense signaling related molecules, such as H2O2 and SA, induced translocation of OsBWMK1 isoforms from the cytoplasm to the nucleus. Thus, our results suggest that alternative splicing of OsBWMK1 generates three different transcript variants that produce proteins with different subcellular localizations. (c) 2007 Elsevier Inc. All rights reserved.