Nuclear localization of the Arabidopsis blue light receptor cryptochrome 2

The cryptochrome blue light photoreceptor family of Arabidopsis thaliana co nsists of two members, CRY1 and CRY2 (PHH1). CRY2 contains a putative nucle ar localization signal (NLS) within its C-terminal region. We examined whet her CRY2 is localized in the nucleus and whether the C-terminal region of C RY2 is involved in nuclear targeting. Total cellular and nuclear protein ex tracts from Arabidopsis were subjected to immunoblot analysis with CRY2-spe cific antibodies. Strong CRY2 signals were obtained in the nuclear fraction . Fusion proteins consisting of the green fluorescent protein (GFP) and dif ferent fragments of CRY2 were expressed in parsley protoplasts and the loca lization of the fusion proteins was determined by fluorescence and confocal laser scanning microscopy. GFP-fusions containing the entire CRY2 protein or its C-terminal region were found exclusively in the nucleus. We conclude from these results that CRY2 is localized in the nucleus and that nuclear localization is mediated by the C-terminal region of CRY2.