Wu, Guosheng , Spalding, Edgar .
The Effect of Different Subcellular Targeting of Cryptochrome 1 on Blue Light Regulated Photomorphogenesis.
Cryptochrome 1 (CRY1) is a blue light receptor mediating plant photomorphogenesis. In seedlings, CRY1 is required for blue-light-induced membrane depolarization, inhibition of hypocotyl elongation, cotyledon expansion, inhibition of petiole elongation, and promotion of root elongation. The CRY1 protein is found in the nucleus and also in the cytoplasm of cells, but which pool is more important for function has not been strictly tested. We used nuclear localization signals (NLS) or nuclear export signals (NES) to control the subcellular localization of GFP-tagged forms of CRY1 in order to address the issue of functional location. The 35S promoter drove expression of all constructs in a cry1 mutant background. Microscopy confirmed that the NES signal restricted CRY1 to the cytoplasm and NLS restricted it to the nucleus. For control purposes, plants overexpressing GFP-CRY1 with no targeting signal were created. GFP-NLS-CRY1 seedlings were hypersensitive to blue light with respect to hypocotyl and petiole growth inhibition, and GFP-NES-CRY1 seedlings were indistinguishable from the cry1 mutant, indicating nuclear CRY1 was key. The blue-light-induced membrane depolarization, which plays a role in hypocotyl growth suppression, was rescued by nuclear-localized CRY1 but not by GFP-NES-CRY1, consistent with the growth results. However, cotyledon expansion and primary root growth enhancement were rescued by GFP-NES-CRY1 and not by GFP-NLS-CRY1. A nonfunctional missense mutant form of cry1 did not rescue the root or cotyledon phenotypes when expressed in the cytoplasm, indicating CRY1 functions in the cytoplasm to exert these photomorphogenic effects. Thus, nuclear and cytoplasmic CRY1 contribute to different aspects of blue light-induced photomorphogenesis of seedlings.
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1 - University of Wisconsin, Department of Botany, 430 Lincoln Drive, Birge Hall/B132, Madison, WI, 53706, USA
2 - University of Wisconsin, Department of Botany
Presentation Type: ASPB Minisymposium
Location: Continental C/Hilton
Date: Wednesday, July 11th, 2007
Time: 9:20 AM