UV-B promotes rapid nuclear translocation of the Arabidopsis UV-B specific signaling component UVR8 and activates its function in the nucleus.
Arabidopsis thaliana UV RESISTANCE LOCUS8 (UVR8) is a UV-B-specific signaling component that binds to chromatin and regulates UV protection by orchestrating expression of a range of genes. Here, we studied how UV-B regulates UVR8. We show that UV-B stimulates the nuclear accumulation of both a green fluorescent protein (GFP)-UVR8 fusion and native UVR8. Nuclear accumulation leads to UV-B induction of the HY5 gene, encoding a key transcriptional effector of the UVR8 pathway. Nuclear accumulation of UVR8 is specific to UV-B, occurs at low fluence rates, and is observed within 5 min of UV-B exposure. Attachment of a nuclear export signal (NES) to GFP-UVR8 causes cytosolic localization in the absence of UV-B. However, UV-B promotes rapid nuclear accumulation of NES-GFP-UVR8, indicating a concerted mechanism for nuclear translocation. UVR8 lacking the N-terminal 23 amino acids is impaired in nuclear translocation. Attachment of a nuclear localization signal (NLS) to UVR8 causes constitutive nuclear localization. However, NLS-GFP-UVR8 only confers HY5 gene expression following UV-B illumination, indicating that nuclear localization, although necessary for UVR8 function, is insufficient to cause expression of target genes; UV-B is additionally required to stimulate UVR8 function in the nucleus. These findings provide new insights into the mechanisms through which UV-B regulates gene expression in plants.
Kaiserli
Eirini
E
Plant Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Jenkins
Gareth I
GI
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism* / Q000528:radiation effects*; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007700:Kinetics; D008027:Light; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D049790:Nuclear Export Signals; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D021381:Protein Transport / Q000528:radiation effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014466:Ultraviolet Rays
D029681:Arabidopsis Proteins; D002868:Chromosomal Proteins, Non-Histone; D049790:Nuclear Export Signals; D011993:Recombinant Fusion Proteins; C525052:Uvr8 protein, Arabidopsis; D049452:Green Fluorescent Proteins