Brown, Bobby A. , Cloix, Catherine , Headland, Lauren R. , Herzyk, Pawel , Kaiserli, Eirini , Jenkins, Gareth I. .
UV-B Signalling Pathways in Arabidopsis: UVR8 Defines a Photomorphogenic Pathway that Regulates Transcription.
Plants use different wavelengths of light as specific triggers for various morphological and developmental responses. UV-B wavelengths (280-320 nm) of sunlight can cause molecular damage within the plant at high fluence rates but at low fluence rates they act as an informational signal. Thus in Arabidopsis while UV-B can generate reactive oxygen species (ROS) and damage the photosynthetic apparatus, membrane systems and DNA, it also stimulates photomorphogenesis and flavonoid biosynthesis. One pathway that mediates responses specific to UV-B and stimulates the expression of UV-protective genes involves Arabidopsis UV RESISTANCE LOCUS 8 (UVR8) and the transcription factor HY5. The UVR8 polypeptide shares 50 % sequence similarity with the RCC1 family of proteins found in a variety of eukaryotes. These are indispensable guanine nucleotide exchange factors (GEFs) and are required to regulate the cell cycle, mitosis and transport across the nuclear membrane. However, in Arabidopsis uvr8 mutants are indistinguishable from wild-type under normal growth conditions and the UVR8 protein has very little GEF activity suggesting a novel role for UVR8 in plants. We demonstrated a direct interaction between UVR8 and a chromatin fragment containing the HY5 promoter and reported that UVR8 defines a new photomorphogenic signalling pathway in plants that orchestrates UV protection (Brown et al., 2005, PNAS 102, 18225-30). Recently we have defined the role of the HYH transcription factor in this pathway. Furthermore, we have identified a second pathway that operates independently of UVR8, HY5 and HYH, and regulates a separate set of genes. Neither of these UV-B pathways requires the phytochromes, cryptochromes or phototropins and each has a different fluence rate response profile.
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1 - University of Glasgow, Institute of Biomedical and Life Sciences, Plant Science Group, Division of Biochemistry and Molecular Biology, Glasgow, G12 8QQ, UK
2 - University of Glasgow, Institute of Biomedical and Life Sciences
UV RESISTANCE LOCUS 8.
Presentation Type: ASPB Minisymposium
Location: Continental C/Hilton
Date: Wednesday, July 11th, 2007
Time: 9:45 AM