Identification of photoreceptors and signalling network(s) by which ultraviolet light modulates the circadian system in Arabidopsis thaliana
Final Report Abstract
Ultraviolet-B (UVB) light is a natural and dynamic component of sunlight and it affects plant growth and development in many ways. Longtime exposure to high-intensity UVB is detrimental, since it causes DNA damage, protein cross-linking and destruction of membranes. However, recent discoveries that led to the identification of the first UVB-specific receptor, UVR8, demonstrated that UVB irradiation is also interpreted by plants as a specific photomorphogenic signal. Accordingly, it has been firmly established by whole genome transcriptome analysis that UVB-induced physiological responses are mediated by different signaling cascades. Here we report that (i) UVB-induced transcription of UVR8-dependent (HY5) and -independent genes (ANAC13) is regulated by different cis-regulatory elements and that (ii) HY5-based chimeric promoters mediate transcription induced by longer wavelength UVB, whereas ANAC13-based promoters respond preferably to broad-band UVB. Importantly, these chimeric promoters do not respond to visible light or other environmental stresses tested, thus they have the potential to be used in applied research to express genes in a UVB-specific fashion. Plants are sessile organisms and have to adapt to the changing environment. Because of the Earth’s rotation, many important environmental factors (light/dark, cold/warm etc.) follow a predictable, periodic pattern. Eukaryotic organisms including plants evolved an endogenous biological clock to optimally time their physiological responses to predictable changes in their environment. To be of use, however, the endogenous time measured by the biological clock must be synchronized to the environmental day/night cycle. Visible light is the most potent signal for this synchronization, but light-induced responses are also rhythmically gated by the clock. Here we provide conclusive evidence for the existence of a similar, mutual interaction between the circadian clock and non-damaging photomorphogenic UVB light. We showed that UVB can entrain the circadian clock and that UVB-induced cellular and molecular events are rhythmically gated by the circadian clock. Accordingly, we demonstrated that UVB acutely induces the transcription of core clock genes including GI, PPR9, ELF4 and CCA1, and that UVR8 and COP1 are required whereas HY5/HYH is dispensable for this process. Our data thus convincingly show that HY5/HYH are associated with different signaling cascades and act differently in visible and UVB light.
Publications
- (2008) Identification of novel cis-regulatory element for UV-B induced transcription in Arabidopsis. Plant J. 54, 402-414
Sáfrány, J., Haasz, V., Máté, Z., Ciolfi, A., Fehér, B., Oravecz, A., Stec A., Dallmann, G., Morelli, G., Ulm, R., Nagy, F.
- (2009) A cell-free system for light-dependent nuclear import of phytochrome. Plant J. 57, 680-689
Pfeiffer, A., Kunkel, T., Hiltbrunner, A., Neuhaus, G., Wolf, I., Speth, V., Adam, E., Nagy, F., Schaefer, E.
- (2009) Interaction of COP1 and UVR8 regulates UVB-induced photomorphogenesis and stress acclimation in Arabidopsis. EMBO J. 28, 591-601
Favory, J-J., Stec, A., Gruber, H., Rizzini, L., Oravecz, A., Funk, M., Albert, A., Cloix, C., Jenkins, G.I., Oakeley, E.J., Seidlitz, H.K., Nagy, F., Ulm, R.
- (2011) Functional interaction of the circadian clock and UV RESISTANCE LOCUS-8 controlled signaling pathways in Arabidopsis thaliana. Plant J. 67:37-48
Feher B, Kozma-Bognar L, Kevei E, Hajdu A, Binkert M, Davis S, Schäfer E, Ulm R, Nagy F
- (2011) Perception of UV-B by the Arabidopsis UVR8 protein. Science 332: 103-106
Rizzini L, Favoury J, Cloix C, Faggionato D, O”Hara A, Kaiserli E, Baumeister R, Schäfer E, Nagy F, Jenkins G, Ulm R
