Photoreceptor-Mediated Bending towards UV-B in Arabidopsis
Vandenbussche, Filip × Tilbrook, Kimberley Fierro, Ana Carolina Marchal, Kathleen Poelman, Dirk Van Der Straeten, Dominique Ulm, Roman #
Oxford University Press
Molecular Plant vol:7 issue:6 pages:1041-52
Plants reorient their growth towards light to optimize photosynthetic light capture, a process known as phototropism. Phototropins are the photoreceptors essential for phototropic growth towards blue and ultraviolet-A (UV-A) light. Here we detail a phototropic response towards UV-B in etiolated Arabidopsis seedlings. We report that early differential growth is mediated by phototropins but clear phototropic bending to UV-B is maintained in phot1 phot2 double mutants. We further show that this phototropin-independent phototropic response to UV-B requires the UV-B photoreceptor UVR8. Broad UV-B-mediated repression of auxin-responsive genes suggests that UVR8 regulates directional bending by affecting auxin signalling. Kinetic analysis shows that UVR8-dependent directional bending occurs later than the phototropin response. We conclude that plants may use the full short wavelength spectrum of sunlight to efficiently reorient photosynthetic tissue with incoming light.