Negative feedback regulation of UV-B-induced photomorphogenesis and stress acclimation in Arabidopsis.
Plants respond to low levels of UV-B radiation with a coordinated photomorphogenic response that allows acclimation to this environmental stress factor. The key players in this UV-B response are COP1 (an E3 ubiquitin ligase), UVR8 (a β-propeller protein), and HY5 (a bZIP transcription factor). We have shown previously that an elevated UV-B-specific response is associated with dwarf growth, indicating the importance of balancing UV-B-specific signaling. Negative regulators of this pathway are not known, however. Here, we describe two highly related WD40-repeat proteins, REPRESSOR OF UV-B PHOTOMORPHOGENESIS 1 (RUP1) and RUP2, that interact directly with UVR8 as potent repressors of UV-B signaling. Both genes were transcriptionally activated by UV-B in a COP1-, UVR8-, and HY5-dependent manner. rup1 rup2 double mutants showed an enhanced response to UV-B and elevated UV-B tolerance after acclimation. Overexpression of RUP2 resulted in reduced UV-B-induced photomorphogenesis and impaired acclimation, leading to hypersensitivity to UV-B stress. These results are consistent with an important regulatory role for RUP1 and RUP2, which act downstream of UVR8-COP1 in a negative feedback loop impinging on UVR8 function, balancing UV-B defense measures and plant growth.
Faculty of Biology, Institute of Biology II, University of Freiburg, D-79104 Freiburg, Germany.
Henriette
H
Gruber
Marc
M
Heijde
Werner
W
Heller
Andreas
A
Albert
Harald K
HK
Seidlitz
Roman
R
Ulm
D000064:Acclimatization / Q000528:radiation effects*; D017360:Arabidopsis / Q000254:growth & development* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D025461:Feedback, Physiological / Q000528:radiation effects*; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D009024:Morphogenesis / Q000528:radiation effects*; D009154:Mutation / Q000235:genetics; D011485:Protein Binding / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000528:radiation effects; D013312:Stress, Physiological / Q000528:radiation effects*; D014466:Ultraviolet Rays
D029681:Arabidopsis Proteins; D012333:RNA, Messenger