SUMOylation of phytochrome-B negatively regulates light-induced signaling in Arabidopsis thaliana.
The red/far red light absorbing photoreceptor phytochrome-B (phyB) cycles between the biologically inactive (Pr, λmax, 660 nm) and active (Pfr; λmax, 730 nm) forms and functions as a light quality and quantity controlled switch to regulate photomorphogenesis in Arabidopsis. At the molecular level, phyB interacts in a conformation-dependent fashion with a battery of downstream regulatory proteins, including PHYTOCHROME INTERACTING FACTOR transcription factors, and by modulating their activity/abundance, it alters expression patterns of genes underlying photomorphogenesis. Here we report that the small ubiquitin-like modifier (SUMO) is conjugated (SUMOylation) to the C terminus of phyB; the accumulation of SUMOylated phyB is enhanced by red light and displays a diurnal pattern in plants grown under light/dark cycles. Our data demonstrate that (i) transgenic plants expressing the mutant phyB(Lys996Arg)-YFP photoreceptor are hypersensitive to red light, (ii) light-induced SUMOylation of the mutant phyB is drastically decreased compared with phyB-YFP, and (iii) SUMOylation of phyB inhibits binding of PHYTOCHROME INTERACTING FACTOR 5 to phyB Pfr. In addition, we show that OVERLY TOLERANT TO SALT 1 (OTS1) de-SUMOylates phyB in vitro, it interacts with phyB in vivo, and the ots1/ots2 mutant is hyposensitive to red light. Taken together, we conclude that SUMOylation of phyB negatively regulates light signaling and it is mediated, at least partly, by the action of OTS SUMO proteases.
School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, United Kingdom; nagyf@brc.hu ari.sadanandom@durham.ac.uk.
Ari
A
Sadanandom
Plant Biology Institute, Biological Research Centre, H-6726 Szeged, Hungary;
Éva
É
Ádám
School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, United Kingdom;
Beatriz
B
Orosa
Plant Biology Institute, Biological Research Centre, H-6726 Szeged, Hungary;
András
A
Viczián
Institute of Botany, University of Freiburg, D-79104 Freiburg, Germany;
Cornelia
C
Klose
School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, United Kingdom;
Cunjin
C
Zhang
Institute of Molecular Plant Science, School of Biology, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom.
Eve-Marie
EM
Josse
Plant Biology Institute, Biological Research Centre, H-6726 Szeged, Hungary;
László
L
Kozma-Bognár
Plant Biology Institute, Biological Research Centre, H-6726 Szeged, Hungary; Institute of Molecular Plant Science, School of Biology, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom nagyf@brc.hu ari.sadanandom@durham.ac.uk.
Ferenc
F
Nagy
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D008027:Light; D008969:Molecular Sequence Data; D051939:Phytochrome B / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D058207:Sumoylation
D051939:Phytochrome B
photomorphogenesis; photoreceptor; phytochrome; signaling; sumoylation