Arabidopsis HEMERA/pTAC12 initiates photomorphogenesis by phytochromes.
Light plays a profound role in plant development, yet how photoreceptor excitation directs phenotypic plasticity remains elusive. One of the earliest effects of light is the regulated translocation of the red/far-red photoreceptors, phytochromes, from the cytoplasm to subnuclear foci called phytochrome nuclear bodies. The function of these nuclear bodies is unknown. We report the identification of hemera, a seedling lethal mutant of Arabidopsis with altered phytochrome nuclear body patterns. hemera mutants are impaired in all phytochrome responses examined, including proteolysis of phytochrome A and phytochrome-interacting transcription factors. HEMERA was identified previously as pTAC12, a component of a plastid complex associated with transcription. Here, we show that HEMERA has a function in the nucleus, where it acts specifically in phytochrome signaling, is predicted to be structurally similar to the multiubiquitin-binding protein, RAD23, and can partially rescue yeast rad23mutants. Together, these results implicate phytochrome nuclear bodies as sites of proteolysis.
Chen
Meng
M
Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA. chen.meng@duke.edu <chen.meng@duke.edu>
Galvão
Rafaelo M
RM
Li
Meina
M
Burger
Brian
B
Bugea
Jane
J
Bolado
Jack
J
Chory
Joanne
J
D017360:Arabidopsis / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000032:analysis; D047908:Intracellular Signaling Peptides and Proteins; D008027:Light; D018613:Microscopy, Confocal; D009687:Nuclear Proteins / Q000378:metabolism; D051942:Phytochrome A / Q000378:metabolism*; D051939:Phytochrome B / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*
D029681:Arabidopsis Proteins; C088435:DET1 protein, Arabidopsis; D004268:DNA-Binding Proteins; C000604706:HMR protein, Arabidopsis; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; C497952:PHYB protein, Arabidopsis; D051942:Phytochrome A; C490846:RAD23 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D051939:Phytochrome B; D049452:Green Fluorescent Proteins