The serine-rich N-terminal domain of oat phytochrome a helps regulate light responses and subnuclear localization of the photoreceptor.
Phytochrome (phy) A mediates two distinct photobiological responses in plants: the very-low-fluence response (VLFR), which can be saturated by short pulses of very-low-fluence light, and the high-irradiance response (HIR), which requires prolonged irradiation with higher fluences of far-red light (FR). To investigate whether the VLFR and HIR involve different domains within the phyA molecule, transgenic tobacco (Nicotiana tabacum cv Xanthi) and Arabidopsis seedlings expressing full-length (FL) and various deletion mutants of oat (Avena sativa) phyA were examined for their light sensitivity. Although most mutants were either partially active or inactive, a strong differential effect was observed for the Delta6-12 phyA mutant missing the serine-rich domain between amino acids 6 and 12. Delta6-12 phyA was as active as FL phyA for the VLFR of hypocotyl growth and cotyledon unfolding in Arabidopsis, and was hyperactive in the VLFR of hypocotyl growth and cotyledon unfolding in tobacco, and the VLFR blocking subsequent greening under white light in Arabidopsis. In contrast, Delta6-12 phyA showed a dominant-negative suppression of HIR in both species. In hypocotyl cells of Arabidopsis irradiated with FR phyA:green fluorescent protein (GFP) and Delta6-12 phyA:GFP fusions localized to the nucleus and coalesced into foci. The proportion of nuclei with abundant foci was enhanced by continuous compared with hourly FR provided at equal total fluence in FL phyA:GFP, and by Delta6-12 phyA mutation under hourly FR. We propose that the N-terminal serine-rich domain of phyA is involved in channeling downstream signaling via the VLFR or HIR pathways in different cellular contexts.
Casal
Jorge J
JJ
IFEVA, Facultad de Agronomía, Universidad de Buenos Aires, Argentina. casal@ifeva.edu.ar
Davis
Seth J
SJ
Kirchenbauer
Daniel
D
Viczian
Andras
A
Yanovsky
Marcelo J
MJ
Clough
Richard C
RC
Kircher
Stefan
S
Jordan-Beebe
Emily T
ET
Schäfer
Eberhard
E
Nagy
Ferenc
F
Vierstra
Richard D
RD
D000872:Anthocyanins / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology; D029681:Arabidopsis Proteins; D018554:Avena / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D002467:Cell Nucleus / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D018546:Hypocotyl / Q000254:growth & development; D008027:Light; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009154:Mutation; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism / Q000528:radiation effects; D010834:Phytochrome / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051942:Phytochrome A; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D012694:Serine / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014026:Nicotiana / Q000235:genetics / Q000502:physiology
D000872:Anthocyanins; D029681:Arabidopsis Proteins; D008164:Luminescent Proteins; C497973:PHYA protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D051942:Phytochrome A; D011993:Recombinant Fusion Proteins; D010834:Phytochrome; D049452:Green Fluorescent Proteins; D012694:Serine