Different phototransduction kinetics of phytochrome A and phytochrome B in Arabidopsis thaliana.
The kinetics of phototransduction of phytochrome A (phyA) and phytochrome B (phyB) were compared in etiolated Arabidopsis thaliana seedlings. The responses of hypocotyl growth, cotyledon unfolding, and expression of a light-harvesting chlorophyll a/b-binding protein of the photosystem II gene promoter fused to the coding region of beta-glucuronidase (used as a reporter enzyme) were mediated by phyA under continuous far-red light (FR) and by phyB under continuous red light (R). The seedlings were exposed hourly either to n min of FR followed by 60 minus n min in darkness or to n min of R, 3 min of FR (to back-convert phyB to its inactive form), and 57 minus n min of darkness. For the three processes investigated here, the kinetics of phototransduction of phyB were faster than that of phyA. For instance, 15 min R h-1 (terminated with a FR pulse) were almost as effective as continuous R, whereas 15 min of FR h-1 caused less than 30% of the effect of continuous FR. This difference is interpreted in terms of divergence of signal transduction pathways downstream from phyA and phyB.
Casal
J J
JJ
Departmento de Ecología, Universidad de Buenos Aires, Argentina.
Cerdán
P D
PD
Staneloni
R J
RJ
Cattaneo
L
L
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D029681:Arabidopsis Proteins; D005966:Glucuronidase / Q000235:genetics; D008027:Light; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000378:metabolism*; D051942:Phytochrome A; D051939:Phytochrome B; D011401:Promoter Regions, Genetic; D015398:Signal Transduction / Q000528:radiation effects*; D014157:Transcription Factors
D029681:Arabidopsis Proteins; C497973:PHYA protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; D051942:Phytochrome A; D014157:Transcription Factors; D010834:Phytochrome; D051939:Phytochrome B; D005966:Glucuronidase