A new type of mutation in phytochrome A causes enhanced light sensitivity and alters the degradation and subcellular partitioning of the photoreceptor.
A specific light program consisting of multiple treatments with alternating red and far-red light pulses was used to isolate mutants in phytochrome A-dependent signal transduction pathways in Arabidopsis. Because of their phenotype, the mutants were called eid for empfindlicher im dunkelroten Licht, which means hypersensitive in far-red light. One of the isolated mutants, eid4, is a novel semi-dominant allele of the phytochrome A gene that carries a missense mutation in the chromophore-binding domain. The mutation did not change the photochemical properties of the photoreceptor, but it leads to an increased stability under light conditions that induce its rapid degradation. Fusion proteins with the green fluorescent protein exhibited clear alterations in subcellular localization of the mutated photoreceptor: The fusion protein was impaired in the formation of sequestered areas of phytochrome in the cytosol, which can explain its reduced light-dependent degradation. In contrast, the mutation stabilizes nuclear speckles (NUS) that appear late under continuous far-red light, whereas the formation of early, transiently appearing NUS remained more or less unaltered.
Dieterle
Monika
M
Institut für Biologie 2/Botanik, Universität Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany.
Bauer
Diana
D
Büche
Claudia
C
Krenz
Martina
M
Schäfer
Eberhard
E
Kretsch
Thomas
T
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins; D001483:Base Sequence; D008027:Light; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010641:Phenotype; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D010834:Phytochrome / Q000235:genetics* / Q000378:metabolism; D051942:Phytochrome A; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; C497973:PHYA protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D051942:Phytochrome A; D011993:Recombinant Fusion Proteins; D010834:Phytochrome; D017346:Protein Serine-Threonine Kinases