The histidine kinase-related domain participates in phytochrome B function but is dispensable.
Phytochromes are photoreceptors that control many plant light responses. Phytochromes have two carboxyl-terminal structural domains called the PAS repeat domain and the histidine kinase-related domain. These domains are each related to bacterial histidine kinase domains, and biochemical studies suggest that phytochromes are light-regulated kinases. The PAS repeat domain is important for proper phytochrome function and can interact with putative signaling partners. We have characterized several new phytochrome B mutants in Arabidopsis that express phyB protein, three of which affect the histidine kinase-related domain. Point mutations in the histidine kinase-related domain cause phenotypes similar to those of null mutants, indicating that this domain is important for phyB signaling. However, a truncation that removes most of the histidine kinase-related domain results in a phyB molecule with partial activity, suggesting that this domain is dispensable. These results suggest that phytochromes evolved in modular fashion. We discuss possible functions of the histidine kinase-related domain in phytochrome signaling.
Krall
L
L
University of North Carolina at Chapel Hill, Department of Biology, CB No. 3280, Coker Hall, Chapel Hill, NC 27599-3280, USA.
Reed
J W
JW
D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000528:radiation effects*; D029681:Arabidopsis Proteins; D003116:Color; D004307:Dose-Response Relationship, Radiation; D019143:Evolution, Molecular; D017343:Genes, Plant; D000071677:Histidine Kinase; D018546:Hypocotyl / Q000528:radiation effects; D008027:Light; D009154:Mutation; D017440:Photoperiod; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000235:genetics*; D051939:Phytochrome B; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000235:genetics*; D017434:Protein Structure, Tertiary / Q000235:genetics*; D012098:Reproduction / Q000235:genetics; D017422:Sequence Analysis, DNA; D014157:Transcription Factors
D029681:Arabidopsis Proteins; C497952:PHYB protein, Arabidopsis; D014157:Transcription Factors; D010834:Phytochrome; D051939:Phytochrome B; D011494:Protein Kinases; D000071677:Histidine Kinase