Article Abstract:
An analysis of the effects of microinjecting putative signaling intermediates into phytochrome-deficient tomato cells by developing single-cell assays demonstrated that phytochrome phototransduction needs to be activated by G proteins. These G proteins are added to two different pathways. The first needs calcium and activated calmodulin which can stimulate the characteristics of a photo regulated Cab-GUS reporter gene in conjunction with the synthesis and grouping of some of the photosynthetic complexes. The other pathway, involving anthocyanin biosynthesis, does not require calcium. Phytochrome signaling does not require any light-activated steps of the G protein.
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Article Abstract:
A phytochrome-interactor factor (PIF3), a basic helix-loop-helix protein with a PAS domain, was identified utilizing a yeast two-hybrid screen. PIF3 binds to wild-type C-terminal domains of both phyA and phyB, but less strongly to signaling-defective, missense mutant-containing domains. Expression of sense or antisense PIF3 sequences in transgenic Arabidopsis upsets photoresponsiveness in a manner indicating that PIF3 acts in both phyA and phyB signaling pathways in vivo.
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Article Abstract:
Phytochromes and protein kinases have an association that may serve a functional importance. Phytochromes evolved from an ancestral histidine kinase of prokaryotes but they also exhibit serine kinase activities. Phytochromes, therefore, are atypical members of the histidine kinase superfamily. The functional homology between phytochromes and histidine kinases is still unsettled.
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