PIPE Involved In Phytochrome Signaling Pathway In Arabidopsis

As the energy source,light widely influences the growth and development of plants.Plants evolved different photoreceptors to perceive light signal.As a kind of autophosphorylating serine/threonine kinases,phytochrome has been widely studied.In this study,Arabidopsis thaliana mutant pipe was used from an EMS mutagenesis screening in our lab.PIPE gene encoded a type one serine/threonine phosphatase.This mutant showed bigger angle of cotyledons and shorter hypocotyls under red light.So this result suggested that PIPE involved in light signal pathway.Genetic analysis showed that the hypocotyls of phyB pipe double mutants were significantly shorter than phyB,and the hypocotyls of phyA phyB pipe were as long as that of phyA phyB under red light.The hypocotyls length of phyA pipe and phyA were almost the same under far-red light.These results indicated that PIPE and phyB may antagonistically regulate hypocotyl elongation and the genetic interaction of PIPE and phyB is depend on functional phyA.Phytochrome interacting factor,which is a group of basic helix-loop-helix transcription factors were induced by light-activated phys phosphorylation and degradation by the 26S proteasome-mediated pathway,then negatively regulates photomorphogenesis.Statistics founded that the hypocotyl lengths of double mutants pif3 pipe,pif4 pipe,pif5 pipe were as long as mutants pif3,pif4,pif5,respectively.The result indicated that PIPE may participate in degradation of PIFs and act upstream of PIFs.Then,we identified that PIPE directly interacts with phyA,phyB and PIFs in vitro by yeast two-hybrid and pull-down assays;and PIPE can interact with PIF3 and phyB in vivo by BiFC assays.All these results demonstrated that PIPE involved in the phytochrome signaling pathways by interacting with phys and PIFs.