Phytochromes are red/far-red reversible photoreceptors essential for plant growth and development.Phytochrome signaling is mediated by the physiologically active far-red-absorbing Pfr form that can be inactivated to t...Phytochromes are red/far-red reversible photoreceptors essential for plant growth and development.Phytochrome signaling is mediated by the physiologically active far-red-absorbing Pfr form that can be inactivated to the red-absorbing Pr ground state by light-dependent photoconversion or by light-independent thermal reversion,also termed dark reversion.Although the term“dark reversion”is justified by historical reasons and frequently used in the literature,“thermal reversion”more appropriately describes the process of light-independent but temperature-regulated Pfr relaxation that not only occurs in darkness but also in light and is used throughout the review.Thermal reversion is a critical parameter for the light sensitivity of phytochrome-mediated responses and has been studied for decades,often resulting in contradictory findings.Thermal reversion is an intrinsic property of the phytochrome molecules but can be modulated by intra-and intermolecular interactions,as well as biochemical modifications,such as phosphorylation.In this review,we outline the research history of phytochrome thermal reversion,highlighting important predictions that have been made before knowing the molecular basis.We further summarize and discuss recent findings about the molecular mechanisms regulating phytochrome thermal reversion and its functional roles in light and temperature sensing in plants.展开更多
Photoreceptors of the phytochrome family control a multitude of responses in plants.Phytochrome A(phyA)is essential for far-red light perception,which is important for germination and seedling establishment in strong ...Photoreceptors of the phytochrome family control a multitude of responses in plants.Phytochrome A(phyA)is essential for far-red light perception,which is important for germination and seedling establishment in strong canopy shade.Translocation of phyA from the cytosol into nucleus is a key step in farred light signaling and requires FAR-RED ELONGATED HYPOCOTYL 1(FHY1)and FHY1-LIKE(FHL).FHY1/FHL bind to phyA downstream signaling components.Therefore,it has been suggested that FHY1/FHL also have a function in assembling phyA transcription factor complexes in the nucleus.Yet,in this study,we show that constitutively nuclear-localized phyA is active in the absence of FHY1 and FHL.Furthermore,an artificial FHY1,consisting of an SV40 NLS,a phyA binding site,and a YFP tag as spacer between them,complements the fhy1-3 fhl-1 double mutant.These findings show that FHY1 and FHL are not required for phyA downstream signaling in the nucleus.However,we found that lines expressing phyA-NLS-YFP are hypersensitive to red and far-red light and that slightly increased levels of constitutively nuclear-localized phyA result in photomorphogenic development in the dark.Thus,restricting phyA to the cytosol and inducing nuclear transport in light by interaction with FHY1/FHL might be important to suppress photomorphogenesis in the dark.展开更多
基金supported by the Hungarian Scientific Research Fund(OTKA,K-132633)grants from the Economic Development and Innovation Operative Program(GINO P-2.3.2-15-2016-00001,GI-N OP-2.3.2-15-2016-00015 and GINOP-2.3.2-15-2016-00032).
文摘Phytochromes are red/far-red reversible photoreceptors essential for plant growth and development.Phytochrome signaling is mediated by the physiologically active far-red-absorbing Pfr form that can be inactivated to the red-absorbing Pr ground state by light-dependent photoconversion or by light-independent thermal reversion,also termed dark reversion.Although the term“dark reversion”is justified by historical reasons and frequently used in the literature,“thermal reversion”more appropriately describes the process of light-independent but temperature-regulated Pfr relaxation that not only occurs in darkness but also in light and is used throughout the review.Thermal reversion is a critical parameter for the light sensitivity of phytochrome-mediated responses and has been studied for decades,often resulting in contradictory findings.Thermal reversion is an intrinsic property of the phytochrome molecules but can be modulated by intra-and intermolecular interactions,as well as biochemical modifications,such as phosphorylation.In this review,we outline the research history of phytochrome thermal reversion,highlighting important predictions that have been made before knowing the molecular basis.We further summarize and discuss recent findings about the molecular mechanisms regulating phytochrome thermal reversion and its functional roles in light and temperature sensing in plants.
基金This study was supported by the German Research Foundation(DFG)under Germany’s Excellence Strategy(BIOSS-EXC-294,CIBSS-EXC-2189-Project ID 390939984)by grants from the DFG(DFG HI 1369/4-1 and HI 1369/5-1)+2 种基金the Human Frontier Science Program Organization(HFSP research grant RGP0025/2013)to A.H.C.K.was supported by the Ministry of Science,Research and the Arts Baden-WuerttembergThe article processing charge was funded by the German Research Foundation(DFG)and the Albert Ludwigs University Freiburg in the funding programme Open Access Publishing.
文摘Photoreceptors of the phytochrome family control a multitude of responses in plants.Phytochrome A(phyA)is essential for far-red light perception,which is important for germination and seedling establishment in strong canopy shade.Translocation of phyA from the cytosol into nucleus is a key step in farred light signaling and requires FAR-RED ELONGATED HYPOCOTYL 1(FHY1)and FHY1-LIKE(FHL).FHY1/FHL bind to phyA downstream signaling components.Therefore,it has been suggested that FHY1/FHL also have a function in assembling phyA transcription factor complexes in the nucleus.Yet,in this study,we show that constitutively nuclear-localized phyA is active in the absence of FHY1 and FHL.Furthermore,an artificial FHY1,consisting of an SV40 NLS,a phyA binding site,and a YFP tag as spacer between them,complements the fhy1-3 fhl-1 double mutant.These findings show that FHY1 and FHL are not required for phyA downstream signaling in the nucleus.However,we found that lines expressing phyA-NLS-YFP are hypersensitive to red and far-red light and that slightly increased levels of constitutively nuclear-localized phyA result in photomorphogenic development in the dark.Thus,restricting phyA to the cytosol and inducing nuclear transport in light by interaction with FHY1/FHL might be important to suppress photomorphogenesis in the dark.
