Blue Light Receptors and Signal Transduction
Year: 2002
Type: article
Abstract: Functions of Blue Light Receptors in Phototropism, Photomorphogenesis, and Photoperiodic Flowering. Solid arrows depict light, and dashed arrows depict signal transduction of photoreceptors. Cryptochromes share sequence similarity to the DNA repair enzyme photolyase but have no DNA repair activity. Cryptochromes and DNA photolyases share similarities not only in amino acid sequences but also in chromophore composition and in the light-dependent nature of their respective biochemical activities. Cryptochromes appear to be evolutionarily derived from gene duplication events of ancestral photolyase genes, because many organisms, including Arabidopsis and Drosophila, are known to have both cryptochromes and photolyases, functioning as photoreceptors and DNA repair enzymes, respectively (Cashmore et al., 1999). Cryptochromes, which were historically defined by their action spectra, are photolyase-like blue light receptors (Gressel, 1979; Briggs and Huala, 1999; Cashmore et al., 1999; Lin, 2000b). Most organisms examined to date have more than one cryptochrome, and different cryptochromes of the same organism often mediate related light responses. No biochemical activity has been demonstrated for a cryptochrome, but the expression of a cryptochrome gene may be regulated by light via different mechanisms from transcription to degradation. DNA photolyases are ∼55 to 65 kD flavoproteins widely found in microbes including bacteria, Archaea, and yeast (Sancar, 1994). Photolyases catalyze blue/UV-A light–dependent repair of DNA damage resulting from exposure to high-energy short-wavelength (<350 nm) UV light (UV-B and UV-C). There are two types of structurally related DNA photolyases, one (called photolyase) that repairs cyclobutane pyrimidine dimers and another (called 6-4 photolyase) that repairs pyrimidine-pyrimidine 6-4 photoproducts (Sancar, 1994, 2000). A phylogenetic analysis indicated that plant cryptochromes are more closely related to the photolyases than to the 6-4 photolyases, whereas animal cryptochromes are more closely related to 6-4 photolyases than to the photolyase (Cashmore et al., 1999). Therefore, it appears that plant cryptochromes and animal cryptochromes arose from independent gene duplications of their respective ancestral photolyase genes. Most plant cryptochromes are 70- to 80-kD proteins with two recognizable domains, an amino terminal PHR (for photolyase-related) domain that shares sequence homology with photolyases and a carboxyl terminal domain that has no strong sequence similarity to known protein domains (Cashmore et al., 1999; Mockler and Lin, unpublished data). Photolyase contains two chromophores, a light-harvesting chromophore, which is either a folate (methenyltetrahydrofolate) or a deazaflavin, and a catalytic chromophore that is flavin adenine dinucleotide (FAD). Almost all residues known to be important for chromophore binding in photolyase are conserved in cryptochromes, whereas residues of photolyases that are critical for the binding of DNA lesions and the catalysis of DNA repair are not equally conserved in cryptochromes (Ahmad and Cashmore, 1993; Todo et al., 1996; Imaizumi et al., 2000). The chromophore composition of cryptochromes has been investigated using recombinant cryptochrome purified from heterologous expression systems. The full-length Arabidopsis CRY1 expressed and purified from insect cells non-covalently binds a stoichiometric amount of FAD (Lin et al., 1995b). The PHR domain of Arabidopsis CRY1 expressed as a fusion protein to maltose binding protein (CRY1N-MBP) and purified from Escherichia coli also contained non-covalently bound FAD, indicating that the PHR domain is indeed the chromophore binding domain of cryptochrome. the recombinant protein purified from coli contains the light-harvesting chromophore found in many photolyases (Sancar, et al., with the that cryptochromes are no photolyase activity in different in and expression of cryptochromes not the coli (Lin et al., et al., et al., 1996; Imaizumi et al., et al., 2000). Cryptochromes have been found in and Cashmore, 1993; 1993; et al., et al., and Cashmore, 1996; Imaizumi et al., et al., and Imaizumi et al., Imaizumi et al., and et al., Most plant Arabidopsis has two cryptochrome genes, CRY1 and (Ahmad and Cashmore, 1993; et al., 1996; et al., and and have cryptochrome genes, and et al., and have and two cryptochrome genes, respectively and Imaizumi et al., The amino acid sequences of CRY1 or and are more to their Arabidopsis than to that the gene duplication resulting in CRY1 and the of and et al., et al., 2000). Most plant cryptochromes a in to the PHR and the domain has been found to be critical to the of Arabidopsis and (Ahmad et al., et al., and Lin, unpublished data). the domains of different cryptochromes in from amino in amino and amino in Arabidopsis CRY1 and to no in the of and of the The PHR gene to a DNA photolyase but it found to have no DNA repair activity and is to be a cryptochrome et al., have not been for or is to that contains no amino acid sequence is to the PHR domain of the Arabidopsis which is than that the two Arabidopsis A of activity of of or of more the of the of the cryptochrome. of Blue Light domains of PHR and domains of cryptochrome, and folate are The of domains is not to the in the Arabidopsis that are to the exposure to light et al., 1999; et al., 1999; et al., Arabidopsis cryptochromes to in the either or in the Arabidopsis to be a protein by both analysis and fusion protein et al., 1999; et al., 1999; et al., 2000). proteins of and were found to in the of the in or in light, that Arabidopsis is a A that Arabidopsis may be with et al., 2000). Arabidopsis were examined for the of fusion a that expressed the fusion protein found to to all et al., another fusion protein found to in the of in the et al., 2000). Blue light the of of the fusion which with the by fusion protein were et al., 2000). cells with a gene Arabidopsis CRY1 and fusion protein were to protein in the (Cashmore et al., 1999). a fusion protein of and the CRY1 domain found in the in Arabidopsis but in the in et al., 2000). Therefore, Arabidopsis appears to be in the or in or light, The of all cryptochromes in the has been that and are whereas and are proteins et al., 2000). is to the in in but not in blue light, whereas in the et al., 2000). the PHR domain of a cryptochrome may be to the sequence for because photolyases are proteins in the of many cryptochromes are found in their the of fusion proteins of and their to be regulated by light, the action of the cryptochromes or in the that the domains of Arabidopsis CRY1 and both and Arabidopsis CRY1 and appears to be expressed the plant with no found in different or in with different light (Ahmad and Cashmore, 1993; et al., CRY1 and have been by a DNA analysis to with a of et al., 2000). CRY1 and and gene no light for their expression et al., et al., 2000). the gene expression is light and both and light of expression have been for cryptochrome 1993; Imaizumi et al., 2000). The of the gene in to to or blue light et al., 2000). of a in Arabidopsis in or light and depict The of in two are not in the of cryptochromes in plant with the of the of Arabidopsis cryptochromes in gene and are by both cryptochromes and in to blue/UV-A and of light, A plant in an with a that the no to from to light in or The of of of gene and of the is to and it has the widely in the of Arabidopsis CRY1 the of the of the in blue light of et al., and Cashmore, in blue light, a blue light of resulting from of the CRY1 or Arabidopsis Arabidopsis CRY1 than of the in blue light (Lin et al., indicating that the amount of is in the of blue light of The that of Arabidopsis CRY1 in also in a that the is conserved in different plant of with have been in a of using Arabidopsis or in both types of photoreceptors and and Cashmore, et al., and and and et al., and et al., Arabidopsis also a in blue light, which to the that is also in were by for in blue light et al., in blue light, (Lin et al., The of is more in light than in light, which is as the of protein in blue light (Lin et al., There is an and because the has more in of than either the or et al., 1999; et al., A of and in is also by the that in light in et al., 2000). to cryptochromes have also been to mediate blue light of of The Arabidopsis is in light-dependent indicating in blue light (Ahmad et al., et al., The in blue light, a of in (Lin et al., The activity of and in for in light has also been et al., et al., with the that cryptochrome signal transduction is conserved in different a of cryptochromes in has also been in a contained protein and in blue light but not in light et al., 1999). a has been et al., of the that blue light of in et al., to the Arabidopsis the is also in and in blue light, indicating the of Arabidopsis and cryptochromes in et al., of the gene in the and have been et al., of the demonstrated that and in a to mediate blue light of of blue light of and blue light of et al., is by a of signal transduction that to of the important is or the it is known that are photoreceptors a for cryptochrome in has been The of cryptochrome in the of has been investigated by of Arabidopsis with either light or light of The of Arabidopsis in has been demonstrated by than the in light and et al., The of Arabidopsis in has also been using the the Arabidopsis the of in et al., it that the is and to and it is to a et al., et al., The than the in but not in whereas in but not in Therefore, either a or an of the gene in the to blue light is known to of the found to the same as the in blue light or light et al., The of in light be in light et al., Mockler et al., 1999). Therefore, the of is both blue light and A of the and a of the of the blue light is both blue light and light with to the of that a light–dependent of whereas a blue light–dependent of the et al., Mockler et al., 1999). to the action of also the of in the of found that the the same as the were in light et al., 2000). of is that the in light may activity in which the of the of the gene et al., 2000). with the that may mediate light–dependent of it found that the to in the with light and Lin, unpublished data). The cryptochromes and that the of in light is in by the action of different photoreceptors or the The of in is demonstrated by a of a that the of in Arabidopsis et al., the of the in the and The which is for the and of the to be the protein with a for the conserved different cryptochrome for the gene of with the to whereas the with a the that the in the protein is indeed the of the of the it found that the of the protein in a in the of The protein with the a of of protein expression in that the expression of protein in to in the and in of gene expression is a which photoreceptors in plant as of There are two mechanisms by which light may transcription of a light may transcription via signal transduction from a to et al., et al., or light may gene expression the action of the and and Cashmore, The is of and a that is a transcription for which activity and are regulated by light in a 1999; and 2000). Cryptochromes have been demonstrated to be photoreceptors light of the in Drosophila, and cryptochrome as an of the in a has to be demonstrated for plant as a functioning in the of the has been in A the of in the of activity of the et al., et al., The of and expression et al., to blue light of the et al., and the of the et al., cryptochrome et al., 2000b). cryptochrome is not the only that the in The an of the in blue light the signal transduction for the is also et al., Therefore, as in is a cryptochromes and in plant and in The of cryptochrome is not in but in it has been that cryptochrome the by with The of and 1999). and are and for the transcription of genes. and are proteins that to transcription of as and The transcription of the and is by their gene and in the and the to their found that cryptochrome with in a light-dependent and the in of and of of transcription et al., 1999). cryptochromes have also been to as photoreceptors for the of the and gene the of cryptochromes as photoreceptors the been an of and et al., et al., 1999; et al., 1999; et al., 1999; et al., 1999; et al., 2000). and have two cryptochromes et al., 1996; Todo et al., The both and in but an and of in that are of the et al., 1999). The that cryptochromes are of the it to their in the light of the it found that to the to mediate light the signal transduction of also et al., 2000). both cryptochrome and a were and a in gene expression et al., 1999). of cryptochromes with proteins have also been has been that cryptochromes with of or proteins to transcription of in et al., 1999; et al., 1999; et al., et al., organisms a may be that it an organism to and be for an in the a plant to proteins for and proteins in with an of the is not that light is the important for the and activity of the because in to for light also many as and The of cryptochromes in of the plant indicated by the that the Arabidopsis in the of chromophore in the blue light of of activity et al., and that the Arabidopsis the of the expression of a gene et al., The of cryptochromes in the of the using Arabidopsis in either the CRY1 or the gene et al., of the of the activity were light in the that the than of the in both and of blue light, indicating the of in the of the a of light the the a in only in of blue light, that not the blue light the the of in the of the demonstrated the found to have than either the or in both and of blue light and 2000). and in the of the cryptochromes may in of the because the a of the in of light and 2000). to the found in et al., Arabidopsis and indicating that cryptochromes may not as of the in to their as photoreceptors the cryptochromes also mediate light of gene expression in is known to be the blue light light of expression of as in Arabidopsis et al., and in blue light of which a more in the than in the or et al., of gene expression the transcription expression in to blue/UV-A light in the than in the et al., to the blue light of expression that is regulated by appears to be the blue light the activity of the et al., the expression of the in to light in the than that in the et al., to their in genes, Arabidopsis and have been found to be in light of transcription et al., of or transcription activity than that of the The blue activity by in the et al., is not many may be regulated by it has been that and are both for blue transcription of et al., of gene expression has been in Arabidopsis using DNA expressed sequence et al., genes, a of of the are either or in to blue the blue light gene expression investigated using the and the it found that blue light of of the were by or of is that the two of expression in to blue light are regulated by cryptochromes and because have been to both blue light to the and blue light of activity of and et al., et al., et al., The of cryptochrome signal transduction is from that cryptochromes with that of a may a of of cryptochrome with The cryptochrome to of or in gene or resulting in of in to of The of cryptochrome has been to be a (Cashmore et al., 1999; 2000). is the known of The of two photolyases coli and have been et al., et al., The of a photolyase is two domains, a domain and a The light-harvesting chromophore or is bound to a the two domains, and FAD is bound in the of the the DNA repair a photolyase binds to the DNA light by the light-harvesting chromophore folate is to the catalytic chromophore FAD, a is from FAD to the cyclobutane of pyrimidine to two and a from pyrimidine to FAD the of the (Sancar, 1994). is that the of two photolyases, which share only sequence and different light-harvesting are et al., et al., is that the PHR domain of a cryptochrome, in the of Arabidopsis shares to sequence with coli photolyase (Ahmad and Cashmore, may have a to that of a one may that the light of a cryptochrome that of a an flavin of a cryptochrome and a in an flavin and the protein of the cryptochrome, resulting in in the either an to the or a the may to biochemical as of the cryptochrome, and of the cryptochrome and proteins it binds signal Arabidopsis cryptochromes have been found to blue light–dependent and Lin, unpublished data). Blue light signal transduction has been to of cryptochromes with that Arabidopsis CRY1 with in yeast and that recombinant CRY1 in an in (Ahmad et al., Arabidopsis CRY1 found to be in light in and the in the of light (Ahmad et al., to may also with with a that Arabidopsis and with a domain in yeast and in and et al., et al., has been found to an important in the of the and in because in or of the gene a of the of and and et al., et al., The of and protein that the from photoreceptors to the may be appears to be an of the Arabidopsis has been demonstrated to with et al., 2000). The by both yeast and using an to and fusion indicating that two photoreceptors in in a light-dependent et al., 2000). that is for the of from a that but not with in the et al., 2000). The that mediate light of transcription via with the transcription et al., et al., and the and et al., that of of transcription may be an important of cryptochrome signal cryptochromes and also a for the of two types of photoreceptors that has been in 2000). the for blue light signal the blue activity of cryptochromes in the of cryptochromes and protein is because it may another for cryptochrome signal transduction and et al., et al., may be that cryptochrome is the of domain a in the it demonstrated that of fusion proteins of and cryptochrome domains a et al., 2000). or fusion proteins and were in or in light, of the of et al., 2000). are of found for the are and often whereas the expression a but not et al., et al., et al., 2000). in the CRY1 including and which been to activity (Ahmad et al., the of fusion proteins to the of a fusion which is by residues the of than not a et al., 1999). be to the of expression of with or because the two different fusion proteins different to the residues in are with a that cryptochromes with or proteins in a light-dependent to the activity of proteins in to light et al., 2000). the found in cryptochrome and et al., et al., et al., that full-length or or fusion proteins with in yeast et al., et al., of the from the that cells and in the which were expressed but not expressed et al., The not to be may also with found that with in both yeast and et al., not using a yeast in another et al., or fusion proteins more of the transcription in the which is to that in the et al., 2000). gene expression of and are which also to that of blue or the et al., is a and protein that has a to both are in the in but in the in light and et al., 2000). has been to as a of an with of the transcription in the et al., 2000). are with a transcription for the et al., et al., to with in the to the of gene expression and light, is with from the an of the transcription and transcription of for of appears to many of the with to blue light responses. to transcription as of are also in signal signal of Blue is one of the blue light and from the of in to blue light and Arabidopsis and are in both the blue and blue of indicating that the of a critical in the of cryptochromes and 1996; and of has also been to be with blue light and 1996; and Arabidopsis to blue/UV-A found that blue light in the and that that or blue/UV-A expression and 1996; and the and to be a of the Arabidopsis gene has a of a in cryptochrome et al., The is to blue and light with to and gene expression indicated that from cryptochromes in a but it is a than a protein for protein contains two binding and an in binding indicated that is a binding protein et al., protein is with the et al., and Lin, unpublished data). is that blue light may a of the the which in activity and of photoreceptors or are plant and in to light to in whereas from blue light to that in for and light for but from light to by two cells in their in to light, in the to but to blue light is the of light in and Huala, 1999). The blue light receptors plant have the of in it has that the of blue light receptors all and as a kD protein that blue light–dependent in and including Arabidopsis et al., and and it found that the light-dependent of protein a in a Arabidopsis indicating in et al., The gene protein from another Arabidopsis (for that is in both and in to light and et al., in the gene were found in different in with the of and cryptochromes, the and the and are to as and respectively et al., Arabidopsis a that contains two domains the and a domain the carboxyl the two domains of are more closely related to found in a of proteins that are regulated by light, and were to as domains et al., expressed in insect cells binds flavin and it a blue light–dependent in The and of the recombinant are to the action of in with the demonstrated that is a blue The domain expressed and purified from coli cells indicating that domains are the chromophore binding of and that a contains two et al., 1999). have also been found in plant including and et al., Briggs et al., Briggs and is that a gene a in the of an domain to chromophore binding domains and a domain that a full-length et al., The that is a protein is by the that both a chromophore and the blue/UV-A chromophore et al., et al., 1999). in as for which is a blue light the in and be by both blue light and light, which is with the that that is a in to in the also the in a of Arabidopsis in the of in to light, it found that one of the to and both were to both and blue light with to it also found in that the in to blue light of than in the The that the in of blue light indicated the of another et al., 2000). cryptochromes were in the the for in Arabidopsis to be another which as (Ahmad et al., et al., 1999; et al., The Arabidopsis gene the of sequence similarity to et al., The amino acid sequence of is to that of A and examined for blue light et al., a light which light resulting from found to be in in light but not in light, the of in but not in a to mediate the et al., a it in Arabidopsis that blue light of but from blue light that to the and 2000). 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The because of in but it also a in The gene an a domain the terminal and a domain the but it is not known may with and be by also contains a signal and many domain proteins are known to with transcription it is that or domain proteins may the signal from the to transcription in the transcription from has been to be an The as a in blue and it that the not only but also and gene expression et al., the of be by a of the gene in et al., 2000). The gene an et al., to the transcription that is in and is regulated by et al., is with to the of because is known for in et al., that as a transcription in to light and et al., 2000). may also the of A blue of in the recombinant protein et al., 1999). in is to because it in the but not in the or et al., 1999). is that may catalyze of the in the and the of is to that the which is in but not in and in blue and blue of both were in the and and that blue light of may cryptochrome to and and may be with of and of is the for which the of the photoreceptors has to more the with than that with either or and et al., is that of blue may to for the from with and responses. may the in in which the of the the of the and the of is also that may with and the to the of resulting in of blue light that of many of signal transduction in has been by Arabidopsis mechanisms of signal signal and to be the biochemical nature of the of cryptochromes is not or types of protein have been found for cryptochrome is to be the is
Source: The Plant Cell
DOI: 10.1105/tpc.000646
Author: Chentao Lin
Institution: University of California, Los Angeles
Language: English
Topic: Light effects on plants
Subfield: Plant Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2163630793