Blue Light Sensing in Higher Plants

Plants have evolved a range of sophisticated mechanisms to adapt and respond to their natural habitat. For example, plants rely heavily upon the surrounding light environment to direct their growth and development. Several different photoreceptor families are known to mediate the effects of light on plant development (1Ahmad M. Curr. Opin. Plant Biol. 1999; 2: 230-235Crossref PubMed Scopus (40) Google Scholar, 2Batschauer A. Cell. Mol. Life Sci. 1999; 55: 153-166Crossref PubMed Scopus (44) Google Scholar, 3Maheshwari S.C. Khurana J.P. Sopory S.K. J. Biosci. 2000; 24: 499-514Crossref Scopus (7) Google Scholar). These include the phytochrome (phy) family of photoreceptors, which monitor the red (600–700 nm) and far-red (700–750 nm) regions of the solar spectrum (4Neff M.M. Fankhauser C. Chory J. Genes Dev. 2000; 14: 257-271Crossref PubMed Google Scholar). In addition to the phytochromes, many important aspects of plant development are regulated by specific blue (390–500 nm) and/or UV-A (320–390 nm) light-absorbing receptors (5Briggs W.R. Huala E. Annu. Rev. Cell Dev. 1999; 15: 33-62Crossref PubMed Scopus (330) Google Scholar, 6Cashmore A.R. Jarillo J.A. Wu Y-J. Liu D. Science. 1999; 284: 760-765Crossref PubMed Scopus (783) Google Scholar, 7Lin C. Trends Plant Sci. 2000; 5: 337-342Abstract Full Text Full Text PDF PubMed Scopus (191) Google Scholar). Currently two classes of blue light receptors have been identified in plants: the cryptochromes and the phototropins. Here we briefly review the most recent advances in our understanding of blue light perception and signaling with an emphasis on the cryptochrome and phototropin photosensory systems.Cloning of the HY4 Gene Encoding Cryptochrome 1Our present knowledge of blue light perception would not be possible without the isolation of photoregulatory mutants. The rationale behind the genetic approach has been to screen for mutants with altered responses to light. For example, when dark-grownArabidopsis seedlings are transferred to light, hypocotyl elongation is dramatically suppressed (Fig.1A). This response is mediated by blue, red, and far-red light in Arabidopsis (8Khurana J.P. Kochhar A. Tyagi A.K. Crit. Rev. Plant Sci. 1998; 17: 465-539Crossref Google Scholar). Screening for an elongated hypocotyl phenotype in white light has resulted in the isolation of both phytochrome and blue light regulatory mutants. One of these long hypocotyl mutants, cry1(originally designated hy4), is specifically impaired in its ability to respond to blue light (Fig. 1A).The HY4 gene was isolated through the use of ahy4 mutant allele tagged with a T-DNA insertion (9Ahmad M. Cashmore A.R. Nature. 1993; 366: 162-166Crossref PubMed Scopus (1009) Google Scholar). Examination of the deduced amino acid sequence revealed that theHY4 gene encodes a 75-kDa protein with significant sequence homology to microbial DNA photolyases (Fig.2). Sequence homology is highest in the regions associated with chromophore binding. The HY4 gene was therefore proposed to encode a photoreceptor that mediates the blue light inhibition of hypocotyl elongation (9Ahmad M. Cashmore A.R. Nature. 1993; 366: 162-166Crossref PubMed Scopus (1009) Google Scholar). Based on further characterization, the hy4 protein was named cryptochrome 1 (cry1), a term previously introduced to describe the enigmatic nature of plant blue/UV-A photoreceptors and their presumed prevalance in lower plants and fungi (cryptogams) (10Gressel J. Photochem. Photobiol. 1977; 30: 749-754Crossref Scopus (63) Google Scholar).Figure 2Protein of E. amino amino Arabidopsis amino Arabidopsis amino amino of and are in a for photolyases are to be the for the cryptochromes 6Cashmore A.R. Jarillo J.A. Wu Y-J. Liu D. Science. 1999; 284: 760-765Crossref PubMed Scopus (783) Google Scholar). are blue in both and that the of DNA to nm) A. PubMed Scopus Google Scholar). and photolyases mediate the of photolyases the of In the two blue/UV-A light-absorbing (Fig. The is the of the and to the of the to the The a a is the of the protein and an light to the the C. M. Cashmore A.R. Science. PubMed Scopus Google Scholar, A. A. PubMed Scopus Google Scholar). The protein a that is in the photolyases (Fig. the chromophore to a that light C. M. Cashmore A.R. Science. PubMed Scopus Google Scholar). The of is with the that light to C. M. D. Cashmore A.R. Sci. A. PubMed Scopus Google Scholar). In has been to a when A. A. PubMed Scopus Google the are impaired in a of growth J.A. PubMed Scopus Google Scholar). The photoreceptor to the blue light of by the of and J.A. Plant Sci. Scopus Google photoreceptors have been identified in plant M. Mol. 1998; PubMed Scopus Google and Plant Mol. Biol. PubMed Scopus Google and to be the plant of cryptochrome homology to (Fig. Arabidopsis a designated and and A. A. PubMed Scopus Google Scholar, A. Mol. PubMed Scopus Google Scholar). In addition to has been to blue inhibition of hypocotyl elongation and M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar, J. Cashmore A.R. Sci. A. 1998; PubMed Scopus Google Scholar). in to is in response to blue light M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar, J. Cashmore A.R. Sci. A. 1998; PubMed Scopus Google Scholar, C. Plant J. 1999; PubMed Scopus Google Scholar). The in protein to the that light light to the blue light inhibition of hypocotyl elongation M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar, J. Cashmore A.R. Sci. A. 1998; PubMed Scopus Google and many plant the of the to development is regulated by In long plants the to is by long the a phenotype white light and are to the mutant that is in the C. Science. 1998; PubMed Scopus Google with far-red blue light with red light has an C. Plant 2000; PubMed Scopus Google Scholar). light through the of red light mediates its through the of C. Plant 2000; PubMed Scopus Google Scholar). blue light the response to be in the mutant the plants blue red light C. Science. 1998; PubMed Scopus Google Scholar). the phenotype of white light be by with both blue and red light C. Science. 1998; PubMed Scopus Google Scholar, C. 1999; PubMed Google Scholar). a has been proposed to by in response to blue light C. 1999; PubMed Google mutant a blue light, phenotype is with mutants these C. 1999; PubMed Google Scholar). in addition to to in response to blue light. In the of the is mediated by photoreceptors has been to for a of plant responses and is known to of the and different photoreceptor families Photochem. Photobiol. 2000; PubMed Scopus Google and the are mechanisms that to a of and with the The of a that the an that the in response to light, and an that the to responses Plant 1999; PubMed Scopus Google Scholar). has been to mediate of the Arabidopsis plants the gene to the protein a of Science. PubMed Scopus Google Scholar). This a to the of plant photoreceptors in the In the of a in the mutant when plants are transferred to blue light Science. 1998; PubMed Scopus Google Scholar). of the of on the has on the that a in This is the of in the of C. Science. 1998; PubMed Scopus Google Scholar, C. 1999; PubMed Google Scholar). the of on not the of the the by on signaling C. Trends Plant Sci. 2000; 5: 337-342Abstract Full Text Full Text PDF PubMed Scopus (191) Google Scholar, C. Plant 2000; PubMed Scopus Google Scholar). and in a to the with the mutant have been identified in A.R. Jarillo J.A. Wu Y-J. Liu D. Science. 1999; 284: 760-765Crossref PubMed Scopus (783) Google Scholar). the plant cryptochromes and A. A. PubMed Scopus Google Scholar). and cryptochromes have been to a in light of the M. M. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, M. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, M. M. J. A. D. D. A. Nature. 1999; Google Scholar). sequence that cryptochromes the photolyases A. A. PubMed Scopus Google Scholar, M. M. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, M. Science. PubMed Scopus Google plant cryptochromes are to the photolyases (9Ahmad M. Cashmore A.R. Nature. 1993; 366: 162-166Crossref PubMed Scopus (1009) Google Scholar). is therefore proposed that plant and cryptochromes have the of (1Ahmad M. Curr. Opin. Plant Biol. 1999; 2: 230-235Crossref PubMed Scopus (40) Google Scholar, 6Cashmore A.R. Jarillo J.A. Wu Y-J. Liu D. Science. 1999; 284: 760-765Crossref PubMed Scopus (783) Google their homology to the cryptochromes to by to a specific protein for has been and Arabidopsis have been to in the (1Ahmad M. Curr. Opin. Plant Biol. 1999; 2: 230-235Crossref PubMed Scopus (40) Google Scholar, C. Plant J. 1999; PubMed Scopus Google Scholar, A. Plant J. 1999; PubMed Scopus Google Scholar). of light was on C. Plant J. 1999; PubMed Scopus Google these the that cryptochromes blue gene by with DNA a of was in the of plants C. Plant J. 1999; PubMed Scopus Google Scholar). and to blue associated with the of the of and in signaling is This is in photolyases and to be for cryptochrome M. C. Cashmore A.R. Plant J. PubMed Scopus Google Scholar). the of and in and these regions are that both photoreceptors the signaling M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar). The of with and the of a in A. Photochem. Photobiol. PubMed Scopus Google Scholar). a for plant cryptochromes to be the of the in cryptochrome signaling has recent to the of both and mediates a phenotype in Arabidopsis seedlings Wu Y-J. Liu D. Liu Cashmore A.R. Cell. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). of the and a of and the of that the regions of and are to that the cryptochromes through a of the have that Arabidopsis and with in and for M. Jarillo J.A. Cashmore A.R. Mol. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). has been to with in a Nature. 2000; PubMed Scopus Google Scholar). these that photosensory different photoreceptor light a of the in hypocotyl of plant Arabidopsis Plant Cell 2000; PubMed Scopus Google Scholar). The the blue light inhibition of hypocotyl elongation and is proposed to a signaling associated with The blue in of a Sci. A. PubMed Scopus Google Scholar). a of with that is in by Plant Cell 2000; PubMed Scopus Google Scholar, Plant 1998; PubMed Scopus Google Scholar). the the of blue light on both and hypocotyl elongation Sci. A. PubMed Scopus Google Scholar). the blue light inhibition of hypocotyl growth be two a inhibition a and a inhibition that blue light Plant 1998; PubMed Scopus Google Scholar). by to be in the inhibition of hypocotyl growth Plant Cell 2000; PubMed Scopus Google Scholar). growth inhibition in response to blue light is in mutant and to be Plant 1998; PubMed Scopus Google that response is mediated by a photosensory the known and be to both and growth inhibition in and to a of responses in mutants a of blue light example, the of blue/UV-A photoreceptors of the Gene Encoding on have to the of a family of blue light is the plants a light to light for and UV-A light are the most for in Screening for an altered response to blue light has resulted in the isolation of a of mutants S.C. Khurana J.P. Sopory S.K. J. Biosci. 2000; 24: 499-514Crossref Scopus (7) Google Scholar, W.R. Huala E. Annu. Rev. Cell Dev. 1999; 15: 33-62Crossref PubMed Scopus (330) Google Scholar, E. Photochem. Photobiol. 2000; PubMed Scopus Google Scholar). One of these mutants, hypocotyl 1 to of blue light (Fig. the blue of a protein E. W.R. Plant Cell. PubMed Scopus Google Scholar). has that the is in the response (5Briggs W.R. Huala E. Annu. Rev. Cell Dev. 1999; 15: 33-62Crossref PubMed Scopus (330) Google Scholar, W.R. Annu. Rev. Plant Plant Mol. Biol. Scopus Google Scholar). The was therefore proposed to a that in response to blue light E. W.R. Plant Cell. PubMed Scopus Google gene was isolated by a and to encode a protein of amino E. E. E. W.R. Science. PubMed Scopus Google Scholar). is to be associated with the upon isolation and plant W.R. Plant PubMed Scopus Google that is a protein with E. E. E. W.R. Science. PubMed Scopus Google Scholar). a protein to with the The of the in protein S.K. J. PubMed Scopus Google (Fig. The of the protein a of amino that to the are in a of and are to mediate and to of and light Mol. Biol. Rev. 1999; Google Scholar). The of are to a of the that are regulated by the of designated and E. E. E. W.R. Science. PubMed Scopus Google nature of a is by the of a specific Mol. Biol. Rev. 1999; Google Scholar). The of are and a blue light-absorbing in and in response to blue light E. W.R. Science. 1998; PubMed Scopus Google Scholar). the spectrum of E. W.R. Science. 1998; PubMed Scopus Google and the of the isolated M. M. W.R. Sci. A. 1999; PubMed Scopus Google are to the spectrum for with and and a The protein was therefore named phototropin its in M. M. W.R. Sci. A. 1999; PubMed Scopus Google Scholar).Figure by the of phototropin light. the proposed of a the chromophore and a the a of photoreceptors, to the cryptochromes of phototropin homology to phototropin J.A. M. Cashmore A.R. Plant 1998; (Fig. of phototropin have been identified in plant M. M. M. M. Plant Cell 2000; PubMed Scopus Google W.R. M. Plant 2000; PubMed Google and In a isolated the of both phytochrome and phototropin photoreceptors M. M. W.R. Sci. A. 1999; PubMed Scopus Google Scholar, M. Sci. A. 1998; PubMed Scopus Google Scholar). is therefore possible that the effects of red and blue light on of are mediated by a the of Arabidopsis E. J. M. and when in that a photoreceptor M. M. and the phototropin M. A. A. and recent has that a photoreceptor is to mediate in Arabidopsis Plant Cell. 2000; PubMed Scopus Google Scholar). mutants of phototropin in response to of blue light hypocotyl is mutants the Plant Cell. 2000; PubMed Scopus Google be important to the response of a mutant to an photoreceptor for that the cryptochromes a in M. Jarillo J.A. Cashmore A.R. Nature. 1998; PubMed Scopus Google mutants to blue light J. E. A. W.R. Plant 1999; PubMed Scopus Google (Fig. is possible that the the phytochromes, to the response light W.R. D. Plant by be and E. in for M. M. W.R. Sci. A. 1999; PubMed Scopus Google and an to the of have that both and of phototropin light and a M. E. W.R. 2000; PubMed Scopus Google Scholar). The of the for and of a of a with an a the of both and M. E. W.R. 2000; PubMed Scopus Google Scholar). light by phototropin to the of a the chromophore and the the (Fig. the is with the of an the of the of the which is the Sci. A. PubMed Scopus Google Scholar). is therefore that the of the in a of the phototropin which in to of the M. E. W.R. 2000; PubMed Scopus Google Scholar). the isolated a in light M. E. W.R. 2000; PubMed Scopus Google that and have with the protein to the of and in blue light their the to through a to for phototropin has been that is the is that phototropin signaling through to a associated with a phototropin signaling through a in response to of phototropin a in are many to be was identified by the isolation of mutants E. W.R. Plant Cell. PubMed Scopus Google Scholar, A. E. Science. 1999; PubMed Scopus Google Scholar). is a protein and with phototropin in A. E. Science. 1999; PubMed Scopus Google Scholar). is associated with the and is proposed to an to of the signaling protein to designated was isolated a genetic screen Plant Cell. 2000; PubMed Scopus Google Scholar). In to gene is light a in have that is in phototropin light a in in which is impaired in that phototropin to the of a Sci. A. 1999; PubMed Scopus Google Scholar). for protein in has been in plant E. Photochem. Photobiol. 2000; PubMed Scopus Google Scholar). is therefore possible that the of associated with the of a protein by a in E. Photochem. Photobiol. 2000; PubMed Scopus Google has two classes of blue/UV-A photoreceptors in plants: the cryptochromes and the phototropins. is that For example, the spectrum for the of a Plant 2000; PubMed Scopus Google Scholar). recent genetic and that a chromophore be in response E. J. J. 1998; Google Scholar, E. Plant Cell 2000; PubMed Scopus Google Scholar). The isolation of blue/UV-A response mutants the of blue/UV-A light receptors in of and mutants to the of these photoreceptors in blue Plants have evolved a range of sophisticated mechanisms to adapt and respond to their natural habitat. For example, plants rely heavily upon the surrounding light environment to direct their growth and development. Several different photoreceptor families are known to mediate the effects of light on plant development (1Ahmad M. Curr. Opin. Plant Biol. 1999; 2: 230-235Crossref PubMed Scopus (40) Google Scholar, 2Batschauer A. Cell. Mol. Life Sci. 1999; 55: 153-166Crossref PubMed Scopus (44) Google Scholar, 3Maheshwari S.C. Khurana J.P. Sopory S.K. J. Biosci. 2000; 24: 499-514Crossref Scopus (7) Google Scholar). These include the phytochrome (phy) family of photoreceptors, which monitor the red (600–700 nm) and far-red (700–750 nm) regions of the solar spectrum (4Neff M.M. Fankhauser C. Chory J. Genes Dev. 2000; 14: 257-271Crossref PubMed Google Scholar). In addition to the phytochromes, many important aspects of plant development are regulated by specific blue (390–500 nm) and/or UV-A (320–390 nm) light-absorbing receptors (5Briggs W.R. Huala E. Annu. Rev. Cell Dev. 1999; 15: 33-62Crossref PubMed Scopus (330) Google Scholar, 6Cashmore A.R. Jarillo J.A. Wu Y-J. Liu D. Science. 1999; 284: 760-765Crossref PubMed Scopus (783) Google Scholar, 7Lin C. Trends Plant Sci. 2000; 5: 337-342Abstract Full Text Full Text PDF PubMed Scopus (191) Google Scholar). Currently two classes of blue light receptors have been identified in plants: the cryptochromes and the phototropins. Here we briefly review the most recent advances in our understanding of blue light perception and signaling with an emphasis on the cryptochrome and phototropin photosensory of the HY4 Gene Encoding Cryptochrome 1Our present knowledge of blue light perception would not be possible without the isolation of photoregulatory mutants. The rationale behind the genetic approach has been to screen for mutants with altered responses to light. For example, when dark-grownArabidopsis seedlings are transferred to light, hypocotyl elongation is dramatically suppressed (Fig.1A). This response is mediated by blue, red, and far-red light in Arabidopsis (8Khurana J.P. Kochhar A. Tyagi A.K. Crit. Rev. Plant Sci. 1998; 17: 465-539Crossref Google Scholar). Screening for an elongated hypocotyl phenotype in white light has resulted in the isolation of both phytochrome and blue light regulatory mutants. One of these long hypocotyl mutants, cry1(originally designated hy4), is specifically impaired in its ability to respond to blue light (Fig. 1A).The HY4 gene was isolated through the use of ahy4 mutant allele tagged with a T-DNA insertion (9Ahmad M. Cashmore A.R. Nature. 1993; 366: 162-166Crossref PubMed Scopus (1009) Google Scholar). Examination of the deduced amino acid sequence revealed that theHY4 gene encodes a 75-kDa protein with significant sequence homology to microbial DNA photolyases (Fig.2). Sequence homology is highest in the regions associated with chromophore binding. The HY4 gene was therefore proposed to encode a photoreceptor that mediates the blue light inhibition of hypocotyl elongation (9Ahmad M. Cashmore A.R. Nature. 1993; 366: 162-166Crossref PubMed Scopus (1009) Google Scholar). Based on further characterization, the hy4 protein was named cryptochrome 1 (cry1), a term previously introduced to describe the enigmatic nature of plant blue/UV-A photoreceptors and their presumed prevalance in lower plants and fungi (cryptogams) (10Gressel J. Photochem. Photobiol. 1977; 30: 749-754Crossref Scopus (63) Google Scholar). present knowledge of blue light perception would not be possible without the isolation of photoregulatory mutants. The rationale behind the genetic approach has been to screen for mutants with altered responses to light. For example, when dark-grownArabidopsis seedlings are transferred to light, hypocotyl elongation is dramatically suppressed (Fig.1A). This response is mediated by blue, red, and far-red light in Arabidopsis (8Khurana J.P. Kochhar A. Tyagi A.K. Crit. Rev. Plant Sci. 1998; 17: 465-539Crossref Google Scholar). Screening for an elongated hypocotyl phenotype in white light has resulted in the isolation of both phytochrome and blue light regulatory mutants. One of these long hypocotyl mutants, cry1(originally designated hy4), is specifically impaired in its ability to respond to blue light (Fig. The HY4 gene was isolated through the use of ahy4 mutant allele tagged with a T-DNA insertion (9Ahmad M. Cashmore A.R. Nature. 1993; 366: 162-166Crossref PubMed Scopus (1009) Google Scholar). Examination of the deduced amino acid sequence revealed that theHY4 gene encodes a 75-kDa protein with significant sequence homology to microbial DNA photolyases (Fig.2). Sequence homology is highest in the regions associated with chromophore binding. The HY4 gene was therefore proposed to encode a photoreceptor that mediates the blue light inhibition of hypocotyl elongation (9Ahmad M. Cashmore A.R. Nature. 1993; 366: 162-166Crossref PubMed Scopus (1009) Google Scholar). Based on further characterization, the hy4 protein was named cryptochrome 1 (cry1), a term previously introduced to describe the enigmatic nature of plant blue/UV-A photoreceptors and their presumed prevalance in lower plants and fungi (cryptogams) (10Gressel J. Photochem. Photobiol. 1977; 30: 749-754Crossref Scopus (63) Google Scholar). a for photolyases are to be the for the cryptochromes 6Cashmore A.R. Jarillo J.A. Wu Y-J. Liu D. Science. 1999; 284: 760-765Crossref PubMed Scopus (783) Google Scholar). are blue in both and that the of DNA to nm) A. PubMed Scopus Google Scholar). and photolyases mediate the of photolyases the of In the two blue/UV-A light-absorbing (Fig. The is the of the and to the of the to the The a a is the of the protein and an light to the DNA photolyases are to be the for the cryptochromes 6Cashmore A.R. Jarillo J.A. Wu Y-J. Liu D. Science. 1999; 284: 760-765Crossref PubMed Scopus (783) Google Scholar). are blue in both and that the of DNA to nm) A. PubMed Scopus Google Scholar). and photolyases mediate the of photolyases the of In the two blue/UV-A light-absorbing (Fig. The is the of the and to the of the to the The a a is the of the protein and an light to the Cryptochrome the C. M. Cashmore A.R. Science. PubMed Scopus Google Scholar, A. A. PubMed Scopus Google Scholar). The protein a that is in the photolyases (Fig. the chromophore to a that light C. M. Cashmore A.R. Science. PubMed Scopus Google Scholar). The of is with the that light to C. M. D. Cashmore A.R. Sci. A. PubMed Scopus Google Scholar). In has been to a when A. A. PubMed Scopus Google the are impaired in a of growth J.A. PubMed Scopus Google Scholar). The photoreceptor to the blue light of by the of and J.A. Plant Sci. Scopus Google photoreceptors have been identified in plant M. Mol. 1998; PubMed Scopus Google and Plant Mol. Biol. PubMed Scopus Google and to be the plant of cryptochrome homology to (Fig. Arabidopsis a designated and and A. A. PubMed Scopus Google Scholar, A. Mol. PubMed Scopus Google Scholar). In addition to has been to blue inhibition of hypocotyl elongation and M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar, J. Cashmore A.R. Sci. A. 1998; PubMed Scopus Google Scholar). in to is in response to blue light M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar, J. Cashmore A.R. Sci. A. 1998; PubMed Scopus Google Scholar, C. Plant J. 1999; PubMed Scopus Google Scholar). The in protein to the that light light to the blue light inhibition of hypocotyl elongation M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar, J. Cashmore A.R. Sci. A. 1998; PubMed Scopus Google Scholar). the C. M. Cashmore A.R. Science. PubMed Scopus Google Scholar, A. A. PubMed Scopus Google Scholar). The protein a that is in the photolyases (Fig. the chromophore to a that light C. M. Cashmore A.R. Science. PubMed Scopus Google Scholar). The of is with the that light to C. M. D. Cashmore A.R. Sci. A. PubMed Scopus Google Scholar). In has been to a when A. A. PubMed Scopus Google Scholar). the are impaired in a of growth J.A. PubMed Scopus Google Scholar). The photoreceptor to the blue light of by the of and J.A. Plant Sci. Scopus Google Scholar). Cryptochrome photoreceptors have been identified in plant M. Mol. 1998; PubMed Scopus Google and Plant Mol. Biol. PubMed Scopus Google and to be the plant of cryptochrome homology to (Fig. Arabidopsis a designated and and A. A. PubMed Scopus Google Scholar, A. Mol. PubMed Scopus Google Scholar). In addition to has been to blue inhibition of hypocotyl elongation and M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar, J. Cashmore A.R. Sci. A. 1998; PubMed Scopus Google Scholar). in to is in response to blue light M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar, J. Cashmore A.R. Sci. A. 1998; PubMed Scopus Google Scholar, C. Plant J. 1999; PubMed Scopus Google Scholar). The in protein to the that light light to the blue light inhibition of hypocotyl elongation M. Jarillo J.A. Cashmore A.R. Plant Cell. 1998; PubMed Scopus Google Scholar, J. Cashmore A.R. Sci. A. 1998; PubMed Scopus Google Scholar). and many plant the of the to development is regulated by In long plants the to is by long the a phenotype white light and are to the mutant that is in the C. Science. 1998; PubMed Scopus Google with far-red blue light with red light has an C. Plant 2000; PubMed Scopus Google Scholar). light through the of red light mediates its through the of C. Plant 2000; PubMed Scopus Google Scholar). blue light the response to be in the mutant the plants blue red light C. Science. 1998; PubMed Scopus Google Scholar). the phenotype of white light be by with both blue and red light C. Science. 1998; PubMed Scopus Google Scholar, C. 1999; PubMed Google Scholar). a has been proposed to by in response to blue light C. 1999; PubMed Google mutant a blue light, phenotype is with mutants these C. 1999; PubMed Google Scholar). in addition to to in response to blue light. In the of the is mediated by photoreceptors has been to for a of plant responses and is known to of the and different photoreceptor families Photochem. Photobiol. 2000; PubMed Scopus Google Scholar). For many plant the of the to development is regulated by In long plants the to is by long the a phenotype white light and are to the mutant that is in the C. Science. 1998; PubMed Scopus Google Scholar). In with far-red blue light with red light has an C. Plant 2000; PubMed Scopus Google Scholar). light through the of red light mediates its through the of C. Plant 2000; PubMed Scopus Google Scholar). blue light the response to be in the mutant the plants blue red light C. Science. 1998; PubMed Scopus Google Scholar). the phenotype of white light be by with both blue and red light C. Science. 1998; PubMed Scopus Google Scholar, C. 1999; PubMed Google Scholar). a has been proposed to by in response to blue light C. 1999; PubMed Google Scholar). The mutant a blue light, phenotype is with mutants these C. 1999; PubMed Google Scholar). in addition to to in response to blue light. In the of the is mediated by photoreceptors has been to for a of plant responses and is known to of the and different photoreceptor families Photochem. Photobiol. 2000; PubMed Scopus Google Scholar). and the are mechanisms that to a of and with the The of a that the an that the in response to light, and an that the to responses Plant 1999; PubMed Scopus Google Scholar). has been to mediate of the Arabidopsis plants the gene to the protein a of Science. PubMed Scopus Google Scholar). This a to the of plant photoreceptors in the In the of a in the mutant when plants are transferred to blue light Science. 1998; PubMed Scopus Google Scholar). of the of on the has on the that a in This is the of in the of C. Science. 1998; PubMed Scopus Google Scholar, C. 1999; PubMed Google Scholar). the of on not the of the the by on signaling C. Trends Plant Sci. 2000; 5: 337-342Abstract Full Text Full Text PDF PubMed Scopus (191) Google Scholar, C. Plant 2000; PubMed Scopus Google Scholar). and in a to the with the mutant have been identified in A.R. Jarillo J.A. Wu Y-J. Liu D. Science. 1999; 284: 760-765Crossref PubMed Scopus (783) Google Scholar). the plant cryptochromes and A. A. PubMed Scopus Google Scholar). and cryptochromes have been to a in light of the M. M. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, M. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, M. M. J. A. D. D. A. Nature. 1999; Google Scholar). sequence that cryptochromes the photolyases A. A. PubMed Scopus Google Scholar, M. M. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, M. Science. PubMed Scopus Google plant cryptochromes are to the photolyases (9Ahmad M. Cashmore A.R. Nature. 1993; 366: 162-166Crossref PubMed Scopus (1009) Google Scholar). is therefore proposed