Bioelectromagnetics 36:476^479 (2015)
Brief Communication Suppression of Arabidopsis Flowering by Near-Null Magnetic Field is Affected by Light Chunxiao Xu,* Yue Li,YangYu,Yuxia Zhang, and ShufengWei Beijing Key Laboratory of Bioelectromagnetism, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China We previously reported that a near-null magnetic field suppressed Arabidopsis flowering in white light, which might be related to the function modification of cryptochrome (CRY). To further demonstrate that the effect of near-null magnetic field on Arabidopsis flowering is associated with CRY, Arabidopsis wild type and CRY mutant plants were grown in the near-null magnetic field under blue or red light with different light cycle and photosynthetic photon flux density. We found that Arabidopsis flowering was significantly suppressed by near-null magnetic field in blue light with lower intensity (10 mmol/m2/s) and shorter cycle (12 h period: 6 h light/6 h dark). However, flowering time of CRY1/CRY2 mutants did not show any difference between plants grown in nearnull magnetic field and in local geomagnetic field under detected light conditions. In red light, no significant difference was shown in Arabidopsis flowering between plants in near-null magnetic field and local geomagnetic field under detected light cycles and intensities. These results suggest that changes of blue light cycle and intensity alter the effect of near-null magnetic field on Arabidopsis flowering, which is mediated by CRY. Bioelectromagnetics. 36:476–479, 2015. © 2015 Wiley Periodicals, Inc. Key words: blue light; cryptochrome; light cycle; light intensity; red light
Photoperiodic flowering of plants is regulated by photosensory receptors including the red/far-red light receptor phytochrome and blue/UV-A light receptor cryptochrome (CRY). Arabidopsis phyA mediates far red light promotion of flowering, while phyB mediates red light inhibition of flowering. CRY1 and CRY2 mediate blue light promotion of flowering [Lin, 2000; Mockler et al., 2003]. Arabidopsis is a facultative longday plant that flowers earlier in a long-day photoperiod than in a short-day one [Levy and Dean, 1998]. Arabidopsis flowering in blue light was more sensitive to the photoperiod than that of plants in red light, suggesting that CRY played a major role on flowering regulation [Mockler et al., 2003]. Blue light-dependent phosphorylation of CRY is closely associated with its function. Phosphorylation of Arabidopsis CRY1 and CRY2 increased with enhancement of photosynthetic photon flux density (PPFD) and elongation of blue light exposure time [Shalitin et al., 2002,2003]. These results indicated that light intensity and exposure time affected the function of CRYs, which implied that flowering of Arabidopsis mediated by CRY could also be affected by changes of light intensity and exposure time. In magnetoreception research, CRY, first found in Arabidopsis, was suggested to be a magnetoreceptor 2015 Wiley Periodicals, Inc.
based on radical-pair mechanism [Ritz et al., 2000]. Then, photo-induced flavin-tryptophan radical pairs in Arabidopsis CRY1 were confirmed to be magnetically sensitive, implying that the function of CRY could be modified by magnetic field [Maeda et al., 2012]. The CRY mutants of Drosophila melanogaster lost the ability to respond to a magnetic field, while wild-type flies showed significant naive and trained responses to the magnetic field [Gegear et al., 2008]. Human and butterfly (Danaus plexippus) CRY genes could rescue the response of Drosophila cry mutants to magnetic Grant sponsors: National Natural Science Foundation of China; grant numbers: 31470824, 31000382; Institute of Electrical Engineering of Chinese Academy of Sciences; grant number: 0950111CS1. Conflict of interest: None. *Correspondence to: Chunxiao Xu, Institute of Electrical Engineering, Chinese Academy of Sciences, Zhongguancun, Beijing, 100190, P. R. China. E-mail: [email protected] Received for review 14 January 2015; Accepted 21 May 2015 DOI: 10.1002/bem.21927 Published online 11 June 2015 in Wiley Online Library (wileyonlinelibrary.com).
Arabidopsis in Near-Null Magnetic Field
field, suggesting that the function of CRY was conserved in different species [Gegear et al., 2010; Foley et al., 2011]. We previously reported that Arabidopsis flowering in a near-null magnetic field was delayed compared to that of plants in the local geomagnetic field in white light under 16 h light and 8 h dark condition, suggesting that near-null magnetic field suppressed Arabidopsis flowering [Xu et al., 2012]. In addition, we found that blue light-dependent phosphorylation of CRY weakened and dephosphorylation of CRY enhanced in Arabidopsis in near-null magnetic field, implying this magnetic field affected the function of CRY [Xu et al., 2014]. Previous research confirmed that CRY activation was blue light-dependent, and magnetic field effect on photo-induced flavin-tryptophan radical pairs in Arabidopsis CRY1 also required blue light, suggesting that magnetic field effect on the function of CRY was mediated by blue light [Yu et al., 2007; Maeda et al., 2012]. Therefore, it is possible that light change alters the effect of near-null magnetic field on Arabidopsis flowering. To test whether light alters the effect of near-null magnetic field on Arabidopsis flowering, we grew Arabidopsis seedlings in near-null magnetic field and local geomagnetic field under blue or red light with different light cycle and PPFD. Arabidopsis flowering was analyzed. Arabidopsis thaliana Columbia ecotype Col-4 (Lehle seeds, Round Rock, TX) was used for experiments. The CRY1/CRY2 mutant [Mockler et al., 1999] used in this study was of Col stock. Surface sterilized seeds were sown on a 1:2 mixture of peat moss and vermiculite in quadrate plastic plates (20 cm inside) and maintained at 4 8C in darkness for 2 days for seed germination consistency. Low-temperaturetreated seeds were then illuminated with white light (30 mmol/m2/s) for 12 h to promote germination, and grown in near-null magnetic field and local geomagnetic field illuminated with blue or red light at 21 0.5 8C. Magnetic field generating equipment and magnetic field treatments of Arabidopsis plants were as described previously [Xu et al., 2013]. Overhead light was provided by light emitting diodes (LEDs) placed 40 cm above the central location of the magnetic field generating equipment. These provided homogeneous light intensity for growth of Arabidopsis seedlings by using diffusers between lights and plants. To test light cycle effect on Arabidopsis flowering, Arabidopsis seedlings were grown in 10 mmol/m2/s blue (460 nm) or red light (650 nm) under continuous light, 12 h L/ 12 h D (24 h period) and 6 h L/6 h D (12 h period) conditions. We grew Arabidopsis seedlings in 10, 20,
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and 30 mmol/m2/s blue or red lights under a 6 h L/6 h D (12 h period) condition to research the effect of light intensity on Arabidopsis flowering. Flowering times of Arabidopsis were measured as described in Mockler et al. [1999]. When grown in 10 mmol/m2/s blue light, flowering of Arabidopsis plants in near-null magnetic field was different under different light cycles. In continuous light and 12 h L/12 h D conditions, flowering time of Arabidopsis wild-type plants in near-null magnetic field did not show significant difference from that of plants in local geomagnetic field (Fig. 1a). However, in the 6 h L/6 h D condition, flowering time of Arabidopsis wild-type plants in near-null magnetic field was delayed significantly compared to that of controls (Fig. 1a). These results indicated that the effect of near-null magnetic field on Arabidopsis flowering was affected by light cycle change, and the significant effect of near-null magnetic field on Arabidopsis flowering was shown in the shorter light
Fig. 1. a: Flowering time of Arabidopsis plants in near-null magnetic field (N) and local geomagnetic field (G) under three different blue light cycles. Data are means SE of four independent experiments. PPFD of light was 10 mmol/m 2 /s. Significance levels for t-test: P < 0.01. CL: continuous light. b: Flowering time of Arabidopsis plants in near-null magnetic field (N) and local geomagnetic field (G) under 10, 20, or 30 mmol/m2 /s blue light with 6 h L/6 h D cycle. Data are means SE of four independent experiments. Significance levels for t-test: P < 0.01. Bioelectromagnetics
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cycle. The flowering time of CRY1/CRY2 mutants in near-null magnetic field did not show significant difference from local geomagnetic field control in three detected light cycles (Fig. 1a). These results suggested that CRY was involved in suppression of Arabidopsis flowering by near-null magnetic field. Furthermore, we grew Arabidopsis plants in 20 and 30 mmol/m2/s lights under 6 h L/6 h D condition, and found that flowering time of Arabidopsis wild-type plants in near-null magnetic field did not show a significant difference from that of controls, indicating that change of light intensity altered the effect of nearnull magnetic field on Arabidopsis flowering (Fig. 1b). Also, flowering time of CRY1/CRY2 mutants in near-null magnetic field did not show any difference from local geomagnetic field control under detected light intensities (Fig. 1b). In red light, flowering time of Arabidopsis wildtype plants in near-null magnetic field did not show significant difference from that of plants in local geomagnetic field under three detected light cycles and intensities, indicating that near-null magnetic field did not affect Arabidopsis flowering in red light (Fig. 2). Also, the flowering time of CRY1/CRY2 mutants in the near-null magnetic field did not show any difference from the local geomagnetic field control in three detected light cycles and intensities (Fig. 2). These results suggested that the near-null magnetic field did not affect red light receptor involved Arabidopsis flowering. In our present study, we found that suppression of Arabidopsis flowering by near-null magnetic field was shown in the shorter blue light cycle. It was reported that CRY activation depended on blue light, and the activated CRY would be converted to the inactivated state in dark condition [Yu et al., 2007]. Shortening the blue light cycle provided more chances to convert CRY between active and inactive states. Moreover, photo-induced flavin-tryptophan radical pairs in Arabidopsis CRY1 could be affected by magnetic field [Maeda et al., 2012]. Phosphorylation and dephosphorylation of CRY in Arabidopsis were affected by near-null magnetic field [Xu et al., 2014]. Shortening of blue light cycle provided better chances for near-null magnetic field to affect the function of CRY, and, therefore, Arabidopsis flowering. We also found near-null magnetic field effect on Arabidopsis flowering was not significantly shown in blue light with higher intensity. Increase of PPFD of blue light could enhance the function of CRY [Shalitin et al., 2002, 2003]. Thus, we speculate that increase of blue light intensity overcomes the effect of near-null magnetic field on CRY-involved flowering. However, data on the relation between blue light intensity and Bioelectromagnetics
Fig. 2. a: Flowering time of Arabidopsis plants in near-null magnetic field (N) and local geomagnetic field (G) under three different red light cycles. Data are means SE of four independent experiments. PPFD of light was 10 mmol/m2 /s. CL: continuous light. b: Flowering time of Arabidopsis plants in the near-null magnetic field (N) and local geomagnetic field (G) under 10, 20, or 30 mmol/m 2 /s red light with 6 h L/6 h D cycle. Data are means SE of four independent experiments.
Arabidopsis flowering are deficient so far [Yu et al., 2010]. Further research is necessary to demonstrate the effect of blue light intensity on Arabidopsis flowering, and the extent of the effect of near-null magnetic field on the function of CRY. ACKNOWLEDGMENTS We thank Lin Chentao (Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles) for supplying of Arabidopsis seeds. REFERENCES Foley LE, Gegear RJ, Reppert SM. 2011. Human CRY exhibits light-dependent magnetosensitivity. Nat Commun http://dx.doi.org/10.1038/ncomms1364. [Last accessed 10 Jan 2015].
Arabidopsis in Near-Null Magnetic Field Gegear RJ, Casselman A, Waddell S, Reppert SM. 2008. CRY mediates light-dependent magnetosensitivity in Drosophila. Nature 454:1014–1018. Gegear RJ, Foley LE, Casselman A, Reppert SM. 2010. Animal CRYs mediate magnetoreception by an unconventional photochemical mechanism. Nature 463:804–807. Levy YY, Dean C. 1998. The transition to flowering. Plant Cell 10:1973–1990. Lin C. 2000. Photoreceptors and regulation of flowering time. Plant Physiol 123:39–50. Maeda K, Robinson AJ, Henbest KB, Hogben HJ, Biskup T, Ahmad M, Schleicher E, Weber S, Timmel CR, Hore PJ. 2012. Magnetically sensitive light-induced reactions in CRY are consistent with its proposed role as a magnetoreceptor. Proc Natl Acad Sci USA 109:4774–4779. Mockler TC, Guo H, Yang H, Duong H, Lin C. 1999. Antagonistic actions of Arabidopsis CRYs and phytochrome B in the regulation of floral induction. Development 126:2073– 2082. Mockler T, Yang H, Yu X, Parikh D, Cheng Y, Dolan S, Lin C. 2003. Regulation of photoperiodic flowering by Arabidopsis photoreceptors. Proc Natl Acad Sci USA 100:2140–2145. Ritz T, Adem S, Schulten K. 2000. A model for photoreceptorbased magnetoreception in birds. Biophys J 78:707–718.
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Shalitin D, Yang H, Mockler TC, Maymon M, Guo H, Whitelam GC, Lin C. 2002. Regulation of Arabidopsis CRY 2 by blue-light-dependent phosphorylation. Nature 417: 763–767. Shalitin D, Yu X, Maymon M, Mockler T, Lin C. 2003. Blue light-dependent in vivo and in vitro phosphorylation of Arabidopsis CRY 1. Plant Cell 15:2421–2429. Xu C, Yin X, Lv Y, Wu C, Zhang Y, Song T. 2012. A near-null magnetic field affects CRY-related hypocotyl growth and flowering in Arabidopsis. Adv Space Res 49:834–840. Xu C, Wei S, Lu Y, Zhang Y, Chen C, Song T. 2013. Removal of the local geomagnetic field affects reproductive growth in Arabidopsis. Bioelectromagnetics 34:437–442. Xu C, Lv Y, Chen C, Zhang Y, Wei S. 2014. Blue light-dependent phosphorylations of CRYs are affected by magnetic fields in Arabidopsis. Adv Space Res 53:1118–1124. Yu X, Shalitin D, Liu X, Maymon M, Klejnot J, Yang H, Lopez J, Zhao X, Bendehakkalu KT, Lin C. 2007. Derepression of the NC80 motif is critical for the photoactivation of Arabidopsis C RY2. Proc Natl Acad Sci USA 104:7289– 7294. Yu X, Liu H, Klejnot J, Lin C. 2010. The CRY blue light receptors. The Arabidopsis Book 8:e0135. DOI: 10.1199/ tab.0135
Bioelectromagnetics
Brief Communication Suppression of Arabidopsis Flowering by Near-Null Magnetic Field is Affected by Light Chunxiao Xu,* Yue Li,YangYu,Yuxia Zhang, and ShufengWei Beijing Key Laboratory of Bioelectromagnetism, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China We previously reported that a near-null magnetic field suppressed Arabidopsis flowering in white light, which might be related to the function modification of cryptochrome (CRY). To further demonstrate that the effect of near-null magnetic field on Arabidopsis flowering is associated with CRY, Arabidopsis wild type and CRY mutant plants were grown in the near-null magnetic field under blue or red light with different light cycle and photosynthetic photon flux density. We found that Arabidopsis flowering was significantly suppressed by near-null magnetic field in blue light with lower intensity (10 mmol/m2/s) and shorter cycle (12 h period: 6 h light/6 h dark). However, flowering time of CRY1/CRY2 mutants did not show any difference between plants grown in nearnull magnetic field and in local geomagnetic field under detected light conditions. In red light, no significant difference was shown in Arabidopsis flowering between plants in near-null magnetic field and local geomagnetic field under detected light cycles and intensities. These results suggest that changes of blue light cycle and intensity alter the effect of near-null magnetic field on Arabidopsis flowering, which is mediated by CRY. Bioelectromagnetics. 36:476–479, 2015. © 2015 Wiley Periodicals, Inc. Key words: blue light; cryptochrome; light cycle; light intensity; red light
Photoperiodic flowering of plants is regulated by photosensory receptors including the red/far-red light receptor phytochrome and blue/UV-A light receptor cryptochrome (CRY). Arabidopsis phyA mediates far red light promotion of flowering, while phyB mediates red light inhibition of flowering. CRY1 and CRY2 mediate blue light promotion of flowering [Lin, 2000; Mockler et al., 2003]. Arabidopsis is a facultative longday plant that flowers earlier in a long-day photoperiod than in a short-day one [Levy and Dean, 1998]. Arabidopsis flowering in blue light was more sensitive to the photoperiod than that of plants in red light, suggesting that CRY played a major role on flowering regulation [Mockler et al., 2003]. Blue light-dependent phosphorylation of CRY is closely associated with its function. Phosphorylation of Arabidopsis CRY1 and CRY2 increased with enhancement of photosynthetic photon flux density (PPFD) and elongation of blue light exposure time [Shalitin et al., 2002,2003]. These results indicated that light intensity and exposure time affected the function of CRYs, which implied that flowering of Arabidopsis mediated by CRY could also be affected by changes of light intensity and exposure time. In magnetoreception research, CRY, first found in Arabidopsis, was suggested to be a magnetoreceptor 2015 Wiley Periodicals, Inc.
based on radical-pair mechanism [Ritz et al., 2000]. Then, photo-induced flavin-tryptophan radical pairs in Arabidopsis CRY1 were confirmed to be magnetically sensitive, implying that the function of CRY could be modified by magnetic field [Maeda et al., 2012]. The CRY mutants of Drosophila melanogaster lost the ability to respond to a magnetic field, while wild-type flies showed significant naive and trained responses to the magnetic field [Gegear et al., 2008]. Human and butterfly (Danaus plexippus) CRY genes could rescue the response of Drosophila cry mutants to magnetic Grant sponsors: National Natural Science Foundation of China; grant numbers: 31470824, 31000382; Institute of Electrical Engineering of Chinese Academy of Sciences; grant number: 0950111CS1. Conflict of interest: None. *Correspondence to: Chunxiao Xu, Institute of Electrical Engineering, Chinese Academy of Sciences, Zhongguancun, Beijing, 100190, P. R. China. E-mail: [email protected] Received for review 14 January 2015; Accepted 21 May 2015 DOI: 10.1002/bem.21927 Published online 11 June 2015 in Wiley Online Library (wileyonlinelibrary.com).
Arabidopsis in Near-Null Magnetic Field
field, suggesting that the function of CRY was conserved in different species [Gegear et al., 2010; Foley et al., 2011]. We previously reported that Arabidopsis flowering in a near-null magnetic field was delayed compared to that of plants in the local geomagnetic field in white light under 16 h light and 8 h dark condition, suggesting that near-null magnetic field suppressed Arabidopsis flowering [Xu et al., 2012]. In addition, we found that blue light-dependent phosphorylation of CRY weakened and dephosphorylation of CRY enhanced in Arabidopsis in near-null magnetic field, implying this magnetic field affected the function of CRY [Xu et al., 2014]. Previous research confirmed that CRY activation was blue light-dependent, and magnetic field effect on photo-induced flavin-tryptophan radical pairs in Arabidopsis CRY1 also required blue light, suggesting that magnetic field effect on the function of CRY was mediated by blue light [Yu et al., 2007; Maeda et al., 2012]. Therefore, it is possible that light change alters the effect of near-null magnetic field on Arabidopsis flowering. To test whether light alters the effect of near-null magnetic field on Arabidopsis flowering, we grew Arabidopsis seedlings in near-null magnetic field and local geomagnetic field under blue or red light with different light cycle and PPFD. Arabidopsis flowering was analyzed. Arabidopsis thaliana Columbia ecotype Col-4 (Lehle seeds, Round Rock, TX) was used for experiments. The CRY1/CRY2 mutant [Mockler et al., 1999] used in this study was of Col stock. Surface sterilized seeds were sown on a 1:2 mixture of peat moss and vermiculite in quadrate plastic plates (20 cm inside) and maintained at 4 8C in darkness for 2 days for seed germination consistency. Low-temperaturetreated seeds were then illuminated with white light (30 mmol/m2/s) for 12 h to promote germination, and grown in near-null magnetic field and local geomagnetic field illuminated with blue or red light at 21 0.5 8C. Magnetic field generating equipment and magnetic field treatments of Arabidopsis plants were as described previously [Xu et al., 2013]. Overhead light was provided by light emitting diodes (LEDs) placed 40 cm above the central location of the magnetic field generating equipment. These provided homogeneous light intensity for growth of Arabidopsis seedlings by using diffusers between lights and plants. To test light cycle effect on Arabidopsis flowering, Arabidopsis seedlings were grown in 10 mmol/m2/s blue (460 nm) or red light (650 nm) under continuous light, 12 h L/ 12 h D (24 h period) and 6 h L/6 h D (12 h period) conditions. We grew Arabidopsis seedlings in 10, 20,
477
and 30 mmol/m2/s blue or red lights under a 6 h L/6 h D (12 h period) condition to research the effect of light intensity on Arabidopsis flowering. Flowering times of Arabidopsis were measured as described in Mockler et al. [1999]. When grown in 10 mmol/m2/s blue light, flowering of Arabidopsis plants in near-null magnetic field was different under different light cycles. In continuous light and 12 h L/12 h D conditions, flowering time of Arabidopsis wild-type plants in near-null magnetic field did not show significant difference from that of plants in local geomagnetic field (Fig. 1a). However, in the 6 h L/6 h D condition, flowering time of Arabidopsis wild-type plants in near-null magnetic field was delayed significantly compared to that of controls (Fig. 1a). These results indicated that the effect of near-null magnetic field on Arabidopsis flowering was affected by light cycle change, and the significant effect of near-null magnetic field on Arabidopsis flowering was shown in the shorter light
Fig. 1. a: Flowering time of Arabidopsis plants in near-null magnetic field (N) and local geomagnetic field (G) under three different blue light cycles. Data are means SE of four independent experiments. PPFD of light was 10 mmol/m 2 /s. Significance levels for t-test: P < 0.01. CL: continuous light. b: Flowering time of Arabidopsis plants in near-null magnetic field (N) and local geomagnetic field (G) under 10, 20, or 30 mmol/m2 /s blue light with 6 h L/6 h D cycle. Data are means SE of four independent experiments. Significance levels for t-test: P < 0.01. Bioelectromagnetics
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cycle. The flowering time of CRY1/CRY2 mutants in near-null magnetic field did not show significant difference from local geomagnetic field control in three detected light cycles (Fig. 1a). These results suggested that CRY was involved in suppression of Arabidopsis flowering by near-null magnetic field. Furthermore, we grew Arabidopsis plants in 20 and 30 mmol/m2/s lights under 6 h L/6 h D condition, and found that flowering time of Arabidopsis wild-type plants in near-null magnetic field did not show a significant difference from that of controls, indicating that change of light intensity altered the effect of nearnull magnetic field on Arabidopsis flowering (Fig. 1b). Also, flowering time of CRY1/CRY2 mutants in near-null magnetic field did not show any difference from local geomagnetic field control under detected light intensities (Fig. 1b). In red light, flowering time of Arabidopsis wildtype plants in near-null magnetic field did not show significant difference from that of plants in local geomagnetic field under three detected light cycles and intensities, indicating that near-null magnetic field did not affect Arabidopsis flowering in red light (Fig. 2). Also, the flowering time of CRY1/CRY2 mutants in the near-null magnetic field did not show any difference from the local geomagnetic field control in three detected light cycles and intensities (Fig. 2). These results suggested that the near-null magnetic field did not affect red light receptor involved Arabidopsis flowering. In our present study, we found that suppression of Arabidopsis flowering by near-null magnetic field was shown in the shorter blue light cycle. It was reported that CRY activation depended on blue light, and the activated CRY would be converted to the inactivated state in dark condition [Yu et al., 2007]. Shortening the blue light cycle provided more chances to convert CRY between active and inactive states. Moreover, photo-induced flavin-tryptophan radical pairs in Arabidopsis CRY1 could be affected by magnetic field [Maeda et al., 2012]. Phosphorylation and dephosphorylation of CRY in Arabidopsis were affected by near-null magnetic field [Xu et al., 2014]. Shortening of blue light cycle provided better chances for near-null magnetic field to affect the function of CRY, and, therefore, Arabidopsis flowering. We also found near-null magnetic field effect on Arabidopsis flowering was not significantly shown in blue light with higher intensity. Increase of PPFD of blue light could enhance the function of CRY [Shalitin et al., 2002, 2003]. Thus, we speculate that increase of blue light intensity overcomes the effect of near-null magnetic field on CRY-involved flowering. However, data on the relation between blue light intensity and Bioelectromagnetics
Fig. 2. a: Flowering time of Arabidopsis plants in near-null magnetic field (N) and local geomagnetic field (G) under three different red light cycles. Data are means SE of four independent experiments. PPFD of light was 10 mmol/m2 /s. CL: continuous light. b: Flowering time of Arabidopsis plants in the near-null magnetic field (N) and local geomagnetic field (G) under 10, 20, or 30 mmol/m 2 /s red light with 6 h L/6 h D cycle. Data are means SE of four independent experiments.
Arabidopsis flowering are deficient so far [Yu et al., 2010]. Further research is necessary to demonstrate the effect of blue light intensity on Arabidopsis flowering, and the extent of the effect of near-null magnetic field on the function of CRY. ACKNOWLEDGMENTS We thank Lin Chentao (Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles) for supplying of Arabidopsis seeds. REFERENCES Foley LE, Gegear RJ, Reppert SM. 2011. Human CRY exhibits light-dependent magnetosensitivity. Nat Commun http://dx.doi.org/10.1038/ncomms1364. [Last accessed 10 Jan 2015].
Arabidopsis in Near-Null Magnetic Field Gegear RJ, Casselman A, Waddell S, Reppert SM. 2008. CRY mediates light-dependent magnetosensitivity in Drosophila. Nature 454:1014–1018. Gegear RJ, Foley LE, Casselman A, Reppert SM. 2010. Animal CRYs mediate magnetoreception by an unconventional photochemical mechanism. Nature 463:804–807. Levy YY, Dean C. 1998. The transition to flowering. Plant Cell 10:1973–1990. Lin C. 2000. Photoreceptors and regulation of flowering time. Plant Physiol 123:39–50. Maeda K, Robinson AJ, Henbest KB, Hogben HJ, Biskup T, Ahmad M, Schleicher E, Weber S, Timmel CR, Hore PJ. 2012. Magnetically sensitive light-induced reactions in CRY are consistent with its proposed role as a magnetoreceptor. Proc Natl Acad Sci USA 109:4774–4779. Mockler TC, Guo H, Yang H, Duong H, Lin C. 1999. Antagonistic actions of Arabidopsis CRYs and phytochrome B in the regulation of floral induction. Development 126:2073– 2082. Mockler T, Yang H, Yu X, Parikh D, Cheng Y, Dolan S, Lin C. 2003. Regulation of photoperiodic flowering by Arabidopsis photoreceptors. Proc Natl Acad Sci USA 100:2140–2145. Ritz T, Adem S, Schulten K. 2000. A model for photoreceptorbased magnetoreception in birds. Biophys J 78:707–718.
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Shalitin D, Yang H, Mockler TC, Maymon M, Guo H, Whitelam GC, Lin C. 2002. Regulation of Arabidopsis CRY 2 by blue-light-dependent phosphorylation. Nature 417: 763–767. Shalitin D, Yu X, Maymon M, Mockler T, Lin C. 2003. Blue light-dependent in vivo and in vitro phosphorylation of Arabidopsis CRY 1. Plant Cell 15:2421–2429. Xu C, Yin X, Lv Y, Wu C, Zhang Y, Song T. 2012. A near-null magnetic field affects CRY-related hypocotyl growth and flowering in Arabidopsis. Adv Space Res 49:834–840. Xu C, Wei S, Lu Y, Zhang Y, Chen C, Song T. 2013. Removal of the local geomagnetic field affects reproductive growth in Arabidopsis. Bioelectromagnetics 34:437–442. Xu C, Lv Y, Chen C, Zhang Y, Wei S. 2014. Blue light-dependent phosphorylations of CRYs are affected by magnetic fields in Arabidopsis. Adv Space Res 53:1118–1124. Yu X, Shalitin D, Liu X, Maymon M, Klejnot J, Yang H, Lopez J, Zhao X, Bendehakkalu KT, Lin C. 2007. Derepression of the NC80 motif is critical for the photoactivation of Arabidopsis C RY2. Proc Natl Acad Sci USA 104:7289– 7294. Yu X, Liu H, Klejnot J, Lin C. 2010. The CRY blue light receptors. The Arabidopsis Book 8:e0135. DOI: 10.1199/ tab.0135
Bioelectromagnetics
