Phototropism in Arabidopsis

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== Introduction ==
 
== Introduction ==
  
Being sessile organisms, plants posses various mechanisms to react to different and changing environmental stimuli. One of these mechanisms allows plants to adjust their growth direction to the direction of incoming blue light. This ''phototropic response'' involves sensing of light by photoreceptors, here mainly the membrane-associated proteins phot1 and phot2 [10], redirection of the flux of the hormone auxin [1, 3, 5, 10, 11], as well as other downstream signaling events [2, 4, 6, 7, 9, 12]. Although these key players in phototropism in ''Arabidopsis thaliana'' are known, detailed means of interaction remain hidden.
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Being sessile organisms, plants posses various mechanisms to react to different and changing environmental stimuli. One of these mechanisms allows plants to adjust their growth direction to the direction of incoming blue light. This ''phototropic response'' involves sensing of light by photoreceptors, here mainly the membrane-associated proteins phot1 and phot2 <cite>kk2006a</cite>, redirection of the flux of the hormone auxin <cite>bbpm2004a,etls2006a,nbps2003a,pbbm2004a</cite>, as well as other downstream signaling events <cite>ddri2010a,flds2003a,ikmn2008a,hs2007a,lshp2006a,week2008a</cite>. Although these key players in phototropism in ''Arabidopsis thaliana'' are known, detailed means of interaction remain hidden.
  
The current view on phototropism can be summarized as follows: phototropism is a blue light- initiated process with its response being fluence rate dependent. For simplicity, here only low fluence rates of maximally 0.1 μmol m<sup>-2</sup>s<sup> -1</sup> are considered—a scenario in which the phototropic response depends mostly on the activity of the photo receptor phot1. Under these fluence conditions, the second receptor of the same family, phot2, can be neglected. In addition, the two cryptochromes cry1 and cry2 have a mild effect on phototropism [8] but are not further considered here.
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The current view on phototropism can be summarized as follows: phototropism is a blue light- initiated process with its response being fluence rate dependent. For simplicity, here only low fluence rates of maximally 0.1 μmol m<sup>-2</sup>s<sup> -1</sup> are considered—a scenario in which the phototropic response depends mostly on the activity of the photo receptor phot1. Under these fluence conditions, the second receptor of the same family, phot2, can be neglected. In addition, the two cryptochromes cry1 and cry2 have a mild effect on phototropism <cite>kk2006a</cite> but are not further considered here.
  
  
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== References ==
 
== References ==
  
* [1] J. J. Blakeslee, A. Bandyopadhyay, W. A. Peer ans S. N. Makam, and A. S. Murphy. Relocalization of the PIN1 Auxin Efflux Facilitator Plays a Role in Phototropic Responses. Plant Physiol, 134(1):28–31, 2004.
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<biblio>
* [2] M.deCarbonnel,P.Davis,M.R.G.Roelfsema,S.Inoue,I.Schepens,P.Lariguet,M.Geisler,K.Shimazaki,R.Hangarter, and C. Fankhauser. The Arabidopsis PHYTOCHROME KINASE SUBSTRATE2 Protein Is a Phototropin Signaling Element That Regulates Leaf Flattening and Leaf Postitioning. Plant Physiol, 152(3):1391–1405, 2010.
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# bbpm2004a pmid=14730061
* [3] C. A. Esmon, A. G. Tinsley, K. Ljung, G. Sandberg, L. B. Hearne, and E. Liscum. A gradient of auxin and auxin- dependent transcription precedes tropic growth responses. P Natl Acad Sci USA, 103(1):236–241, 2006.
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# ddri2010a pmid=20071603
* [4] K. M. Folta, E. J. Lieg, T. Durham, and E. P. Spalding. Primary Inhibition of Hypocotyl Growth and Phototropism Depend Differently on Phototropin-Mediated Increases in Cytoplasmic Calcium Induced by Blue Light. Plant Physiol, 133(4):1464–1470, 2003.
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# etls2006a pmid=16371470
* [5] J. Friml, J. Wiśniewska, E. Benková, K. Mendgen, and K. Palme. Lateral relocation of auxin efflux regulator PIN3 mediates tropism in Arabidopsis. Nature, 415(6873):806–809, 2002.
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# flds2003a pmid=14645723
* [6] A.HaradaandK.Shimazaki.PhototropinsandBlueLight-dependentCalciumSignalinginHigherPlants.Photochem Photobiol, 83(1):102–111, 2007.
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# hs2007a pmid=16906793
* [7] S. Inoue, T. Kinoshita, M. Matsumoto, K. I. Nakayama, M. Doi, and K. Shimazaki. Blue light-induced autophospho- rylation of phototropin is a primary step for signaling. P Natl Acad Sci USA, 105(14):5626–5631, 2008.
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# ikmn2008a pmid=18378899
* [8] M. Kimura and T. Kagawa. Phototropin and light-signaling in phototropism. Curr Opin Plant Biol, 9(5):503–508, 2006.
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# kk2006a pmid=16870491
* [9] P. Lariguet, I Schepens, D. Hodgson, U. V. Pedmale, M. Trevisan, C. Kami, M. de Carbonnel, J. M. Alonso, J. R. Ecker, E. Liscum, and C. Fankhauser. PHYTOCHROME KINASE SUBSTRATE 1 is a phototropin 1 binding protein required for phototropism. P Natl Acad Sci USA, 103(26):10134–10139, 2006.
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# lshp2006a pmid=16777956
* [10] B. Noh, A. Bandyopadhyay, W. A. Peer, E. P. Spalding, and A. S. Murphy. Enhanced gravi- and phototropism in plant mdr mutants mislocalizing the auxin efflux protein PIN1. Nature, 423(6943):999–1002, 2003.
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# nbps2003a pmid=12827205
* [11] W. A. Peer, A. Bandyopadhyay, J. J. Blakeslee, S. N. Makam, R. J. Chen, P. H. Masson, and A. S. Murphy. Variation in Expression and Protein Localization of the PIN Family Auxin Efflux Facilitator Proteins in Flavonoid Mutants with Altered Auxin Transport in Arabidopsis thaliana. Plant Cell, 16(7):1898–1911, 2004.
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# pbbm2004a pmid=15208397
* [12] Y.-L. Wan, W. Eisinger, D. Ehrhardt, U. Kubitscheck, F. Baluska, and W. Briggs. The Subcellular Localization and Blue-Light-Induced Movement of Phototropin 1-GFP in Etiolated Seedlings of Arabidopsis thaliana. Mol Plant, 1 (1):103–117, 2008.
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# week2008a pmid=20031918
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</biblio>

Revision as of 11:08, 21 August 2012


Introduction

Being sessile organisms, plants posses various mechanisms to react to different and changing environmental stimuli. One of these mechanisms allows plants to adjust their growth direction to the direction of incoming blue light. This phototropic response involves sensing of light by photoreceptors, here mainly the membrane-associated proteins phot1 and phot2 [1], redirection of the flux of the hormone auxin [2, 3, 4, 5], as well as other downstream signaling events [6, 7, 8, 9, 10, 11]. Although these key players in phototropism in Arabidopsis thaliana are known, detailed means of interaction remain hidden.

The current view on phototropism can be summarized as follows: phototropism is a blue light- initiated process with its response being fluence rate dependent. For simplicity, here only low fluence rates of maximally 0.1 μmol m-2s -1 are considered—a scenario in which the phototropic response depends mostly on the activity of the photo receptor phot1. Under these fluence conditions, the second receptor of the same family, phot2, can be neglected. In addition, the two cryptochromes cry1 and cry2 have a mild effect on phototropism [1] but are not further considered here.


Open Questions

Considering the fact that during phototropism a lateral auxin gradient with its maximum on the shaded side is formed, the question arises how it is possible that such a gradient is established. Here, it is of special interest why the maximum of the gradient is located on the shaded side since the original blue light stimulus is applied to the opposite side and photo-activation seems to be positively fluence correlated. Still, one can argue that the light absorption of a tissue like a dark grown hypocotyl (with a diameter of about 250μm) hardly absorbs any light but then one would need to question why a gradient is formed at all.

In the course of this project, it is planned to investigate this gradient formation relying on both, experimental techniques as well as computational modeling, collaborating with the groups of Richard Smith and Christian Fankhauser as part of the Plant Growth project from SystemsX.ch.

References

  1. Kimura M and Kagawa T. Phototropin and light-signaling in phototropism. Curr Opin Plant Biol 2006 Oct; 9(5) 503-8. doi:10.1016/j.pbi.2006.07.003 pmid:16870491. PubMed HubMed [kk2006a]
  2. Blakeslee JJ, Bandyopadhyay A, Peer WA, Makam SN, and Murphy AS. Relocalization of the PIN1 auxin efflux facilitator plays a role in phototropic responses. Plant Physiol 2004 Jan; 134(1) 28-31. doi:10.1104/pp.103.031690 pmid:14730061. PubMed HubMed [bbpm2004a]
  3. Esmon CA, Tinsley AG, Ljung K, Sandberg G, Hearne LB, and Liscum E. A gradient of auxin and auxin-dependent transcription precedes tropic growth responses. Proc Natl Acad Sci U S A 2006 Jan 3; 103(1) 236-41. doi:10.1073/pnas.0507127103 pmid:16371470. PubMed HubMed [etls2006a]
  4. Noh B, Bandyopadhyay A, Peer WA, Spalding EP, and Murphy AS. Enhanced gravi- and phototropism in plant mdr mutants mislocalizing the auxin efflux protein PIN1. Nature 2003 Jun 26; 423(6943) 999-1002. doi:10.1038/nature01716 pmid:12827205. PubMed HubMed [nbps2003a]
  5. Peer WA, Bandyopadhyay A, Blakeslee JJ, Makam SN, Chen RJ, Masson PH, and Murphy AS. Variation in expression and protein localization of the PIN family of auxin efflux facilitator proteins in flavonoid mutants with altered auxin transport in Arabidopsis thaliana. Plant Cell 2004 Jul; 16(7) 1898-911. doi:10.1105/tpc.021501 pmid:15208397. PubMed HubMed [pbbm2004a]
  6. de Carbonnel M, Davis P, Roelfsema MR, Inoue S, Schepens I, Lariguet P, Geisler M, Shimazaki K, Hangarter R, and Fankhauser C. The Arabidopsis PHYTOCHROME KINASE SUBSTRATE2 protein is a phototropin signaling element that regulates leaf flattening and leaf positioning. Plant Physiol 2010 Mar; 152(3) 1391-405. doi:10.1104/pp.109.150441 pmid:20071603. PubMed HubMed [ddri2010a]
  7. Folta KM, Lieg EJ, Durham T, and Spalding EP. Primary inhibition of hypocotyl growth and phototropism depend differently on phototropin-mediated increases in cytoplasmic calcium induced by blue light. Plant Physiol 2003 Dec; 133(4) 1464-70. doi:10.1104/pp.103.024372 pmid:14645723. PubMed HubMed [flds2003a]
  8. Inoue S, Kinoshita T, Matsumoto M, Nakayama KI, Doi M, and Shimazaki K. Blue light-induced autophosphorylation of phototropin is a primary step for signaling. Proc Natl Acad Sci U S A 2008 Apr 8; 105(14) 5626-31. doi:10.1073/pnas.0709189105 pmid:18378899. PubMed HubMed [ikmn2008a]
  9. Harada A and Shimazaki K. Phototropins and blue light-dependent calcium signaling in higher plants. Photochem Photobiol 2007 Jan-Feb; 83(1) 102-11. doi:10.1562/2006-03-08-IR-837 pmid:16906793. PubMed HubMed [hs2007a]
  10. Lariguet P, Schepens I, Hodgson D, Pedmale UV, Trevisan M, Kami C, de Carbonnel M, Alonso JM, Ecker JR, Liscum E, and Fankhauser C. PHYTOCHROME KINASE SUBSTRATE 1 is a phototropin 1 binding protein required for phototropism. Proc Natl Acad Sci U S A 2006 Jun 27; 103(26) 10134-9. doi:10.1073/pnas.0603799103 pmid:16777956. PubMed HubMed [lshp2006a]
  11. Wan YL, Eisinger W, Ehrhardt D, Kubitscheck U, Baluska F, and Briggs W. The subcellular localization and blue-light-induced movement of phototropin 1-GFP in etiolated seedlings of Arabidopsis thaliana. Mol Plant 2008 Jan; 1(1) 103-17. doi:10.1093/mp/ssm011 pmid:20031918. PubMed HubMed [week2008a]
All Medline abstracts: PubMed HubMed