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Phototropins are photoreceptor proteins (more specifically, flavoproteins) that mediate phototropism responses in higher plants. Phototropins can be found throughout the leaves of a plant. Along with cryptochromes and phytochromes they allow plants to respond and alter their growth in response to the light environment. Phototropins may also be important for the opening of stomata[1] and the movement of chloroplasts. These blue light receptors are seen across the entire green plant lineage. When Phototropins are hit with blue light, they induce a signal transduction pathway that alters the plant cells' functions in different ways.

Phototropins are part of the phototropic sensory system in plants that causes various environmental responses in plants. Phototropins specifically will cause stems to bend towards light[2] and stomata to open.[3] Phototropins have been shown to impact the movement of chloroplast inside the cell.[4][5] In addition phototropins mediate the first changes in stem elongation in blue light prior to cryptochrome activation.[6] Phototropin is also required for blue light mediated transcript destabilization of specific mRNAs in the cell.[7] They are present in the guard cell.


  1. ^ Smith, Garland (2010). Fundamentals of Biomolecular Botany (2 ed.). Fisher Press. p. 340.
  2. ^ Price (2009). Molecular Basis of Botanical Biology. Phoenix Publishing. p. 213.
  3. ^ Price (2009). Molecular Basis of Botanical Biology. Phoenix Publishing. p. 213.
  4. ^ Wada M, Kagawa T, Sato Y (2003). "Chloroplast movement". Annu Rev Plant Biol. 54: 455–68. doi:10.1146/annurev.arplant.54.031902.135023. PMID 14502999.
  5. ^ DeBlasio SL, Luesse DL, Hangarter RP (September 2005). "A plant-specific protein essential for blue-light-induced chloroplast movements". Plant Physiol. 139 (1): 101–14. doi:10.1104/pp.105.061887. PMC 1203361. PMID 16113226.
  6. ^ Folta, Kevin (2001). "Unexpected Roles for Cryptochrome 2 and Phototropin Revealed by High-resolution Analysis of Blue Light-mediated Hypocotyl Growth Inhibition". The Plant Journal. 26.5 (5): 471–78. doi:10.1046/j.1365-313x.2001.01038.x.
  7. ^ Brighton; et al. (2006). "Role of phototropin in the differential expression of blue light mediated mRNAs". International Journal of Molecular Botany. 72 (54): 672–691.

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