AccessScience | Research Update | Phototropin - 0 views
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Typically, stems show positive phototropism (movement toward the light), whereas roots exhibit negative phototropic movement (away from the source of light).
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Arabidopsis contains two phototropins referred to as phot1 and phot2. Mutants of Arabidopsis lacking both phototropins lose their phototropic responsiveness
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Phototropic response
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phototropins control the movement of chloroplasts
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these responses serve to enhance the photosynthetic
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Phototropins, like photoreceptor pigments associated with mammalian vision, comprise many amino acids (900–1000) that form the main structure of the protein (the apoprotein) to which an accessory chemical cofactor is bound that can absorb light and impart color (the chromophore)
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a small fraction of the receptor pool is rapidly internalized (within minutes) upon blue light irradiation
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Phototropins are typically associated with the plasma membrane
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However, the biological significance
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As light passes through the stem, it becomes progressively diffracted, thereby generating a gradient of phototropin activation across the organ, with the highest level of activity occurring on the irradiated side
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In some plant species, including the fern Adiantum capillus-veneris, phototropism and chloroplast movement are induced by red light as well as blue.
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novel
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The presence of such a hybrid photoreceptor is proposed to enhance light sensitivity and aid the prevalence of species such as ferns in low light conditions
