Phototropism: Bending towards Enlightenment

Whippo, Craig W.; Hangarter, Roger P.

doi:10.1105/tpc.105.039669

Cited by 130 publications

(110 citation statements)

References 104 publications

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“…We therefore reject the hypothesis that cryptochromes do not operate in the absence of phytochromes (9). Although phytochromes modulate phototropic responses (40), the quintuple mutant also retained hypocotyl phototropism mediated by phototropins (Fig. S3).…”

Section: Discussionmentioning

confidence: 64%

Arabidopsis thaliana life without phytochromes

Strasser

Sánchez‐Lamas

Yanovsky

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

172

150

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Plants use light as a source of energy for photosynthesis and as a source of environmental information perceived by photoreceptors. Testing whether plants can complete their cycle if light provides energy but no information about the environment requires a plant devoid of phytochromes because all photosynthetically active wavelengths activate phytochromes. Producing such a quintuple mutant of Arabidopsis thaliana has been challenging, but we were able to obtain it in the flowering locus T ( ft ) mutant background. The quintuple phytochrome mutant does not germinate in the FT background, but it germinates to some extent in the ft background. If germination problems are bypassed by the addition of gibberellins, the seedlings of the quintuple phytochrome mutant exposed to red light produce chlorophyll, indicating that phytochromes are not the sole red-light photoreceptors, but they become developmentally arrested shortly after the cotyledon stage. Blue light bypasses this blockage, rejecting the long-standing idea that the blue-light receptors cryptochromes cannot operate without phytochromes. After growth under white light, returning the quintuple phytochrome mutant to red light resulted in rapid senescence of already expanded leaves and severely impaired expansion of new leaves. We conclude that Arabidopsis development is stalled at several points in the presence of light suitable for photosynthesis but providing no photomorphogenic signal.

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Section: Discussionmentioning

confidence: 64%

Arabidopsis thaliana life without phytochromes

Strasser

Sánchez‐Lamas

Yanovsky

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

172

150

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“…Roots need to sense and respond appropriately to a diversity of environmental signals, such as gravity, mechanical impedance, light, humidity, oxygen, and essential nutrients, as well as to allelochemicals exuded from neighboring roots, to develop their optimal form or adapt to their environment conditions (Monshausen and Gilroy, 2009). Although phototropic responses in roots were discovered and analyzed some time ago, knowledge of root phototropism is surprisingly poor when compared with that of root gravitropism (Boonsirichai et al, 2002;Correll and Kiss, 2002;Whippo and Hangarter, 2006;Holland et al, 2009;Takahashi et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

The Signal Transducer NPH3 Integrates the Phototropin1 Photosensor with PIN2-Based Polar Auxin Transport in Arabidopsis Root Phototropism

et al. 2012

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Under blue light (BL) illumination, Arabidopsis thaliana roots grow away from the light source, showing a negative phototropic response. However, the mechanism of root phototropism is still unclear. Using a noninvasive microelectrode system, we showed that the BL sensor phototropin1 (phot1), the signal transducer NONPHOTOTROPIC HYPOCOTYL3 (NPH3), and the auxin efflux transporter PIN2 were essential for BL-induced auxin flux in the root apex transition zone. We also found that PIN2-green fluorescent protein (GFP) localized to vacuole-like compartments (VLCs) in dark-grown root epidermal and cortical cells, and phot1/NPH3 mediated a BL-initiated pathway that caused PIN2 redistribution to the plasma membrane. When dark-grown roots were exposed to brefeldin A (BFA), PIN2-GFP remained in VLCs in darkness, and BL caused PIN2-GFP disappearance from VLCs and induced PIN2-GFP-FM4-64 colocalization within enlarged compartments. In the nph3 mutant, both dark and BL BFA treatments caused the disappearance of PIN2-GFP from VLCs. However, in the phot1 mutant, PIN2-GFP remained within VLCs under both dark and BL BFA treatments, suggesting that phot1 and NPH3 play different roles in PIN2 localization. In conclusion, BL-induced root phototropism is based on the phot1/NPH3 signaling pathway, which stimulates the shootward auxin flux by modifying the subcellular targeting of PIN2 in the root apex transition zone.

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“…A term "heliotropism" is defined as directional motion of some organisms in response to the direction of sunlight (see more Kudo, 1995;Whippo, 2006). The heliotropism from fossil stromatolites were first recognized in early 1960s by pioneer researchers such as Vologdin (1961Vologdin ( , 1963 and Nordeng (1963) who presented evidence of heliotropism in Precambrian branching columnar stromatolite.…”

Section: Discussion On Heliotropismmentioning

confidence: 99%

“…This phenomenon, called as "heliotropism", is particularly and easily identifiable in photosynthetic organisms including plant, aquatic algae and even bacteria (Golubic and Focke, 1978;Kudo, 1995;Whippo, 2006). The term "heliotropism" refers to positive movement of a whole organism or part of an organism toward the direction of increasing intensity of sunlight.…”

Section: Introductionmentioning

confidence: 99%

Possibility for Heliotropism from Inclined Columns of Stromatolites, Socheong Island, Korea

Kong¹,

Lee²

2013

Journal of the Korean earth science society

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Socheong island is a unique island containing Precambrian stromatolites in South Korea. Most of Socheong stromatolites are domes and columns, occurring as 10 cm to 1 m thick stromatolite beds. Lower parts of the stromatolite beds are predominantly composed of domes, but columns increase toward the upper level of stromatolite beds. In many of the stromatolite beds, inclined columns are easily identifiable, which is generally considered as a result of heliotropism. From general lithology, sedimentary structures, inclined angles and distributional pattern, and structural deformation of sedimentary rocks of Socheong island, the inclination of Socheong stromatolites could be better interpreted as a secondary structural deformation probably after formation of stromatolite columns, rather than as a result of heliotropism. However, at this moment, we do not clearly reject heliotropism interpretation for inclined columns of Socheong stromatolites. This is because the original position of stromatolite columns could have been lost if structural deformation had affected the whole sedimentary rocks of Socheong island.

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Phototropism: Bending towards Enlightenment

Cited by 130 publications

References 104 publications

Arabidopsis thaliana life without phytochromes

Arabidopsis thaliana life without phytochromes

The Signal Transducer NPH3 Integrates the Phototropin1 Photosensor with PIN2-Based Polar Auxin Transport in Arabidopsis Root Phototropism

Possibility for Heliotropism from Inclined Columns of Stromatolites, Socheong Island, Korea

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