Chemical and structural analysis of a photoactive vertebrate cryptochrome from pigeon

Computational and biochemical studies implicate the blue-light sensor cryptochrome (CRY) as an endogenous light-dependent magnetosensor enabling migratory birds to navigate using the Earth’s magnetic field. Validation of such a mechanism has been hampered by the absence of structures of vertebrate CRYs that have functional photochemistry. Here we present crystal structures of Columba livia (pigeon) CRY4 that reveal evolutionarily conserved modifications to a sequence of Trp residues (Trp-triad) required for CRY photoreduction. In ClCRY4, the Trp-triad chain is extended to include a fourth Trp (W369) and a Tyr (Y319) residue at the protein surface that imparts an unusually high quantum yield of photoreduction. These results are consistent with observations of night migratory behavior in animals at low light levels and could have implications for photochemical pathways allowing magnetosensing.

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The effect of low light levels on postural stability in older adults with age‐related macular degeneration

Ophthalmic and Physiological Optics ◽

10.1111/opo.12827 ◽

2021 ◽

Author(s):

Mahesh K Dev ◽

Joanne M Wood ◽

Alex A Black

Keyword(s):

Older Adults ◽

Macular Degeneration ◽

Postural Stability ◽

Age Related Macular Degeneration ◽

Low Light ◽

Light Levels ◽

Age Related

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Growth ofPseudotsuga menziesiiandTsuga heterophyllaseedlings along a light gradient: resource allocation and morphological acclimation

Canadian Journal of Botany ◽

10.1139/b97-857 ◽

1997 ◽

Vol 75 (9) ◽

pp. 1424-1435 ◽

Cited By ~ 32

Author(s):

D. Mailly ◽

J. P. Kimmins

Keyword(s):

Leaf Morphology ◽

Biomass Accumulation ◽

Tsuga Heterophylla ◽

Douglas Fir ◽

Western Hemlock ◽

Low Light ◽

Growing Seasons ◽

Light Levels ◽

Light Gradient ◽

Relative Light Intensity

Silvicultural alternatives that differ in the degree of overstory removal may create shady environments that will be problematic for the regeneration of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Gradients of light in the field were used to compare mortality, growth, and leaf morphological acclimation of two conifer species of contrasting shade tolerances: Douglas-fir and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Results after two growing seasons indicated that Douglas-fir mortality occurred mainly at relative light intensity (RLI) below 20%, while western hemlock mortality was evenly distributed along the light gradient. Height, diameter, and biomass of the planted seedlings increased with increasing light for both species but at different rates, and maximum biomass accumulation always occurred in the open. Douglas-fir allocated more resources to stem biomass than western hemlock, which accumulated more foliage biomass. Increases in specific leaf area for Douglas-fir seedlings occurred at RLI ≤ 0.4 and red/far red (R/FR) ratio ≤ 0.6, which appear to be the minimal optimum light levels for growth. Conversely, western hemlock seedlings adjusted their leaf morphology in a more regular pattern, and changes were less pronounced at low light levels. These results, along with early mortality results for Douglas-fir, suggest that the most successful way to artificially regenerate this species may be by allowing at least 20% of RLI for ensuring survival and at least 40% RLI for optimum growth. Key words: light, light quality, leaf morphology, acclimation.

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Characterization of charge-coupled device line and area-array imaging at low light levels

10.1109/isscc.1973.1155159 ◽

1973 ◽

Cited By ~ 14

Author(s):

M. White ◽

D. Lampe ◽

I. Mack ◽

F. Blaha

Keyword(s):

Low Light ◽

Charge Coupled Device ◽

Light Levels ◽

Area Array ◽

Array Imaging

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Signal to noise ratio in speckle interferometry in the photon counting autocorrelation mode at low light levels

Optics Communications ◽

10.1016/0030-4018(79)90098-1 ◽

1979 ◽

Vol 29 (3) ◽

pp. 273-278 ◽

Cited By ~ 6

Author(s):

J.G. Walker

Keyword(s):

Signal To Noise Ratio ◽

Photon Counting ◽

Speckle Interferometry ◽

Signal To Noise ◽

Low Light ◽

Light Levels ◽

Noise Ratio

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Photoinhibition of DCMU-Enhanced Fluorescence in Lake Ontario Phytoplankton

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f87-263 ◽

1987 ◽

Vol 44 (12) ◽

pp. 2144-2154 ◽

Cited By ~ 8

Author(s):

M. Putt ◽

G. P. Harris ◽

R. L. Cuhel

Keyword(s):

Vertical Mixing ◽

Natural Populations ◽

Bright Light ◽

Euphotic Zone ◽

Lake Ontario ◽

Enhanced Fluorescence ◽

Low Light ◽

Light Levels ◽

Phosphorus Status

Measurement of 1-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) enhanced fluorescence (FDCMU) suggested that photoinhibition of photosynthesis was frequently an artifact of in situ bottle incubations in Lake Ontario phytoplankton. In a seasonal study, FDCMU of all populations was depressed by bright light in an incubator. However, when the euphotic zone did not exceed the depth of the mixed layer, vertical transport of phytoplankton into either low-light or dark regions apparently allowed reversal of photoinhibition of FDCMU. Advantages of FDCMU as a bioassay of vertical mixing include rapidity of response time, ease of measurement in the field, and insensitivity of this parameter to changes in phosphorus status of the population. Because of seasonal changes in the photoadaptive response of natural populations, the rate constants and threshold light levels required to cause the response must be determined at each use if the method is to be quantitative.

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