Molecular 'blueprint' illuminates how plants perceive light

Date:
March 30, 2022
Source:
Van Andel Research Institute
Summary:
Plants rely on their ability to sense light for survival. But
unlike animals, plants don't have eyes full of photoreceptors to
capture and convey messages from visual stimuli. Instead, plants are
coated with a network of light-sensing photoreceptors that detect
different wavelengths of light, allowing them to regulate their
lifecycles and adjust to environmental conditions. Now, scientists
have determined the molecular structure of one of these vital
photoreceptors -- a protein known as PhyB -- revealing a wholly
different structure than previously known. The findings may have
implications for agricultural and 'green' bioengineering practices.



FULL STORY ========================================================================== Plants rely on their ability to sense light for survival. But unlike
animals, plants don't have eyes full of photoreceptors to capture
and convey messages from visual stimuli. Instead, plants are coated
with a network of light-sensing photoreceptors that detect different wavelengths of light, allowing them to regulate their lifecycles and
adjust to environmental conditions.


==========================================================================
Now, Van Andel Institute and Washington University scientists have
determined the molecular structure of one of these vital photoreceptors
-- a protein known as PhyB -- revealing a wholly different structure
than previously known. The findings, published today in Nature, may have implications for agricultural and "green" bioengineering practices.

"Photoreceptors, such as PhyB, help plants sense and respond to the
world around them by influencing life-sustaining processes such as
shade avoidance, seed germination, determination of flowering time,
and development of chloroplasts, which convert light into usable
energy," said VAI Professor Huilin Li, Ph.D., co-corresponding author
of the study. "Our new structure sheds light onto how PhyB works and
has potential for a host of applications in agriculture, renewable
energy and even in cellular imaging." Understanding the shape of PhyB
is important because its structure directly impacts how PhyB interacts
with other molecules to communicate shifts in light conditions and to
help plants adapt by driving changes in gene expression.

Previous research on PhyB provided only a truncated snapshot rather than
a detailed rendering of the entire molecule.

To determine their near-atomic resolution image of PhyB, Li and study co- corresponding author Richard D. Vierstra, Ph.D., of Washington University, turned to one of the most studied plants on Earth -- a humble weed called Arabidopsis thaliana.This small flowering plant is an ideal model for
research because it reproduces quickly, is small and is easy to grow.

UsingVAI's high-powered cryo-electron microscope, or cryo-EM, the
research team snapped nearly 1 million particle images of PhyB connected
to its natural chromophore -- a molecule that absorbs a certain color
of light. They then narrowed the images down to 155,000, which they used
to construct the full visualization of PhyB's structure at a near-atomic
level of 3.3 AAngstrom.

Their work revealed a surprise: rather than the parallel structure
described by earlier studies, they found a complicated 3D structure with
both parallel and anti-parallel sections. The findings suggest that PhyB
may amplify small changes in light-sensing chromophore molecules and drastically change its shape in response -- a move that communicates
the availability of light to the plant.

The discovery is the result of more than a decade of collaboration
between Li and Vierstra, and revolutionizes what we know about PhyB and phytochromes, the family of receptors to which PhyB belongs. Until now,
it was believed that PhyB and other phytochromes likely were similar to
those used by single-celled organisms, such as certain bacteria. Today's findings upend that theory and lay the foundations for further studies
into the intricate details of PhyB and phytochrome function.

Hua Li, Ph.D., of VAI and Sethe Burgie, Ph.D., of Washington University
are co- first authors of the study. Zachary T.K. Gannam, Ph.D., of
Washington University also is an author. Cryo-EM data were collected in collaboration with VAI's Cryo-EM Core and the David Van Andel Advanced Cryo-Electron Microscopy Suite.


========================================================================== Story Source: Materials provided by Van_Andel_Research_Institute. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Li, H., Burgie, E.S., Gannam, Z.T.K. et al. Plant phytochrome B
is an
asymmetric dimer with unique signalling potential. Nature, 2022
DOI: 10.1038/s41586-022-04529-z ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220330111324.htm

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