Unique insight into the interior of the Arabidopsis photosynthesis
machine

Date:
August 17, 2021
Source:
Umea University
Summary:
Researchers have, with the help of cryogenic electron microscopy,
succeeded in producing a high-resolution image of photosystem
II - the central complex of photosynthesis - of the model plant
Arabidopsis. The enormous complex is responsible for the vital
oxygen production in photosynthesis that once made life possible
on our planet.



FULL STORY ==========================================================================
For the first time, Umeaa researchers have, with the help of cryogenic
electron microscopy, succeeded in producing a high-resolution image
of photosystem II - - the central complex of photosynthesis -- of the
model plant Arabidopsis. The enormous complex is responsible for the
vital oxygen production in photosynthesis that once made life possible
on our planet. The study is published in Scientific Reports.


==========================================================================
"The structure gives us detailed information about the various cofactors
such as chlorophyll and the lipid molecules in photosystem II. We have
also managed to show exactly where and how detergents bind and affect
the stability of the complex," says Wolfgang Schro"der, professor at
the Department of Chemistry at Umeaa University Sweden, who led the study.

The plant researchers' "experimental rat" has for the past 25 years been
the plant thale cress/mouse-ear cress Arabidopsis thaliana. The reason
for this is that this "weed" grows rapidly even at our northern latitudes
in Sweden and in 2000, researchers succeeded in sequencing all its genes.

At the heart of the photosynthetic process is the Photosystem II
complex. It contains almost 30 different proteins and a number of
cofactors such as different pigments and metals and it is without
any doubt one of the largest complexes in plant chloroplasts. The now
published structure from this study has the same high-resolution as the
two previous structures obtained from spinach and pea, which for the
first time enables a comparison of plants' photosystem II complex with
the same level of detail.

"I have worked with this complex since I became a PhD student in plant
protein chemistry at Lund University in 1983," says Wolfgang Schro"der. "I remember that as a doctoral student I joked at the coffee break "think
if you could dive into photosystem II and look around." Today with new technology and my extremely talented doctoral student Andre' Grac,a and
my two fantastic research colleagues Michael Hall and Karina Persson, we
have now been able to do this." The technology that the researchers have
used is called cryogenic electron microscopy (Nobel Prize in Chemistry
2017) and it briefly means that biological samples are shot down into
liquid ethane (-190 degrees Celsius). Nearly 100,000 two-dimensional EM particle images from random orientations are selected. Using several computational resources, the collection of 2D images can then be used
to reconstruct a three-dimensional structure.

"Additionally, it was extremely exciting to see if our previous
biochemical analyzes of the complex were correct. Usually, the privilege
of publishing structures with this size and resolution is only possible
to larger research teams from different laboratories, as it requires a
lot of data, time and effort. In our case we are four Umeaa researchers
within the network Integrated Structural Biology, ISB, who created this structure so it is "locally" produced research," says Wolfgang Schro"der
with a smile.

The research is mainly funded by the Carl Tryggers Foundation. Data
were collected at Umeaa Core Facility for Electron Microscopy, UCEM,
which is part of the National Microscopy Infrastructure, NMI.

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


========================================================================== Journal Reference:
1. Andre' T. Grac,a, Michael Hall, Karina Persson, Wolfgang
P. Schro"der.

High-resolution model of Arabidopsis Photosystem II reveals the
structural consequences of digitonin-extraction. Scientific Reports,
2021; 11 (1) DOI: 10.1038/s41598-021-94914-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210817111427.htm

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