non-invasive cell imaging method reveals lipid droplet structure
An INRAE-led research coordinated by Marine Froissard, "Cell
Différenciation and Polarity" Team in collaboration
with Yann Gohon équipe "Dynamics
and Structure of Lipid bodies" has developed a new multimodal
imaging method that combines different microscopy techniques used at
synchrotron (France) and the ALBA
synchrotron (Spain). This method was used to gather complementary information
about the composition and structure of lipid droplets in yeast cells.
One of its advantages? It does not employ any chemical markers or fixing
agents, which can potentially damage cells. The results of this research
were published on May 4, 2020, in Journal of Synchrotron Radiation.
The body is made up of different
organs, which all have crucial roles. In the same way, the cells of
complex organisms are composed of different organelles with distinct
functions, ensuring cell viability. Among these organelles are lipid
droplets. Lipid droplets have been the focus of intense study because
they play a role in several diseases, including diabetes and obesity.
The lipids found in the droplets are of interest to the food industry
(e.g., for making vegetable oils), the green chemistry industry (e.g.,
for making biodiesel), and the cosmetics industry (e.g., for making
soaps and lotions containing vegetable oils). Diverse lipids are present
within the droplets, although triglycerides and cholesterol esters predominate
and are responsible for droplet structure. Thus, clarifying the structure
and composition of lipid droplets has important practical consequences.
Current methods for studying the internal
structure of lipid droplets destroy cells. These methods have led to
major discoveries about the structure and composition of individual
droplets or droplets observed in sectioned cells. It is now necessary
to develop new imaging tools to more comprehensively study how the droplets
function and interact with other organelles within intact cells.
A new non-invasive cell imaging
An INRAE-led research team developed a new non-invasive cell imaging
method by adapting and combining two imaging techniques previously used
to study plant and animal cells. This new method was employed to study
cells of baker's yeast (Saccharomyces cerevisiae).
First, researchers used cryo soft X-ray tomography (employed at the
ALBA synchrotron) to analyse yeast cells exposed to ultrarapid freezing
(i.e., vitrified yeast cells). This x-ray-based technique makes it possible
to study the internal architecture of cells at the nanometric scale
(i.e., one billionth of a metre). More specifically, the technique can
reveal organelle arrangements and interactions. Lipid droplets strongly
absorb x-rays and can thus be clearly seen in the resulting images.
Second, researchers used deep-UV imaging
(employed at the SOLEIL synchrotron). This technique does not require
any special preliminary procedures and allows researchers to observe
living cells at micrometric to nanometric scales (i.e., from one millionth
to one billionth of a metre). Consequently, it can be used to observe
the dynamics of internal cellular processes. The challenge was to adapt
this technique for use on yeast cells, which are 10 times smaller than
plant or animal cells.
Revealing the internal structure
of cells ten times smaller than plant or animal cells
Cryo soft X-ray tomography showed that the structure of lipid droplets
changed depending on their composition. Deep-UV imaging provided information
about the structure of and contact between organelles in a living yeast
cell at a scale of around 100 nanometres, without the need for any chemical
markers. The researchers also developed specific procedures for combining
different UV imaging techniques (i.e., based on the transmittance and
fluorescence of tryptophan and tyrosine, two amino acids) with a view
to studying living cells.
By using cryo soft X-ray tomography
and deep-UV imaging in tandem, the researchers were able to obtain complementary
information on cells at the micrometric to nanometric scale. The x-ray-based
imaging technique can be used to explore the detailed structure of cell
organelles. In contrast, the UV-based imaging technique can be used
to characterise biological processes within cells (e.g., cell division);
determine the fate of molecules that originate from outside the cell;
and examine cellular responses to stress. This new non-invasive cell
imaging method could also be used to analyse other types of cells, notably
plant or animal cells, and could thus prove beneficial to other synchrotron
researchers and biologists in general. The method will make it easier
to build a new organelle atlas in living cells.
The SOLEIL synchrotron and its relationship with INRAE
s a large research facility where scientists study matter via its interactions
with light. At the SOLEIL synchrotron, researchers can exploit a diversity
of spectroscopic methods that utilise a wide range of the electromagnetic
spectrum, from the far infrared to UV to hard x-rays.
INRAE is linked to SOLEIL by two engineers, who dedicate
themselves to SOLEIL-specific research; a research coordinator; and
the scientific advisory board of INRAE users at SOLEIL (the Conseil
Scientifique d’Utilisateurs [CSU]). INRAE scientists who want
to carry out research at SOLEIL must first send their project proposals
to the CSU, which inventories potential projects. It also helps researchers
refine their proposals, choose the appropriate program committee, and
reduce research overlap. The proposal is then submitted via the Sunset
platform. Calls for proposals take place twice a year: the deadlines
are February 15 and September 15.
Institut Jean-Pierre Bourgin (INRAE, AgroParisTech)
Associated Department: TRANSFORM
Associated Centre :
Frédéric Jamme, Bertrand Cinquin, Yann Gohon, Eva Pereiro,
Matthieu Réfrégiers et Marine Froissard, Synchrotron multimodal
imaging in a whole cell reveals lipid droplet core organization, Journal
of Synchrotron radiation, Mai 2020
DOI : https://doi.org/10.1107/S1600577520003847
First evidence that extracellular nanofilaments manipulate cell shape
Until now, it was thought that the shape of plant cells was determined
only by the hydrostatic pressure within the cells exerted against
the cell wall. Scientists from the team "Primary
cell wall", in collaboration with researchers of the University
of Cambridge and the Caltech/Howard
Hughes Medical Institute,
have discovered new filamentous structures within plant cell walls
that influence cell growth and help build complex three-dimensional
cell shapes. Published in Science the 27th February 2020, these results
could also have implications in the animal kingdom and in future to
be an inspiration for development of new smart materials.
Combining two types of high-performance
microscopes, the researchers identified pectin nanofilaments aligned
in columns along the edge of the cell walls of plants. The filaments,
which are 1,000 times thinner than a human hair, had only ever been
synthesised in a lab, but never observed in nature until now.
These revelations about the cell
wall structure are crucial for understanding how plants form their
complex shapes and will help increase understanding of plant immunity
and adaptation to changing environments, and possibly inspire future
development of biofuels, agriculture, and even building smart, self-expanding
It might look like a uniform surface of green, but place a typical
leaf under a microscope and an intricate patchwork of irregular-shaped
cells fitting together perfectly like a jigsaw puzzle is revealed.
Each of these cells on the surface of a leaf, called pavement cells,
has its own unique shape and continues to expand and change shape
as the leaf grows.
The current "textbook" thinking about how these unusual
wavy-shaped cells are formed is that the internal pressure within
the cell (turgor) pushes against the rigid cell wall that surrounds
each cell to define its final shape. Weaker parts of the wall expand
further, like air pressure forcing weaker areas of a balloon to expand
Published today in the journal Science, researchers from the French
National Research Institute for Agriculture, Food and Environment
(INRAE) together with scientists from the University of Cambridge
and Caltech/Howard Hughes Medical Institute are the first to show
the presence of pectin nanofilament structures. Not only did they
discover these new structures, they also demonstrated that they actively
drive cell shape – and even cell growth – independent
of pressure within the cell.
Before the team’s discovery, pectin was considered a disorganised
gel-like filling material sitting between the long cellulose fibres
in the cell wall. Dr Kalina T. Haas, first author of the paper, who
was working at the University of Cambridge at the time and is now
an INRAE researcher, explains: “Biochemistry is typically
used to study the components of the cell wall, but biochemical analysis
disintegrates the cell wall to extract molecules for further study
and so we do not get a chance to examine the original structure. Conventional
fluorescence microscopes with a resolution of 200 nm aren’t
any help either as the cell wall is only 50-100 nm in width and too
small for this type of microscope to see its detailed structure. To
overcome this, we used two types of cutting-edge microscopy, dSTORM
and cryoSEM, which allowed us to keep the cell wall intact. Together,
these microscopes revealed that pectins do not form a 'jelly', but
create a well organised nanoscaled colonnade (sequence of columns)
along the edge of the cell wall.”
The cryo Scanning Electron Microscope (cryoSEM, very low temperature)
developed at the Sainsbury Laboratory at the University of Cambridge
captured the very first images of these pectin filaments. Dr Raymond
Wightman, Imaging Core Facility Manager at the Sainsbury
Laboratory, said: “It was in a lab 40 years ago that
chemists first demonstrated that pectin might form filaments, but
these had never been observed in nature. The cryoSEM provided us with
the very first images of pectin as filamentous structures and the
super-high resolution light microscope called dSTORM confirmed that
what we were seeing was actually pectin structures. No single microscope
by itself could have confirmed these results.”
Dr Kalina T. Haas and Dr Alexis Peaucelle at INRAE adapted the MRC/LMB’s
dSTORM microscope to analyse the leaf cells of Arabidopsis thaliana
(thale cress) at a high resolution of 20-40 nm. They found that a
single type of chemical change (methyl group removal) in the pectin
nanofilament triggers the filaments to swell and expand radially by
around 40%. This swelling causes buckling of the cell wall, which
then initiates the growth and formation of the unusual wavy-shaped
Dr Peaucelle explained: “This is related to a change in
the packaging of pectin polymers inside the nanofilament from a compact
to a loose lattice. Such self-expansion of the cell wall components,
coupled with their local orientation, can drive the emergence of complex
shapes. A computer model found the small change in size that accompanies
a modified nanofilament is enough to make the jigsaw puzzle cell shape.
Furthermore, these shape changes did not need the force of turgor
within the modelled cells.”
Further research will be required to determine what contribution turgor
pressure and the cellulose in the cell wall play in determining cell
shape. The team think it likely that turgor pressure and cellulose
work alongside pectin nanofilaments to help to maintain shape.
Dr Peaucelle continued: “We also found that the puzzle-shape
of plant epidermal cells is very ordered. When we sonified the images,
we observed that their shapes are organised in waves similar to that
produced by a musical instrument. As an example, we used different
cells to create notes from a chromatic scale and then play ‘The
Blue Danube’ by J. Strauss with them. It is extraordinary that
through increasing our understanding of how the epidermal cells form
their wavy pattern, we also confirmed that pectin is involved in the
growth process. This highlights how little we know about something
so vital for sustaining our society as plant growth. I envisage further
discoveries in plant and human health will come as more attention
is given to the extracellular matrix surrounding cells, thanks to
the new generation of high-resolution microscopes. Although animal
cells are not surrounded by cell walls, they are surrounded by an
extracellular matrix of proteins and sugars, which may similarly guide
Authors conclude, by saying that self-expansion related function may
be present in different kingdoms. Other extracellular matrix polysaccharides
such as carrageenan of red algae, alginate of brown algae, or even
hyaluronic acid in Animalia may play a similar role.
Institut Jean-Pierre Bourgin (INRAE, AgroParisTech)
Associated Department: BAP
Kalina T. Haas, Raymond Wightman, Elliot M. Meyerowitz et Alexis Peaucelle
(2020) Pectin homogalacturonan nanofilament expansion drives
morphogenesis in plant epidermal cells, Science, Vol. 367,
Issue 6481, pp. 1003-1007
INRAE Press release
Pectin homogalacturonan nanofilament expansion drives morphogenesis
in plant epidermal cells.
27th Frebuary 2020
Updated 2nd March 2020
Book: Abscisic Acid in plants
Editors, Mitsunori Seo et Annie
Abscisic acid in plants, Volume 92,
the latest release in the Advances in Botanical Research series
is a compilation of the current state-of-the-art on the topic. Chapters
in this new release comprehensively describe latest knowledge on how
ABA functions as a plant hormone. They cover topics related to molecular
mechanisms as well as the biochemical and chemical aspects of ABA
action: hormone biosynthesis, catabolism, transport, perception, signaling
in plants, seeds and in response to biotic and abiotic stresses, hormone
evolution and chemical biology, and much more.
Plant growth and human diseases: deciphering common regulators
From plant adaptation to the
environment to human disease control, the
team of Christian Meyer
Use, Transport and signaling" in collaboration with Belgium
teams of the Vlaams Instituut voor Biotechnologie (VIB), found common
regulators to plants and animals. They show that a mutated protein
(YAK1) allow to counteract the effects of another protein (TOR) consequently
reducing growth and metabolism. published in Cell Reports, their results
open up new perspectives to improve plant growth, human cancer therapy
or neurological diseases.
Found in animals, plants, fungi and yeasts,
the protein « Target Of Rapamycin » (TOR) control many
key biological processes as cell proliferation and metabolic activities.
TOR is an enzyme of kinase type; it means that this enzyme adds a
phosphate on aminoacids of target proteins to regulate its activity
or stabilize it.
TOR activity is increased in numerous
human cancers and its inhibitors can reduce the proliferation of cancers.
Among them, the most famous is rapamycin, an antibiotic discovered
in the 70s and produced by a bacterium found in the Easter Islands
In plants TOR regulates growth and
yield of defense against pathogens. Scientists shown that genetic
mutations of TOR affecting the activity of the protein reduce drastically
growth and slow down the development.
Scientists of the IJPB
team of Christian Meyer "Nitrogen
Use, Transport and signaling" in collaboration with Belgium
teams, used the model plant Arabidopsis thaliana to
identify new mutations suppressing the growth and allowing to compensate
TOR defects. Thanks to this strategy another kinase, YAK1 (Yet Another
Kinase 1) also existing in yeast, was identified. The mutated YAK1
allow to plants already affected in TOR activity to recover a bigger
size and a better growth. The metabolic disturbances linked to the
inactivation of TOR are also decreased. Then, YAK1 inactivation by
TOR seams to be necessary to activate the plant growth.
Homologues of the YAK1 kinase do
exit in animals. In human notably, those homologues (including DYRK1A)
are involved among others in symptoms of trisomy 21 or autism.
A better understanding of links between
TOR and YAK1 could improve cultivated plants adaptation performances
to the environment, but also therapies of human diseases linked to
cell proliferation (as cancers) or to neurological development. Indeed,
a hight proportion of genes involved in human cancers do also exist
in Arabidopsis and cell processes associated to cell proliferation
are very similars, for example, in response to some pathogens.
Wild type Arabidopsis
plants (top left) show a very reduced growth when the LST8
protein, a component of the TOR complex, is mutated (top right).
Extra mutations of the kiinase YAK1 supress partially defects
of the plant growth and development (bottom left and right).
The YAK1 kinase is located in the nucleus and cytoplasm of
vegetal cells (in the center, detection of a protein fusion
between YAK1 and a fluorescent marker). Photos IINRA, Céline
||A model of the relationship between TOR,
YAK1 and growth in plants. RAPTOR, LST8 and TOR proteins are
components of the TORC1 complex in Eucaryotes. the reversed
T corresponds to an inhibition. copyright INRA
de presse INRA 06/06/19
Meyer (01 30 83 30 67)
Institut Jean-Pierre Bourgin (INRA, AgroParisTech ; ERL CNRS)
Inra Press Room
(01 42 75 91 86)
Mutations of the AtYAK1 kinase suppress TOR deficiency in
Arabidopsis. Céline Forzanni, Gustavo T.
Duarte, Jelle Van Leene, Gilles Clément, Stéphanie Huguet,
Christine Paysant-Le Roux, Raphaël Mercier, Geert De Jaeger,
Anne-Sophie Leprince, Christian Meyer. Cell Reports. 18 juin 2019.
24th June 2019
Monday 9th March 2020, 2:00 pm
of Munich, Germany
Allocation decisions in Arabidopsis thaliana
Invited by :
compulsory except for INRAE Versailles members up to
Seminars location except
Amphitheatre, Building 10
INRA Centre de Versailles-Grignon
Route de St Cyr (RD10)
F-78026 Versailles Cedex
Page Intranet séminaires IJPB
Workshop Sugar Allocation in Plants
The organization of the Workshop is postponed taking into account
the health situation.
production and crop quality is the result of a number of processes.
One major process is how sugars are allocated over the different
organs after carbon fixation and assimilation in the leaves by photosynthesis.
It depends on a steady-state balance between consumption, storage
and long-distance transport at the level of the cell and the organ.
It is also intricately related to sugar metabolism and homeostasis.
It is also characterized by the trade-offs of plant energetic and
primary metabolism, therefore plant growth, with the responses to
the environment. The most recent discoveries of key factors acting
in the regulation of sugar allocation have recently shed light on
the role of sugars transport in plant adaptation to a range of abiotic
and biotic stresses. The objective of this workshop is to bring
together researchers, students and plant breeders to discuss the
latest advances and their applications in this domain.
Organized at Versailles, by IJPB
(Institut Jean Pierre Bourgin) - INRAE Versailles and EBI (Ecologie
et Biologie des Interactions, CNRS/Université de Poitiers)
Team SEVE (Laboratory CNRS-University, Transport de sucres et réponses
des plantes aux contraintes abiotiques) - University of Poitiers.
This workshop follows up a serie
of events that have been organized by the same co-organizers at
Poitiers (Le phloème dans tous ses états”, 2004,
2012), with the support of the SFBV (Société Française
de Biologie Végétale).
Dinant, Senior Scientist, INRAE, IJPB Versailles
Dr. Rémi Lemoine, Senior Scientist, CNRS, Université
Dr. Nathalie Pourtau, Assistant Professor, Université de
Local Organization Committee:
Philippe Porée, INRAE Versailles
Gisèle Cordillot (SFBV)
and more information
Workshop Sugar Allocation in Plants website
ZELCOR Summer School 2020
Due to the COVID-19 situation, the Zelcor Summer School
is cancelled in July.
We hope to reschedule it later and will keep you informed.
6-10 juillet 2020
by the success of the 1st Zelcor
summer school (Wageningen, 2018), Zelcor consortium offers a second
edition on the topic: “Zero waste biorefineries: value chain
approach, methods and processes for lignin up-grading”.
This international event organized
by INRAE will be held in Versailles (France) from 6th to 10th July.
It targets a mixed public of academic and private partners (total
of 50 participants) with the objective to favor interactions between
scientific research and industry. The programme includes lectures
dedicated to the latest advances in plant cell wall knowledge and
biorefinery technologies (4 ½ days), lab training on analytical
technics or tutorials on sustainability assessment (1 day), visit
of a biorefinery site (1 day), and work in group on study cases
(2 ½ days).
The last day sessions jointly organized
with the Saclay Plant Science summer school will allow all the participants
to benefit from the lectures of two invited speakers involved in
cellulosic ethanol value chains and to share their poster and project
Scientific Committee IJPB :
Philippe Porée, INRAE Versailles
Zimmermann, IJPB, INRAE, Versailles
and more information ZELCOR
Summer School 2020 website