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"Nicolas Martin"
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Living material assembly of bacteriogenic protocells
Advancing the spontaneous bottom-up construction of artificial cells with high organizational complexity and diverse functionality remains an unresolved issue at the interface between living and non-living matter
1
,
2
,
3
–
4
. Here, to address this challenge, we developed a living material assembly process based on the capture and on-site processing of spatially segregated bacterial colonies within individual coacervate microdroplets for the endogenous construction of membrane-bounded, molecularly crowded, and compositionally, structurally and morphologically complex synthetic cells. The bacteriogenic protocells inherit diverse biological components, exhibit multifunctional cytomimetic properties and can be endogenously remodelled to include a spatially partitioned DNA–histone nucleus-like condensate, membranized water vacuoles and a three-dimensional network of F-actin proto-cytoskeletal filaments. The ensemble is biochemically energized by ATP production derived from implanted live
Escherichia coli
cells to produce a cellular bionic system with amoeba-like external morphology and integrated life-like properties. Our results demonstrate a bacteriogenic strategy for the bottom-up construction of functional protoliving microdevices and provide opportunities for the fabrication of new synthetic cell modules and augmented living/synthetic cell constructs with potential applications in engineered synthetic biology and biotechnology.
A bacteriogenic strategy for constructing membrane-bounded, molecularly crowded, and compositionally, structurally and morphologically complex synthetic cells provides opportunities for the fabrication of new synthetic cell modules and augmented living/synthetic cell constructs.
Journal Article
Growth duration is a better predictor of stem increment than carbon supply in a Mediterranean oak forest: implications for assessing forest productivity under climate change
Understanding whether tree growth is limited by carbon gain (source limitation) or by the direct effect of environmental factors such as water deficit or temperature (sink limitation) is crucial for improving projections of the effects of climate change on forest productivity.
We studied the relationships between tree basal area (BA) variations, eddy covariance carbon fluxes, predawn water potential (Ψpd) and temperature at different timescales using an 8-yr dataset and a rainfall exclusion experiment in a Quercus ilex Mediterranean coppice.
At the daily timescale, during periods of low temperature (< 5°C) and high water deficit (< −1.1 MPa), gross primary productivity and net ecosystem productivity remained positive whereas the stem increment was nil. Thus, stem increment appeared limited by drought and temperature rather than by carbon input. Annual growth was accurately predicted by the duration of BA increment during spring (Δt
t0–t1). The onset of growth (t
0) was related to winter temperatures and the summer interruption of growth (t
1) to a threshold Ψpd value of −1.1 MPa.
We suggest that using environmental drivers (i.e. drought and temperature) to predict stem growth phenology can contribute to an improvement in vegetation models and may change the current projections of Mediterranean forest productivity under climate change scenarios.
Journal Article
On the minimum leaf conductance: its role in models of plant water use, and ecological and environmental controls
Summary When the rate of photosynthesis is greatly diminished, such as during severe drought, extreme temperature or low light, it seems advantageous for plants to close stomata and completely halt water loss. However, water loss continues through the cuticle and incompletely closed stomata, together constituting the leaf minimum conductance (gmin). In this review, we critically evaluate the sources of variation in gmin, quantitatively compare various methods for its estimation, and illustrate the role of gmin in models of leaf gas exchange. A literature compilation of gmin as measured by the weight loss of detached leaves is presented, which shows much variation in this trait, which is not clearly related to species groups, climate of origin or leaf type. Much evidence points to the idea that gmin is highly responsive to the growing conditions of the plant, including soil water availability, temperature and air humidity – as we further demonstrate with two case studies. We pay special attention to the role of the minimum conductance in the Ball–Berry model of stomatal conductance, and caution against the usual regression-based method for its estimation. The synthesis presented here provides guidelines for the use of gmin in ecosystem models, and points to clear research gaps for this drought tolerance trait.
Journal Article
Non-enzymatic oligonucleotide ligation in coacervate protocells sustains compartment-content coupling
Modern cells are complex chemical compartments tightly regulated by an underlying DNA-encoded program. Achieving a form of coupling between molecular content, chemical reactions, and chassis in synthetic compartments represents a key step to the assembly of evolvable protocells but remains challenging. Here, we design coacervate droplets that promote non-enzymatic oligonucleotide polymerization and that restructure as a result of the reaction dynamics. More specifically, we rationally exploit complexation between end-reactive oligonucleotides able to stack into long physical polymers and a cationic azobenzene photoswitch to produce three different phases—soft solids, liquid crystalline or isotropic coacervates droplets—each of them having a different impact on the reaction efficiency. Dynamical modulation of coacervate assembly and dissolution via
trans
-
cis
azobenzene photo-isomerization is used to demonstrate cycles of light-actuated oligonucleotide ligation. Remarkably, changes in the population of polynucleotides during polymerization induce phase transitions due to length-based DNA self-sorting to produce multiphase coacervates. Overall, by combining a tight reaction-structure coupling and environmental responsiveness, our reactive coacervates provide a general route to the non-enzymatic synthesis of polynucleotides and pave the way to the emergence of a primitive compartment-content coupling in membrane-free protocells.
Achieving a form of coupling between molecular content, chemical reactions, and chassis in synthetic compartments represents a key step to the assembly of evolvable protocells but remains challenging. Here, the authors design coacervate droplets that promote non-enzymatic oligonucleotide polymerization and that restructure as a result of the reaction dynamics.
Journal Article
Coordination of stem and leaf traits define different strategies to regulate water loss and tolerance ranges to aridity
Adaptation to drought involves complex interactions of traits that vary within and among species. To date, few data are available to quantify within-species variation in functional traits and they are rarely integrated into mechanistic models to improve predictions of species response to climate change.We quantified intraspecific variation in functional traits of two Hakea species growing along an aridity gradient in southeastern Australia. Measured traits were later used to parameterise the model SurEau to simulate a transplantation experiment to identify the limits of drought tolerance.Embolism resistance varied between species but not across populations. Instead, populations adjusted to drier conditions via contrasting sets of trait trade-offs that facilitated homeostasis of plant water status. The species from relatively mesic climate, Hakea dactyloides, relied on tight stomatal control whereas the species from xeric climate, Hakea leucoptera dramatically increased Huber value and leaf mass per area, while leaf area index (LAI) and epidermal conductance (g(min)) decreased. With trait variability, SurEau predicts the plasticity of LAI and g(min) buffers the impact of increasing aridity on population persistence.Knowledge of within-species variability in multiple drought tolerance traits will be crucial to accurately predict species distributional limits.
Journal Article
A vast, thin plane of corotating dwarf galaxies orbiting the Andromeda galaxy
About half of the satellites in the Andromeda galaxy (M 31), all with the same sense of rotation about their host, form a planar subgroup that is extremely wide but also very thin.
The Andromeda galaxy's orbiting companions
Giant spiral galaxies are assembled from smaller systems through a process known as hierarchical clustering. In orbit around these giants are dwarf galaxies, which are presumably remnants of the galactic progenitors. Recent studies of the dwarf galaxies of the Milky Way have led some astronomers to suspect that their orbits are not randomly distributed. This suspicion, which challenges current theories of galaxy formation, is now bolstered by the discovery of a plane of dwarf galaxies corotating as a coherent pancake-like structure around the Andromeda galaxy, the Milky Way's close neighbour and in many respects its 'twin'. The structure is extremely thin yet contains about half of the dwarf galaxies in the Andromeda system. The authors report that 13 of the 15 satellites in the plane share the same sense of rotation.
Dwarf satellite galaxies are thought to be the remnants of the population of primordial structures that coalesced to form giant galaxies like the Milky Way
1
. It has previously been suspected
2
that dwarf galaxies may not be isotropically distributed around our Galaxy, because several are correlated with streams of H
i
emission, and may form coplanar groups
3
. These suspicions are supported by recent analyses
4
,
5
,
6
,
7
. It has been claimed
7
that the apparently planar distribution of satellites is not predicted within standard cosmology
8
, and cannot simply represent a memory of past coherent accretion. However, other studies dispute this conclusion
9
,
10
,
11
. Here we report the existence of a planar subgroup of satellites in the Andromeda galaxy (M 31), comprising about half of the population. The structure is at least 400 kiloparsecs in diameter, but also extremely thin, with a perpendicular scatter of less than 14.1 kiloparsecs. Radial velocity measurements
12
,
13
,
14
,
15
reveal that the satellites in this structure have the same sense of rotation about their host. This shows conclusively that substantial numbers of dwarf satellite galaxies share the same dynamical orbital properties and direction of angular momentum. Intriguingly, the plane we identify is approximately aligned with the pole of the Milky Way’s disk and with the vector between the Milky Way and Andromeda.
Journal Article
A stellar stream remnant of a globular cluster below the metallicity floor
Stellar ejecta gradually enrich the gas out of which subsequent stars form, making the least chemically enriched stellar systems direct fossils of structures formed in the early Universe
1
. Although a few hundred stars with metal content below 1,000th of the solar iron content are known in the Galaxy
2
–
4
, none of them inhabit globular clusters, some of the oldest known stellar structures. These show metal content of at least approximately 0.2% of the solar metallicity
(
[
Fe
/
H
]
≳
−
2.7
)
. This metallicity floor appears universal
5
,
6
, and it has been proposed that protogalaxies that merged into the galaxies we observe today were simply not massive enough to form clusters that survived to the present day
7
. Here we report observations of a stellar stream, C-19, whose metallicity is less than 0.05% of the solar metallicity
(
[
F
e
/
H
]
=
−
3.38
±
0.06
(
s
t
a
t
i
s
t
i
c
a
l
)
±
0.20
(
s
y
s
t
e
m
a
t
i
c
)
)
. The low metallicity dispersion and the chemical abundances of the C-19 stars show that this stream is the tidal remnant of the most metal-poor globular cluster ever discovered, and is significantly below the purported metallicity floor: clusters with significantly lower metallicities than observed today existed in the past and contributed their stars to the Milky Way halo.
Observations of a stellar stream below the metallicity floor for a disrupted globular cluster are described.
Journal Article
Using agro-ecological zones to improve the representation of a multi-environment trial of soybean varieties
This research introduces a novel framework for enhancing soybean cultivation in North America by categorizing growing environments into distinct ecological and maturity-based zones. Using an integrated analysis of long-term climatic data and records of soybean varietal trials, this research generates a zonal environmental characterization which captures major components of the growing environment which affect the range of adaptation of soybean varieties. These findings have immediate applications for optimizing multi-environment soybean trials. This characterization allows breeders to assess the environmental representation of a multi-environmental trial of soybean varieties, and to strategize the distribution of testing and the placement of test sites accordingly. This application is demonstrated with a historical scenario of a soybean multi-environment trial, using two resource allocation models: one targeted towards improving the general adaptation of soybean varieties, which focuses on widely cultivated areas, and one targeted towards specific adaptation, which captures diverse environmental conditions. Ultimately, the study aims to improve the efficiency and impact of soybean breeding programs, leading to the development of cultivars resilient to variable and changing climates.
Journal Article