Balancing trade-offs: Enhanced carbon assimilation and productivity with reduced nutritional value in a well-watered C pasture under a warmer CO-enriched atmosphere.

The concentration of atmospheric CO and temperature are pivotal components of ecosystem productivity, carbon balance, and food security. In this study, we investigated the impacts of a warmer climate (+2 °C above ambient temperature) and an atmosphere enriched with CO (600 ppm) on gas exchange, antioxidant enzymatic system, growth, nutritive value, and digestibility of a well-watered, managed pasture of Megathyrsus maximus, a tropical C forage grass, under field conditions. Elevated [CO] (eC) improved photosynthesis and reduced stomatal conductance, resulting in increased water use efficiency and plant C content.

Lateral gene transfer generates accessory genes that accumulate at different rates within a grass lineage.

Lateral gene transfer (LGT) is the movement of DNA between organisms without sexual reproduction. The acquired genes represent genetic novelties that have independently evolved in the donor's genome. Phylogenetic methods have shown that LGT is widespread across the entire grass family, although we know little about the underlying dynamics.

Alloteropsis semialata as a study system for C4 evolution in grasses.

Background: Numerous groups of plants have adapted to CO2 limitations by independently evolving C4 photosynthesis. This trait relies on concerted changes in anatomy and biochemistry to concentrate CO2 within the leaf and thereby boost productivity in tropical conditions. The ecological and economic importance of C4 photosynthesis has motivated intense research, often relying on comparisons between distantly related C4 and non-C4 plants.

Leaf anatomy explains the strength of C activity within the grass species Alloteropsis semialata.

C photosynthesis results from anatomical and biochemical characteristics that together concentrate CO around ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), increasing productivity in warm conditions. This complex trait evolved through the gradual accumulation of components, and particular species possess only some of these, resulting in weak C activity. The consequences of adding C components have been modelled and investigated through comparative approaches, but the intraspecific dynamics responsible for strengthening the C pathway remain largely unexplored.

Upregulation of C characteristics does not consistently improve photosynthetic performance in intraspecific hybrids of a grass.

C photosynthesis is thought to have evolved via intermediate stages, with changes towards the C phenotype gradually enhancing photosynthetic performance. This hypothesis is widely supported by modelling studies, but experimental tests are missing. Mixing of C components to generate artificial intermediates can be achieved via crossing, and the grass Alloteropsis semialata represents an outstanding study system since it includes C and non-C populations.

Hybridization boosts dispersal of two contrasted ecotypes in a grass species.

Genetic exchanges between closely related groups of organisms with different adaptations have well-documented beneficial and detrimental consequences. In plants, pollen-mediated exchanges affect the sorting of alleles across physical landscapes and influence rates of hybridization. How these dynamics affect the emergence and spread of novel phenotypes remains only partially understood.

Low dispersal and ploidy differences in a grass maintain photosynthetic diversity despite gene flow and habitat overlap.

Geographical isolation facilitates the emergence of distinct phenotypes within a single species, but reproductive barriers or selection are needed to maintain the polymorphism after secondary contact. Here, we explore the processes that maintain intraspecific variation of C photosynthesis, a complex trait that results from the combined action of multiple genes. The grass Alloteropsis semialata includes C and non-C populations, which have coexisted as a polyploid series for more than 1 million years in the miombo woodlands of Africa.

Contrasted histories of organelle and nuclear genomes underlying physiological diversification in a grass species.

C photosynthesis evolved multiple times independently in angiosperms, but most origins are relatively old so that the early events linked to photosynthetic diversification are blurred. The grass is an exception, as this species encompasses C and non-C populations. Using phylogenomics and population genomics, we infer the history of dispersal and secondary gene flow before, during and after photosynthetic divergence in .

Continued Adaptation of C4 Photosynthesis After an Initial Burst of Changes in the Andropogoneae Grasses.

C$_{4}$ photosynthesis is a complex trait that sustains fast growth and high productivity in tropical and subtropical conditions and evolved repeatedly in flowering plants. One of the major C$_{4}$ lineages is Andropogoneae, a group of $\sim $1200 grass species that includes some of the world's most important crops and species dominating tropical and some temperate grasslands. Previous efforts to understand C$_{4}$ evolution in the group have compared a few model C$_{4}$ plants to distantly related C$_{3}$ species so that changes directly responsible for the transition to C$_{4}$ could not be distinguished from those that preceded or followed it.

C anatomy can evolve via a single developmental change.

C photosynthesis is a complex trait that boosts productivity in warm environments. Paradoxically, it evolved independently in numerous plant lineages, despite requiring specialised leaf anatomy. The anatomical modifications underlying C evolution have previously been evaluated through interspecific comparisons, which capture numerous changes besides those needed for C functionality.

Massive over-representation of solute-binding proteins (SBPs) from the tripartite tricarboxylate transporter (TTT) family in the genome of the α-proteobacterium Rhodoplanes sp. Z2-YC6860.

Lineage-specific expansion (LSE) of protein families is a widespread phenomenon in many eukaryotic genomes, but is generally more limited in bacterial genomes. Here, we report the presence of 434 genes encoding solute-binding proteins (SBPs) from the tripartite tricarboxylate transporter (TTT) family, within the 8.2 Mb genome of the α-proteobacterium Rhodoplanes sp.

Tripartite ATP-Independent Periplasmic (TRAP) Transporters and Tripartite Tricarboxylate Transporters (TTT): From Uptake to Pathogenicity.

The ability to efficiently scavenge nutrients in the host is essential for the viability of any pathogen. All catabolic pathways must begin with the transport of substrate from the environment through the cytoplasmic membrane, a role executed by membrane transporters. Although several classes of cytoplasmic membrane transporters are described, high-affinity uptake of substrates occurs through Solute Binding-Protein (SBP) dependent systems.

Gene duplication and dosage effects during the early emergence of C4 photosynthesis in the grass genus Alloteropsis.

The importance of gene duplication for evolutionary diversification has been mainly discussed in terms of genetic redundancy allowing neofunctionalization. In the case of C4 photosynthesis, which evolved via the co-option of multiple enzymes to boost carbon fixation in tropical conditions, the importance of genetic redundancy has not been consistently supported by genomic studies. Here, we test for a different role for gene duplication in the early evolution of C4 photosynthesis, via dosage effects creating rapid step changes in expression levels.