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1. IsoSeq transcriptome assembly of C ₃ panicoid grasses provides tools to study evolutionary change in the Panicoideae

   https://doi.org/10.1002/pld3.203  

   Carvalho, Daniel S.; Nishimwe, Aime V.; Schnable, James C. (February 2020, Plant Direct)

   Abstract The number of plant species with genomic and transcriptomic data has been increasing rapidly. The grasses—Poaceae—have been well represented among species with published reference genomes. However, as a result the genomes of wild grasses are less frequently targeted by sequencing efforts. Sequence data from wild relatives of crop species in the grasses can aid the study of domestication, gene discovery for breeding and crop improvement, and improve our understanding of the evolution of C₄photosynthesis. Here, we used long‐read sequencing technology to characterize the transcriptomes of three C₃panicoid grass species:Dichanthelium oligosanthes,Chasmanthium laxum, andHymenachne amplexicaulis. Based on alignments to the sorghum genome, we estimate that assembled consensus transcripts from each species capture between 54.2% and 65.7% of the conserved syntenic gene space in grasses. Genes co‐opted into C₄were also well represented in this dataset, despite concerns that because these genes might play roles unrelated to photosynthesis in the target species, they would be expressed at low levels and missed by transcript‐based sequencing. A combined analysis using syntenic orthologous genes from grasses with published reference genomes and consensus long‐read sequences from these wild species was consistent with previously published phylogenies. It is hoped that these data, targeting underrepresented classes of species within the PACMAD grasses—wild species and species utilizing C₃photosynthesis—will aid in future studies of domestication and C₄evolution by decreasing the evolutionary distance between C₄and C₃species within this clade, enabling more accurate comparisons associated with evolution of the C₄pathway. 

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2. The competitive advantage of a constitutive CAM species over a C ₄ grass species under drought and CO ₂ enrichment

   https://doi.org/10.1002/ecs2.2721  

   Yu, Kailiang; D'Odorico, Paolo; Collins, Scott L.; Carr, David; Porporato, Amilcare; Anderegg, William R. L.; Gilhooly, III, William P.; Wang, Lixin; Bhattachan, Abinash; Bartlett, Mark; et al (May 2019, Ecosphere)

   Abstract Plants with crassulacean acid metabolism (CAM) are increasing in distribution and abundance in drylands worldwide, but the underlying drivers remain unknown. We investigate the impacts of extreme drought and CO₂enrichment on the competitive relationships between seedlings ofCylindropuntia imbricata(CAM species) andBouteloua eriopoda(C₄grass), which coexist in semiarid ecosystems across the Southwestern United States. Our experiments under altered water and CO₂water conditions show thatC. imbricatapositively responded to CO₂enrichment under extreme drought conditions, whileB. eriopodadeclined from drought stress and did not recover after the drought ended. Conversely, in well‐watered conditionsB. eriopodahad a strong competitive advantage onC. imbricatasuch that the photosynthetic rate and biomass (per individual) ofC. imbricatagrown withB. eriopodawere lower relative to when growing alone. A meta‐analysis examining multiple plant families across global drylands shows a positive response of CAM photosynthesis and productivity to CO₂enrichment. Collectively, our results suggest that under drought and elevated CO₂concentrations, projected with climate change, the competitive advantage of plant functional groups may shift and the dominance of CAM plants may increase in semiarid ecosystems. 

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3. Nanotechnology Approaches for Chloroplast Biotechnology Advancements

   https://doi.org/10.3389/fpls.2021.691295  

   Newkirk, Gregory M.; de Allende, Pedro; Jinkerson, Robert E.; Giraldo, Juan Pablo (July 2021, Frontiers in Plant Science)

   Photosynthetic organisms are sources of sustainable foods, renewable biofuels, novel biopharmaceuticals, and next-generation biomaterials essential for modern society. Efforts to improve the yield, variety, and sustainability of products dependent on chloroplasts are limited by the need for biotechnological approaches for high-throughput chloroplast transformation, monitoring chloroplast function, and engineering photosynthesis across diverse plant species. The use of nanotechnology has emerged as a novel approach to overcome some of these limitations. Nanotechnology is enabling advances in the targeted delivery of chemicals and genetic elements to chloroplasts, nanosensors for chloroplast biomolecules, and nanotherapeutics for enhancing chloroplast performance. Nanotechnology-mediated delivery of DNA to the chloroplast has the potential to revolutionize chloroplast synthetic biology by allowing transgenes, or even synthesized DNA libraries, to be delivered to a variety of photosynthetic species. Crop yield improvements could be enabled by nanomaterials that enhance photosynthesis, increase tolerance to stresses, and act as nanosensors for biomolecules associated with chloroplast function. Engineering isolated chloroplasts through nanotechnology and synthetic biology approaches are leading to a new generation of plant-based biomaterials able to self-repair using abundant CO 2 and water sources and are powered by renewable sunlight energy. Current knowledge gaps of nanotechnology-enabled approaches for chloroplast biotechnology include precise mechanisms for entry into plant cells and organelles, limited understanding about nanoparticle-based chloroplast transformations, and the translation of lab-based nanotechnology tools to the agricultural field with crop plants. Future research in chloroplast biotechnology mediated by the merging of synthetic biology and nanotechnology approaches can yield tools for precise control and monitoring of chloroplast function in vivo and ex vivo across diverse plant species, allowing increased plant productivity and turning plants into widely available sustainable technologies. 

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4. C₄ photosynthesis, trait spectra, and the fast‐efficient phenotype

   https://doi.org/10.1111/nph.70057  

   Monson, Russell K; Li, Shuai; Ainsworth, Elizabeth A; Fan, Yuzhen; Hodge, John G; Knapp, Alan K; Leakey, Andrew_D B; Lombardozzi, Danica; Reed, Sasha C; Sage, Rowan F; et al (May 2025, New Phytologist)

   Summary It has been 60 years since the discovery of C₄photosynthesis, an event that rewrote our understanding of plant adaptation, ecosystem responses to global change, and global food security. Despite six decades of research, one aspect of C₄photosynthesis that remains poorly understood is how the pathway fits into the broader context of adaptive trait spectra, which form our modern view of functional trait ecology. The C₄CO₂‐concentrating mechanism supports a general C₄plant phenotype capable of fast growth and high resource‐use efficiencies. The fast‐efficient C₄phenotype has the potential to operate at high productivity rates, while allowing for less biomass allocation to root production and nutrient acquisition, thereby providing opportunities for the evolution of novel trait covariances and the exploitation of new ecological niches. We propose the placement of the C₄fast‐efficient phenotype near the acquisitive pole of the world‐wide leaf economic spectrum, but with a pathway‐specific span of trait space, wherein selection shapes both acquisitive and conservative adaptive strategies. A trait‐based perspective of C₄photosynthesis will open new paths to crop improvement, global biogeochemical modeling, the management of invasive species, and the restoration of disturbed ecosystems, particularly in grasslands. 

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5. Mapping the global distribution of C4 vegetation using observations and optimality theory

   https://doi.org/10.1038/s41467-024-45606-3  

   Luo, Xiangzhong; Zhou, Haoran; Satriawan, Tin W.; Tian, Jiaqi; Zhao, Ruiying; Keenan, Trevor F.; Griffith, Daniel M.; Sitch, Stephen; Smith, Nicholas G.; Still, Christopher J. (February 2024, Nature Communications)

   Abstract Plants with the C₄photosynthesis pathway typically respond to climate change differently from more common C₃-type plants, due to their distinct anatomical and biochemical characteristics. These different responses are expected to drive changes in global C₄and C₃vegetation distributions. However, current C₄vegetation distribution models may not predict this response as they do not capture multiple interacting factors and often lack observational constraints. Here, we used global observations of plant photosynthetic pathways, satellite remote sensing, and photosynthetic optimality theory to produce an observation-constrained global map of C₄vegetation. We find that global C₄vegetation coverage decreased from 17.7% to 17.1% of the land surface during 2001 to 2019. This was the net result of a reduction in C₄natural grass cover due to elevated CO₂favoring C₃-type photosynthesis, and an increase in C₄crop cover, mainly from corn (maize) expansion. Using an emergent constraint approach, we estimated that C₄vegetation contributed 19.5% of global photosynthetic carbon assimilation, a value within the range of previous estimates (18–23%) but higher than the ensemble mean of dynamic global vegetation models (14 ± 13%; mean ± one standard deviation). Our study sheds insight on the critical and underappreciated role of C₄plants in the contemporary global carbon cycle. 

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