Leaf carbon export and non-structural carbohydrates in relation to diurnal water dynamics in mature oak trees
Trees typically experience large diurnal depressions in water potential, which may impede carbon export from leaves during the day because the xylem is the source of water for the phloem. As water potential becomes more negative, higher phloem osmotic concentrations are needed to draw water in from the xylem. Generating this high concentration of sugar in the phloem is particularly an issue for the ~50% of trees that exhibit passive loading. These ideas motivate the hypothesis that carbon export in woody plants occurs predominantly at night, with sugars that accumulate during the day assisting in mesophyll turgor maintenance or being converted to starch. To test this, diurnal and seasonal patterns of leaf non-structural carbohydrates, photosynthesis, solute, and water potentials were measured, and carbon export was estimated in leaves of five mature (> 20 m tall) red oak (Quercus rubra) trees, a species characterized as a passive loader.
A standard protocol for reporting species distribution models
Zurell et al. propose a standard protocol for reporting Species distribution models (SDMs), with an emphasis on describing how a study's objective is achieved through a series of modeling decisions. We call this the ODMAP (Overview, Data, Model, Assessment and Prediction) protocol, as its components reflect the main steps involved in building SDMs and other empirically‐based biodiversity models. The ODMAP protocol serves two main purposes. First, it provides a checklist for authors, detailing key steps for model building and analyses, and thus represents a quick guide and generic workflow for modern SDMs. Second, it introduces a structured format for documenting and communicating the models, ensuring transparency and reproducibility, facilitating peer review and expert evaluation of model quality, as well as meta‐analyses.
A single gene underlies the dynamic evolution of poplar sex determination
show that diverse poplar species carry partial duplicates of the ARABIDOPSIS RESPONSE REGULATOR 17 (ARR17) orthologue in the male-specific region of the Y chromosome. These duplicates give rise to small RNAs apparently causing male-specific DNA methylation and silencing of the ARR17 gene. CRISPR–Cas9-induced mutations demonstrate that ARR17 functions as a sex switch, triggering female development when on and male development when off.
Ecological Differentiation and Incipient Speciation in the Fungal Pathogen Causing Rice Blast
Natural variation in plant pathogens has an impact on food security and ecosystem health. The rice blast fungus Pyricularia oryzae, which limits rice production in all rice-growing areas, is structured into multiple lineages. Diversification and the maintenance of multiple rice blast lineages have been proposed to be due to separation in different areas and differential adaptation to rice subspecies. However, the precise world distribution of rice blast populations, and the factors controlling their presence and maintenance in the same geographic areas, remain largely unknown. Thierry et al. used genotyping data for 886 isolates from more than 185 locations in 51 countries to show that P. oryzae is structured into one recombining and three clonal lineages, each with broad geographic distributions.
Unexpected conservation and global transmission of agrobacterial virulence plasmids
Plasmids are widespread among bacteria and are important because they spread virulence and antibiotic resistance traits, among others. They are horizontally transferred between strains and species, so it is difficult to work out their evolution and epidemiology. Agrobacteria, a diverse grouping of species that infect plants, inject oncogenic Ti and Ri plasmids, which cause crown galls and hairy root diseases, respectively. The upside is that these plasmids have become valuable biotechnological tools. Weisberg et al. combed through an 80-year-old collection of Agrobacterium strains but found a surprisingly low diversity of plasmids.
Global variation in the thermal tolerances of plants
Knowledge of how thermal tolerances are distributed across major clades and biogeographic regions is important for understanding biome formation and climate change responses. However, most research has concentrated on animals, and we lack equivalent knowledge for other organisms. Lancaster and Humphreys compile global data on heat and cold tolerances of plants, showing that many, but not all, broad-scale patterns known from animals are also true for plants.
Academic leaders must support inclusive scientific communities during COVID-19
The COVID-19 pandemic poses major challenges for all sectors of society, including scientists faced with abrupt disruptions and redirections of research and higher education. The consequences of this crisis will disproportionately impact early-career scientists; especially those from communities historically underrepresented, disadvantaged and/or discriminated in the fields of environmental sciences, including women, researchers from the Global South and persons with disabilities. Maas et al. call for a collective effort by the entire scientific community, especially those in leadership positions, to respond to the short- and long-term challenges of this crisis and to protect decades of efforts to build an inclusive scientific community.
Nature Ecology & Evolution
Brassinosteroids Inhibit Autotropic Root Straightening by Modifying Filamentous-Actin Organization and Dynamics | Plant Science
When positioned horizontally, roots grow down toward the direction of gravity. This phenomenon, called gravitropism, is influenced by most of the major plant hormones including brassinosteroids. Epi-brassinolide (eBL) was previously shown to enhance root gravitropism, a phenomenon similar to the response of roots exposed to the actin inhibitor, latrunculin B (LatB). This led de Bang et al. to hypothesize that eBL might enhance root gravitropism through its effects on filamentous-actin (F-actin). This hypothesis was tested by comparing gravitropic responses of maize (Zea mays) roots treated with eBL or LatB. LatB- and eBL-treated roots displayed similar enhanced downward growth compared with controls when vertical roots were oriented horizontally.
Frontiers in Plant Science
Metabolic Cellular Communications: Feedback Mechanisms between Membrane Lipid Homeostasis and Plant Development
Boutté and Jaillais review several recent examples of lipid metabolic changes highlighting the intricate feedbacks between membrane lipid homeostasis and plant development. In particular, these examples illustrate how all aspects of membrane lipid metabolic pathways are targeted by these feedback regulations. We propose that the time has come to consider membrane lipids and lipid metabolism as an integral part of the developmental program needed to build a plant.
Highly active rubiscos discovered by systematic interrogation of natural sequence diversity
CO2 is converted into biomass almost solely by the enzyme rubisco. The poor carboxylation properties of plant rubiscos have led to efforts that made it the most kinetically characterized enzyme, yet these studies focused on < 5% of its natural diversity. Davidi et al. searched for fast‐carboxylating variants by systematically mining genomic and metagenomic data. Approximately 33,000 unique rubisco sequences were identified and clustered into ≈ 1,000 similarity groups.
The EMBO Journal