Biology subjects

Walker, B. E.

Publications and source records attributed to Walker, B. E..

3 recordsLinked to original sources

bioRxiv2025

Big angiosperm genera are priorities for conservation

Species in big angiosperm genera ([≥]500 species) are often considered to be less well-known than those in smaller genera. Consequently, species in big genera are likely underrepresented in conservation at all levels, from analyses to actions. However, emerging evidence indicates that species in larger genera tend to have smaller geographic ranges (a strong correlate of increased extinction risk). Here, we test the generality of this pattern by quantifying the relationships between plant taxon size, extinction risk and climatic zone on a global scale. We find that species in larger genera are more likely to have small ranges, less likely to have a global Red List assessment, and, when assessed, are more likely to be threatened. Persistent obstacles to improving conservation documentation of big genera include taxonomic uncertainty, data shortfalls and number of species involved, requiring continued collaboration between taxonomy and conservation to reduce this bias and enable effective conservation of the quarter of plant species that big genera encompass. Article Impact StatementSpecies in big angiosperm genera are under-studied, under-assessed, and their extinction risk has been underestimated.

ecology↗

bioRxiv2025

300 billion years of angiosperm evolution at risk of extinction

Extinction results in not only loss of species, but also loss of the unique evolutionary history that they represent and the irreplaceable features they exhibit. There is broad consensus regarding the necessity to optimise the preservation of the tree of life by including evolutionary information in conservation prioritisation, a notion also endorsed by major policy frameworks1-4. However, evolutionarily-informed prioritisations are lacking for most plants, resulting in a taxonomic imbalance in the evolutionary information incorporated in global biodiversity analyses, which has undermined conservation for decades. Here, we use comprehensive species-level phylogenetic trees, and extinction risk estimates, to generate the first global assessment of angiosperm evolutionary history at risk, and to identify phylogenetically-informed conservation priorities for the worlds flowering plants. We estimate that more than one fifth of angiosperm evolutionary history is at risk of extinction in the short term. Using the Evolutionarily Distinct and Globally Endangered5,6 approach, we identify 9,945 threatened plant species that disproportionately account for total evolutionary history at risk. Species and area prioritisations incorporating evolutionary history are urgently needed to correct imbalances between plants and animals, monitor the effectiveness of conservation efforts, and optimise conservation resource allocation in the face of increasing human pressures on Earths biodiversity.

evolutionary biology↗

bioRxiv2018

Regulation of FtsZ levels in Escherichia coli in slow growth conditions

A key regulator of cell division in most walled bacteria is the FtsZ protein that assembles into protofilaments attached to the membrane at midcell. These dynamic protofilament assemblies, known as the Z-ring, act as a scaffold for more than two dozen proteins involved in synthesis of septal cell envelopes. What triggers the formation of the Z-ring during the cell cycle is poorly understood. In Escherichia coli model organism, the common view is that FtsZ concentration is constant throughout its doubling time and therefore regulation of assembly should be controlled by some yet to be identified protein-protein interactions. Here we show using quantitative analysis of newly developed fluorescent reporter that FtsZ concentration varies in a cell-cycle dependent manner in slow growth conditions and that upregulation of FtsZ synthesis correlates with the formation of the Z-ring. About 4-fold upregulation of FtsZ synthesis in the first half of the cell cycle is followed by its rapid degradation by ClpXP protease in the last 10% of the cell cycle. The initiation of rapid degradation coincides with dissociation of FtsZ from the septum. Altogether, our data indicate that the Z-ring formation in slow growth conditions in E. coli is controlled by a regulatory sequence where upregulation of an essential cell cycle factor is followed by its degradation.\n\nSignificanceFtsZ is the key regulator for bacterial cell division. It initiates division by forming a dynamic ring-like structure, the Z-ring, at the mid-cell. Here we show that, contrarily to the current paradigm, FtsZ concentration in Escherichia coli model organism varies throughout cell cycle in slow growth conditions. Faster FtsZ synthesis in the first half of the cell cycle is followed by its rapid degradation by ClpXP protease in the end of the cell cycle. Upregulation of FtsZ synthesis correlates with the formation of the Z-ring. Our data demonstrates that in slow growth E. coli cell division progresses according to paradigm where upregulation of essential cell cycle factor is followed by its degradation.

cell biology↗