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1. Differential resistance and acclimation of two coral species to chronic nutrient enrichment reflect life‐history traits

   https://doi.org/10.1111/1365-2435.13780  

   Fox, Michael D. ; Nelson, Craig E. ; Oliver, Thomas A. ; Quinlan, Zachary A. ; Remple, Kristina ; Glanz, Jess ; Smith, Jennifer E. ; Putnam, Hollie M. ; Fox, ed., Charles ( March 2021 , Functional Ecology)

   The effects of nutrient pollution on coral reef ecosystems are multifaceted. Numerous experiments have sought to identify the physiological effects of nutrient enrichment on reef‐building corals, but the results have been variable and sensitive to choices of nutrient quantity, chemical composition and exposure duration.

   To test the effects of chronic, ecologically relevant nutrient enrichment on coral growth and photophysiology, we conducted a 5‐week continuous dosing experiment on two Hawaiian coral species,Porites compressaandPocillopora acuta. We acclimated coral fragments to five nutrient concentrations (0.1–7 µMand 0.06–2.24 µM) with constant stoichiometry 2.5:1 nitrate to phosphate) bracketing in situ observations from reefs throughout the Pacific.

   Nutrient enrichment linearly increased photophysiological performance of both species within 3 weeks. The effect of nutrients onP. acutaphotochemical efficiency increased through time while a consistent response inP. compressaindicated acclimation to elevated nutrients within 5 weeks. Endosymbiont densities and total chlorophyll concentrations also increased proportionally with nutrient enrichment inP. acuta, but not inP. compressa, revealing contrasting patterns of host–symbiont acclimatization.

   The two species also exhibited contrasting effects of nutrient enrichment on skeletal growth. Calcification was enhanced at low nutrient enrichment (1 µM) inP. acuta, but comparable to the control at higher concentrations, whereas calcification was reduced inP. compressa(30%–35%) above 3 µM.

   Stable isotope analysis revealed species‐specific nitrogen uptake dynamics in the coral–algal symbiosis. The endosymbionts ofP. acutaexhibited increased nitrogen uptake (decreased δ¹⁵N) and incorporation (19%–31% decrease in C:N ratios) across treatments. In contrast,P. compressaendosymbionts maintained constant δ¹⁵N values and low levels of nitrogen incorporation (9%–11% decrease in C:N ratios). The inability ofP. acutato regulate endosymbiont nutrient uptake may indicate an emerging destabilization in the coral–algal symbiosis under nutrient enrichment that could compromise resistance to additional environmental stressors.

   Our results highlight species‐specific differences in the coral–algal symbiosis, which influence responses to chronic nutrient enrichment. These findings showcase how symbioses can vary among closely related taxa and underscore the importance of considering how life‐history traits modify species response to environmental change.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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2. Yeast of Eden: microbial resistance to glyphosate from a yeast perspective

   https://doi.org/10.1007/s00294-023-01272-4  

   Patriarcheas, Dionysios ; Momtareen, Taizina ; Gallagher, Jennifer E. G. ( June 2023 , Current Genetics)

   First marketed as RoundUp, glyphosate is history’s most popular herbicide because of its low acute toxicity to metazoans and broad-spectrum effectiveness across plant species. The development of glyphosate-resistant crops has led to increased glyphosate use and consequences from the use of glyphosate-based herbicides (GBH). Glyphosate has entered the food supply, spurred glyphosate-resistant weeds, and exposed non-target organisms to glyphosate. Glyphosate targets EPSPS/AroA/Aro1 (orthologs across plants, bacteria, and fungi), the rate-limiting step in the production of aromatic amino acids from the shikimate pathway. Metazoans lacking this pathway are spared from acute toxicity and acquire their aromatic amino acids from their diet. However, glyphosate resistance is increasing in non-target organisms. Mutations and natural genetic variation discovered inSaccharomyces cerevisiaeillustrate similar types of glyphosate resistance mechanisms in fungi, plants, and bacteria, in addition to known resistance mechanisms such as mutations in Aro1 that block glyphosate binding (target-site resistance (TSR)) and mutations in efflux drug transporters non-target-site resistance (NTSR). Recently, genetic variation and mutations in an amino transporter affecting glyphosate resistance have uncovered potential off-target effects of glyphosate in fungi and bacteria. While glyphosate is a glycine analog, it is transported into cells using an aspartic/glutamic acid (D/E) transporter. The size, shape, and charge distribution of glyphosate closely resembles D/E, and, therefore, glyphosate is a D/E amino acid mimic. The mitochondria use D/E in several pathways and mRNA-encoding mitochondrial proteins are differentially expressed during glyphosate exposure. Mutants downstream of Aro1 are not only sensitive to glyphosate but also a broad range of other chemicals that cannot be rescued by exogenous supplementation of aromatic amino acids. Glyphosate also decreases the pH when unbuffered and many studies do not consider the differences in pH that affect toxicity and resistance mechanisms.

    

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3. Global Impacts of Subseasonal (<60 Day) Wind Variability on Ocean Surface Stress, Buoyancy Flux, and Mixed Layer Depth

   https://doi.org/10.1029/2019JC015166  

   Whitt, D. B. ; Nicholson, S. A. ; Carranza, M. M. ( December 2019 , Journal of Geophysical Research: Oceans)

   Subseasonal surface wind variability strongly impacts the annual mean and subseasonal turbulent atmospheric surface fluxes. However, the impacts of subseasonal wind variability on the ocean are not fully understood. Here, we quantify the sensitivity of the ocean surface stress (𝛕), buoyancy flux (B), and mixed layer depth (MLD) to subseasonal wind variability in both a one‐dimensional (1‐D) vertical column model and a three‐dimensional (3‐D) global mesoscale‐resolving ocean/sea ice model. The winds are smoothed by time filtering the pseudo‐stresses, so the mean stress is approximately unchanged, and some important surface flux feedbacks are retained. The 1‐D results quantify the sensitivities to wind variability at different time scales from 120 days to 1 day at a few sites. The 3‐D results quantify the sensitivities to wind variability shorter than 60 days at all locations, and comparisons between 1‐D and 3‐D results highlight the importance of 3‐D ocean dynamics. Globally, subseasonal winds explain virtually all of subseasonal𝛕variance, about half of subseasonalBvariance but only a quarter of subseasonal MLD variance. Subseasonal winds also explain about a fifth of the annual mean MLD and a similar and spatially correlated fraction of the mean friction velocity,whereρ_swis the density of seawater. Hence, the subseasonal MLD variance is relatively insensitive to subseasonal winds despite their strong impact on localBand𝛕variability, but the mean MLD is relatively sensitive to subseasonal winds to the extent that they modify the meanu_*, and both of these sensitivities are modified by 3‐D ocean dynamics.

    

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4. Enhancing hydrogen‐dependent growth of and carbon dioxide fixation by Clostridium ljungdahlii through nitrate supplementation

   https://doi.org/10.1002/bit.26847  

   Emerson, David F. ; Woolston, Benjamin M. ; Liu, Nian ; Donnelly, Mackenzie ; Currie, Devin H. ; Stephanopoulos, Gregory ( December 2018 , Biotechnology and Bioengineering)

   Synthesis gas (syngas) fermentation via the Wood–Ljungdahl pathway is receiving growing attention as a possible platform for the fixation ofand renewable production of fuels and chemicals. However, the pathway operates near the thermodynamic limit of life, resulting in minimal adenosine triphosphate (ATP) production and long doubling times. This calls into question the feasibility of producing high‐energy compounds at industrially relevant levels. In this study, we investigated the possibility of co‐utilizing nitrate as an inexpensive additional electron acceptor to enhance ATP production during‐dependent growth ofClostridium ljungdahlii,Moorella thermoacetica, andAcetobacterium woodii. In contrast to other acetogens tested, growth rate and final biomass titer were improved forC. ljungdahliigrowing on a mixture ofandwhen supplemented with nitrate. Transcriptomic analysis,labeling, and an electron balance were used to understand how electron flux was partitioned betweenand nitrate. We further show that, with nitrate supplementation, the ATP/adenosine diphosphate (ADP) ratio and acetyl‐CoA pools were increased by fivefold and threefold, respectively, suggesting that this strategy could be useful for the production of ATP‐intensive heterologous products from acetyl‐CoA. Finally, we propose a pathway for enhanced ATP production from nitrate and use this as a basis to calculate theoretical yields for a variety of products. This study demonstrates a viable strategy for the decoupling of ATP production from carbon dioxide fixation, which will serve to significantly improve thefixation rate and the production metrics of other chemicals fromandin this host.

    

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5. PROTAC for agriculture: learning from human medicine to generate new biotechnological weed control solutions

   https://doi.org/10.1002/ps.7741  

   Leon, Ramon G. ; Bassham, Diane C. ( September 2023 , Pest Management Science)

   Weed control has relied on the use of organic and inorganic molecules that interfere with druggable targets, especially enzymes, for almost a century. This approach, although effective, has resulted in multiple cases of herbicide resistance. Furthermore, the rate of discovery of new druggable targets that are selective and with favorable environmental profiles has slowed down, highlighting the need for innovative control tools. The arrival of the biotechnology and genomics era gave hope to many that all sorts of new control tools would be developed. However, the reality is that most efforts have been limited to the development of transgenic crops with resistance to a few existing herbicides, which in fact is just another form of selectivity. Proteolysis‐targeting chimera (PROTAC) is a new technology developed to treat human diseases but that has potential for multiple applications in agriculture. This technology uses a small bait molecule linked to an E3 ligand. The 3‐dimensional structure of the bait favors physical interaction with a binding site in the target protein in a manner that allows E3 recruitment, ubiquitination and then proteasome‐mediated degradation. This system makes it possible to circumvent the need to find druggable targets because it can degrade structural proteins, transporters, transcription factors, and enzymes without the need to interact with the active site. PROTAC can help control herbicide‐resistant weeds as well as expand the number of biochemical targets that can be used for weed control. In the present article, we provide an overview of how PROTAC works and describe the possible applications for weed control as well as the challenges that this technology might face during development and implementation for field uses. © 2023 The Authors.Pest Management Sciencepublished by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

    

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