Monitoring nutrients in plants with genetically encoded sensors: achievements and perspectives.

Understanding mechanisms of nutrient allocation in organisms requires precise knowledge of the spatiotemporal dynamics of small molecules in vivo. Genetically encoded sensors are powerful tools for studying nutrient distribution and dynamics, as they enable minimally invasive monitoring of nutrient steady-state levels in situ. Numerous types of genetically encoded sensors for nutrients have been designed and applied in mammalian cells and fungi. However, to date, their application for visualizing changing nutrient levels in planta remains limited. Systematic sensor-based approaches could provide the quantitative, kinetic information on tissue-specific, cellular, and subcellular distributions and dynamics of nutrients in situ that is needed for the development of theoretical nutrient flux models that form the basis for future crop engineering. Here, we review various approaches that can be used to measure nutrients in planta with an overview over conventional techniques, as well as genetically encoded sensors currently available for nutrient monitoring, and discuss their strengths and limitations. We provide a list of currently available sensors and summarize approaches for their application at the level of cellular compartments and organelles. When used in combination with bioassays on intact organisms and precise, yet destructive analytical methods, the spatiotemporal resolution of sensors offers the prospect of a holistic understanding of nutrient flux in plants.

A learning curve for first trimester anatomy ultrasound in obese patients.

OBJECTIVES: A recent randomized controlled trial of first-trimester anatomy ultrasound in obese women found some advantages to using this technique in this population, but some aspects of feasibility were not clear, such as whether first-trimester ultrasound can be brought outside of a research setting. The learning curve for first-trimester anatomy has been described in the general population, but a learning curve has not been described for this technique in obese patients. This study sought to describe a learning curve for first-trimester anatomy ultrasounds in obese patients in an operator familiar with the basics of first-trimester imaging. DESIGN: This was a secondary analysis of the EASE-O pilot randomized controlled trial (NCT04639973), which recruited 128 women with a BMI≥35 kg/m2 and randomized them into two groups based on the timing of the first evaluation of fetal anatomy, to compare the completion rate of first- and second-trimester anatomy ultrasound. PARTICIPANTS: Pregnant women with a BMI≥35 kg/m2 Setting: January 2021 and February 2022 at maternal-fetal medicine clinics in Houston, Texas Methods: This secondary analysis evaluated data on the completion rate of first-trimester scans from the parent trial. Scans were grouped into bin sizes of 3, and prop_model for R version 4.2.0 for Windows was used to generate a learning curve across the first 60 scans. RESULTS: The parent study included 60 scans performed by one imager who had previously only done first-trimester scans in lean patients for limited anatomy. The probability of a complete scan increased over 60 scans from 0.38 to 0.69; 29 scans were required to reach the final probability, after which only marginal improvement followed. LIMITATIONS: The major limitation is the inclusion of only one operator for this curve. CONCLUSIONS: For an ultrasound operator with basic familiarity in first-trimester imaging, approximately 30 scans are needed to acquire a completion rate of 70% for detailed first trimester anatomy in women with BMI ≥35 kg/m2. This can be used in education and training programs focused on imaging in the first trimester.

Under Stress: Searching for Genes Involved in the Response of Abies pinsapo Boiss to Climate Change.

Currently, Mediterranean forests are experiencing the deleterious effects of global warming, which mainly include increased temperatures and decreased precipitation in the region. Relict Abies pinsapo fir forests, endemic in the southern Iberian Peninsula, are especially sensitive to these recent environmental disturbances, and identifying the genes involved in the response of this endangered tree species to climate-driven stresses is of paramount importance for mitigating their effects. Genomic resources for A. pinsapo allow for the analysis of candidate genes reacting to warming and aridity in their natural habitats. Several members of the complex gene families encoding late embryogenesis abundant proteins (LEAs) and heat shock proteins (HSPs) have been found to exhibit differential expression patterns between wet and dry seasons when samples from distinct geographical locations and dissimilar exposures to the effects of climate change were analyzed. The observed changes were more perceptible in the roots of trees, particularly in declining forests distributed at lower altitudes in the more vulnerable mountains. These findings align with previous studies and lay the groundwork for further research on the molecular level. Molecular and genomic approaches offer valuable insights for mitigating climate stress and safeguarding this endangered conifer.

Sponging of glutamate at the outer plasma membrane surface reveals roles for glutamate in development.

Plants use electrical and chemical signals for systemic communication. Herbivory, for instance, appears to trigger local apoplasmic glutamate accumulation, systemic electrical signals, and calcium waves that travel to report insect damage to neighboring leaves and initiate defense. To monitor extra- and intracellular glutamate concentrations in plants, we generated Arabidopsis lines expressing genetically encoded fluorescent glutamate sensors. In contrast to cytosolically localized sensors, extracellularly displayed variants inhibited plant growth and proper development. Phenotypic analyses of high-affinity display sensor lines revealed that root meristem development, particularly the quiescent center, number of lateral roots, vegetative growth, and floral architecture were impacted. Notably, the severity of the phenotypes was positively correlated with the affinity of the display sensors, intimating that their ability to sequester glutamate at the surface of the plasma membrane was responsible for the defects. Root growth defects were suppressed by supplementing culture media with low levels of glutamate. Together, the data indicate that sequestration of glutamate at the cell surface either disrupts the supply of glutamate to meristematic cells and/or impairs localized glutamatergic signaling important for developmental processes.

Using Medicare Annual Wellness Visits and telehealth to enhance ambulatory geriatrics education among medical students.

The Medicare Annual Wellness visit (AWV) was mandated as a fully covered benefit for older adults to enhance preventive care and improve healthcare outcomes. Although the benefit of conducting AWV is proven, its adoption in primary care is far from universal. The COVID-19 pandemic affected medical education and clinical care in unprecedented ways. Telehealth became a prominent way of delivering healthcare. Older adults, being significantly affected by the pandemic-related mortality and morbidity, were less likely to engage in preventive care with their healthcare providers. Amidst this considerable shift, we conceptualized a clinical experience for third-year medical students during their Ambulatory Care - Geriatrics clerkship that involved a telehealth interaction with an older adult to review AWV components, followed by an in-person office visit with the geriatrician preceptor. Post-session survey data highlighted the beneficial effect on student learning about older adult health maintenance, immunizations and geriatric syndrome assessment. It also facilitated self-directed learning and increased student-patient rapport. Preceptors appreciated the additional elements of care identified by the telehealth call that would otherwise not have been addressed in a time-limited office visit. This hybrid clinical experience reduced crowding in ambulatory clinical space during the COVID-19 pandemic, yet enhanced learning for students in geriatrics preventive care.

Navigating the Cancer Screening Decision for Patients with Dementia.

PURPOSE OF REVIEW: The risks of developing cancer and dementia both increase with age, giving rise to the complex question of whether continued cancer screening for older dementia patients is appropriate. This paper offers a practice-based clinical approach to determine an answer to this challenging question. RECENT FINDINGS: There is no consensus on the prevalence of cancer and dementia as co-diagnoses. Persons with dementia are screened less often compared to those without dementia. There is significant literature focusing on screening in the geriatric population, but there is little evidence to support decision-making for screening for older patients with dementia. Given this lack of evidence, individualized decisions should be made in collaboration with patients and family caregivers. Four considerations to help guide this process include prognosis, behavioral constraints, cognitive capacity, and goals for care. Future research will be challenging due to variability of factors that inform screening decisions and the vulnerable nature of this patient population.

For-profit hospitals as anchor institutions in the United States: a study of organizational stability.

BACKGROUND: Anchor institutions, by definition, have a long-term presence within their local communities, but it is uncertain as to whether for-profit hospitals meet this definition; most research on anchor institutions to date has been limited to nonprofit organizations such as hospitals and universities. Accordingly, this study aims to determine whether for-profit hospitals are stable enough to fulfill the role of anchor institutions through a long-term presence in communities which may help to stabilize local economies. METHODS: This longitudinal study analyzes national, secondary data between 2008 and 2017 compiled from the Dartmouth Atlas of Health Care, the American Hospital Association Annual Survey, and County Health Rankings. We use descriptive statistics to calculate the number of closures and mergers of hospitals of different ownership type, as well as staffing levels. Using logistic regression, we also assessed whether for-profit hospitals had higher odds of closing and merging, controlling for both organization and community factors. RESULTS: We found for-profit hospitals to be less stable than their public and nonprofit hospital counterparts, experiencing disproportionately more closures and mergers over time, with a multivariable analysis indicating a statistically significant difference. Furthermore, for-profit hospitals have fewer full-time employees relative to their size than hospitals of other ownership types, as well as lower total payroll expenditures. CONCLUSIONS: Study findings suggest that for-profit hospitals operate more efficiently in terms of expenses, but this also may translate into a lower level of economic contributions to the surrounding community through employment and purchasing initiatives. For-profit hospitals may also not have the stability required to serve as long-standing anchor institutions. Future studies should consider whether for-profit hospitals make other types of community investments to offset these deficits and whether policy changes can be employed to encourage anchor activities from local businesses such as hospitals.

Ancestral origin of ApoE ε4 Alzheimer disease risk in Puerto Rican and African American populations.

The ApoE ε4 allele is the most significant genetic risk factor for late-onset Alzheimer disease. The risk conferred by ε4, however, differs across populations, with populations of African ancestry showing lower ε4 risk compared to those of European or Asian ancestry. The cause of this heterogeneity in risk effect is currently unknown; it may be due to environmental or cultural factors correlated with ancestry, or it may be due to genetic variation local to the ApoE region that differs among populations. Exploring these hypotheses may lead to novel, population-specific therapeutics and risk predictions. To test these hypotheses, we analyzed ApoE genotypes and genome-wide array data in individuals from African American and Puerto Rican populations. A total of 1,766 African American and 220 Puerto Rican individuals with late-onset Alzheimer disease, and 3,730 African American and 169 Puerto Rican cognitively healthy individuals (> 65 years) participated in the study. We first assessed average ancestry across the genome ("global" ancestry) and then tested it for interaction with ApoE genotypes. Next, we assessed the ancestral background of ApoE alleles ("local" ancestry) and tested if ancestry local to ApoE influenced Alzheimer disease risk while controlling for global ancestry. Measures of global ancestry showed no interaction with ApoE risk (Puerto Rican: p-value = 0.49; African American: p-value = 0.65). Conversely, ancestry local to the ApoE region showed an interaction with the ApoE ε4 allele in both populations (Puerto Rican: p-value = 0.019; African American: p-value = 0.005). ApoE ε4 alleles on an African background conferred a lower risk than those with a European ancestral background, regardless of population (Puerto Rican: OR = 1.26 on African background, OR = 4.49 on European; African American: OR = 2.34 on African background, OR = 3.05 on European background). Factors contributing to the lower risk effect in the ApoE gene ε4 allele are likely due to ancestry-specific genetic factors near ApoE rather than non-genetic ethnic, cultural, and environmental factors.

The gene expression landscape of pine seedling tissues.

Conifers dominate vast regions of the Northern hemisphere. They are the main source of raw materials for timber industry as well as a wide range of biomaterials. Despite their inherent difficulties as experimental models for classical plant biology research, the technological advances in genomics research are enabling fundamental studies on these plants. The use of laser capture microdissection followed by transcriptomic analysis is a powerful tool for unravelling the molecular and functional organization of conifer tissues and specialized cells. In the present work, 14 different tissues from 1-month-old maritime pine (Pinus pinaster) seedlings have been isolated and their transcriptomes analysed. The results increased the sequence information and number of full-length transcripts from a previous reference transcriptome and added 39 841 new transcripts. In total, 2376 transcripts were ubiquitously expressed in all of the examined tissues. These transcripts could be considered the core 'housekeeping genes' in pine. The genes have been clustered in function to their expression profiles. This analysis reduced the number of profiles to 38, most of these defined by their expression in a unique tissue that is much higher than in the other tissues. The expression and localization data are accessible at ConGenIE.org (http://v22.popgenie.org/microdisection/). This study presents an overview of the gene expression distribution in different pine tissues, specifically highlighting the relationships between tissue gene expression and function. This transcriptome atlas is a valuable resource for functional genomics research in conifers.

Mechanism of Action of Miltefosine on Leishmania donovani Involves the Impairment of Acidocalcisome Function and the Activation of the Sphingosine-Dependent Plasma Membrane Ca2+ Channel.

Leishmania donovani is the causing agent of visceral leishmaniasis, a common infection that affects millions of people from the most underdeveloped countries. Miltefosine is the only oral drug to treat infections caused by L. donovani Nevertheless, its mechanism of action is not well understood. While miltefosine inhibits the synthesis of phosphatidylcholine and also affects the parasite mitochondrion, inhibiting the cytochrome c oxidase, it is to be expected that this potent drug also produces its effect through other targets. In this context, it has been reported that the disruption of the intracellular Ca2+ homeostasis represents an important object for the action of drugs in trypanosomatids. Recently, we have described a plasma membrane Ca2+ channel in Leishmania mexicana, which is similar to the L-type voltage-gated Ca2+ channel (VGCC) present in humans. Remarkably, the parasite Ca2+ channel is activated by sphingosine, while the L-type VGCC is not affected by this sphingolipid. In the present work we demonstrated that, similarly to sphingosine, miltefosine is able to activate the plasma membrane Ca2+ channel from L. donovani Interestingly, nifedipine, the classical antagonist of the human channel, was not able to fully block the parasite plasma membrane Ca2+ channel, indicating that the mechanism of interaction is not identical to that of sphingosine. In this work we also show that miltefosine is able to strongly affect the acidocalcisomes from L. donovani, inducing the rapid alkalinization of these important organelles. In conclusion, we demonstrate two new mechanisms of action of miltefosine in L. donovani, both related to disruption of parasite Ca2+ homeostasis.

Anti-Trypanosoma cruzi action of a new benzofuran derivative based on amiodarone structure.

Chagas disease is a neglected tropical affection caused by the protozoan parasite Trypanosoma cruzi. There is no current effective treatment since the only two available drugs have a limited efficacy and produce side effects. Thus, investigation efforts have been directed to the identification of new drug leads. In this context, Ca2+ regulating mechanisms have been postulated as targets for antiparasitic compounds, since they present paramount differences when compared to host cells. Amiodarone is an antiarrhythmic with demonstrated trypanocidal activity acting through the disruption of the parasite intracellular Ca2+ homeostasis. We now report the effect of a benzofuran derivative based on the structure of amiodarone on T. cruzi. This derivative was able to inhibit the growth of epimastigotes in culture and of amastigotes inside infected cells, the clinically relevant phase. We also show that this compound, similarly to amiodarone, disrupts Ca2+ homeostasis in T. cruzi epimastigotes, via two organelles involved in the intracellular Ca2+ regulation and the bioenergetics of the parasite. We demonstrate that the benzofuran derivative was able to totally collapse the membrane potential of the unique giant mitochondrion of the parasite and simultaneously produced the alkalinization of the acidocalcisomes. Both effects are evidenced by a large increase in the intracellular Ca2+ concentration of T. cruzi.

Molecular fundamentals of nitrogen uptake and transport in trees.

Nitrogen (N) is frequently a limiting factor for tree growth and development. Because N availability is extremely low in forest soils, trees have evolved mechanisms to acquire and transport this essential nutrient along with biotic interactions to guarantee its strict economy. Here we review recent advances in the molecular basis of tree N nutrition. The molecular characteristics, regulation, and biological significance of membrane proteins involved in the uptake and transport of N are addressed. The regulation of N uptake and transport in mycorrhized roots and transcriptome-wide studies of N nutrition are also outlined. Finally, several areas of future research are suggested.

Poplar trees for phytoremediation of high levels of nitrate and applications in bioenergy.

The utilization of high amounts of nitrate fertilizers for crop yield leads to nitrate pollution of ground and surface waters. In this study, we report the assimilation and utilization of nitrate luxuriant levels, 20 times more than the highest N fertilizer application in Europe, by transgenic poplars overexpressing a cytosolic glutamine synthetase (GS1). In comparison with the wild-type controls, transgenic plants grown under high N levels exhibited increased biomass (171.6%) and accumulated higher levels of proteins, chlorophylls and total sugars such as glucose, fructose and sucrose. These plants also exhibited greater nitrogen-use efficiency particularly in young leaves, suggesting that they are able to translocate most of the resources to the above-ground part of the plant to produce biomass. The transgenic poplar transcriptome was greatly affected in response to N availability with 1237 genes differentially regulated in high N, while only 632 genes were differentially expressed in untransformed plants. Many of these genes are essential in the adaptation and response against N excess and include those involved in photosynthesis, cell wall formation and phenylpropanoid biosynthesis. Cellulose production in the transgenic plants was fivefold higher than in control plants, indicating that transgenic poplars represent a potential feedstock for applications in bioenergy. In conclusion, our results show that GS transgenic poplars can be used not only for improving growth and biomass production but also as an important resource for potential phytoremediation of nitrate pollution.

Deciphering the molecular basis of ammonium uptake and transport in maritime pine.

Ammonium is the predominant form of inorganic nitrogen in the soil of coniferous forests. Despite the ecological and economic importance of conifers, the molecular basis of ammonium uptake and transport in this group of gymnosperms is largely unknown. In this study, we describe the functional characterization of members of the AMT gene family in Pinus pinaster: PpAMT1.1, PpAMT1.2 and PpAMT1.3 (subfamily 1) and PpAMT2.1 and PpAMT2.3 (subfamily 2). Our phylogenetic analysis indicates that in conifers, all members of the AMT1 subfamily evolved from a common ancestor that is evolutionarily related to the ancient PpAMT1.2 gene. Individual AMT genes are developmentally and nutritionally regulated, and their transcripts are specifically distributed in different organs. PpAMT1.3 was predominantly expressed in the roots, particularly during N starvation and mycorrhizal interaction, whereas PpAMT2.3 was preferentially expressed in lateral roots. Immunolocalization studies of roots with varied nitrogen availability revealed that PpAMT1 and PpAMT2 proteins play complementary roles in the uptake of external ammonium. Heterologous expression in yeast and Xenopus oocytes revealed that the AMT genes encode functional transporters with different kinetics and with different capacities for ammonium transport. Our results provide new insights on how nitrogen is acquired and transported in conifers.

SQ109, a new drug lead for Chagas disease.

We tested the antituberculosis drug SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, for its in vitro activity against the trypanosomatid parasite Trypanosoma cruzi, the causative agent of Chagas disease. SQ109 was found to be a potent inhibitor of the trypomastigote form of the parasite, with a 50% inhibitory concentration (IC50) for cell killing of 50 ± 8 nM, but it had little effect (50% effective concentration [EC50], ∼80 µM) in a red blood cell hemolysis assay. It also inhibited extracellular epimastigotes (IC50, 4.6 ± 1 µM) and the clinically relevant intracellular amastigotes (IC50, ∼0.5 to 1 µM), with a selectivity index of ∼10 to 20. SQ109 caused major ultrastructural changes in all three life cycle forms, as observed by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It rapidly collapsed the inner mitochondrial membrane potential (Δψm) in succinate-energized mitochondria, acting in the same manner as the uncoupler FCCP [carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone], and it caused the alkalinization of internal acidic compartments, effects that are likely to make major contributions to its mechanism of action. The compound also had activity against squalene synthase, binding to its active site; it inhibited sterol side-chain reduction and, in the amastigote assay, acted synergistically with the antifungal drug posaconazole, with a fractional inhibitory concentration index (FICI) of 0.48, but these effects are unlikely to account for the rapid effects seen on cell morphology and cell killing. SQ109 thus most likely acts, at least in part, by collapsing Δψ/ΔpH, one of the major mechanisms demonstrated previously for its action against Mycobacterium tuberculosis. Overall, the results suggest that SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, may also have potential as a drug lead against Chagas disease.

Redundancy and metabolic function of the glutamine synthetase gene family in poplar.

BACKGROUND: Glutamine synthetase (GS; EC: 6.3.1.2, L-glutamate: ammonia ligase ADP-forming) is a key enzyme in ammonium assimilation and metabolism in higher plants. In poplar, the GS family is organized in 4 groups of duplicated genes, 3 of which code for cytosolic GS isoforms (GS1.1, GS1.2 and GS1.3) and one group that codes for the choroplastic GS isoform (GS2). Our previous work suggested that GS duplicates may have been retained to increase the amount of enzyme in a particular cell type. RESULTS: The current study was conducted to test this hypothesis by developing a more comprehensive understanding of the molecular and biochemical characteristics of the poplar GS isoenzymes and by determinating their kinetic parameters. To obtain further insights into the function of the poplar GS genes, in situ hybridization and laser capture microdissections were conducted in different tissues, and the precise GS gene spatial expression patterns were determined in specific cell/tissue types of the leaves, stems and roots. The molecular and functional analysis of the poplar GS family and the precise localization of the corresponding mRNA in different cell types strongly suggest that the GS isoforms play non-redundant roles in poplar tree biology. Furthermore, our results support the proposal that a function of the duplicated genes in specific cell/tissue types is to increase the abundance of the enzymes. CONCLUSION: Taken together, our results reveal that there is no redundancy in the poplar GS family at the whole plant level but it exists in specific cell types where the two duplicated genes are expressed and their gene expression products have similar metabolic roles. Gene redundancy may contribute to the homeostasis of nitrogen metabolism in functions associated with changes in environmental conditions and developmental stages.