Nitrogen （N） is an essential macronutrient that affects plant growth and development. N is an important component of chlorophyll, amino acids, nucleic acids, and secondary metabolites. Nitrate is one ...of the most abundant N sources in the soil. Because nitrate and other N nutrients are often limiting, plants have developed sophisticated mechanisms to ensure adequate supply of nutrients in a variable environment. Nitrate is absorbed in the root and mobilized to other organs by nitrate transporters. Nitrate sensing activates signaling pathways that impinge upon molecular, metabolic, physiological, and developmental responses locally and at the whole plant level. With the advent of genomics technologies and genetic tools, important advances in our understanding of nitrate and other N nutrient responses have been achieved in the past decade. Furthermore, techniques that take advantage of natural polymor- phisms present in divergent individuals from a single species have been essential in uncovering new components. However, there are still gaps in our understanding of how nitrate signaling affects biolog- ical processes in plants. Moreover, we still lack an integrated view of how all the regulatory factors iden- tified interact or crosstalk to orchestrate the myriad N responses plants typically exhibit. In this review, we provide an updated overview of mechanisms by which nitrate is sensed and transported throughout the plant. We discuss signaling components and how nitrate sensing crosstalks with hormonal pathways for developmental responses locally and globally in the plant. Understanding how nitrate impacts on plant metabolism, physiology, and growth and development in plants is key to improving crops for sustainable agriculture.
•Nitrate modulates hormonal pathways to adapt plant biology to environmental cues.•Hormones participate in local and systemic nitrogen signaling to regulate root and shoot growth.•Nitrate ...availability crosstalk with hormones to influence root system architecture.•This nitrate:hormone crosstalk also influences metabolism, uptake and stress responses.•Nitrate delays flowering time via the gibberellin signaling pathway.
Nitrate is an essential macronutrient for plants, a primary nitrogen source in natural and human-made ecosystems. Nitrate can also act as a signaling molecule that directs genome-wide gene expression changes with an impact on plant metabolism, physiology, growth and development. Nitrate and phytohormone signaling pathways crosstalk to modulate growth and developmental programs in a multifactorial manner. Nitrate-signaling controls plant growth and development using molecular mechanisms that involve phytohormone-signaling pathways. In contrast, many phytohormones modulate or impact nitrate signaling in interconnected pathways. In this review, we explore recent progress in our understanding of well-documented connections between nitrate and phytohormones such as auxin, cytokinin and abscisic acid. We also discuss recent studies connecting nitrate to other phytohormones such as ethylene, salicylic acid, gibberellins and brassinosteroids. While many molecular details remain to be elucidated, a number of core signaling components at the intersection between nitrate and the major hormonal pathways have been described. We focus on established interactions of nitrate and different hormonal pathways to bring about cellular, growth and developmental processes in Arabidopsis thaliana.
Several metals belong to a group of non-biodegradable inorganic constituents that, at low concentrations, play fundamental roles as essential micronutrients for the growth and development of plants. ...However, in high concentrations they can have toxic and/or mutagenic effects, which can be counteracted by natural chemical compounds called chelators. Chelators have a diversity of chemical structures; many are organic acids, including carboxylic acids and cyclic phenolic acids. The exogenous application of such compounds is a non-genetic approach, which is proving to be a successful strategy to reduce damage caused by heavy metal toxicity. In this review, we will present the latest literature on the exogenous addition of both carboxylic acids, including the Kreb's Cycle intermediates citric and malic acid, as well as oxalic acid, lipoic acid, and phenolic acids (gallic and caffeic acid). The use of two non-traditional organic acids, the phytohormones jasmonic and salicylic acids, is also discussed. We place particular emphasis on physiological and molecular responses, and their impact in increasing heavy metal tolerance, especially in crop species.
Discarded bamboo culms of Guadua chacoensis were used for biochar remediation of aqueous As(V). Raw biochar (BC), activated biochar (BCA), raw Fe3O4 nanoparticle-covered biochar (BC-Fe), and ...activated biochar covered with Fe3O4 nanoparticles (BCA-Fe) were prepared, characterized and tested for As(V) aqueous adsorption. The goal is to develop an economic, viable, and sustainable adsorbent to provide safe arsenic-free water. Adsorbents were characterized using scanning electron microscopy (SEM) and energy dispersive analysis by X-ray (SEM-EDX), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (TEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller surface area measurements (SBET), point of zero charge determinations (PZC), and elemental analysis. Activation with KOH increased the O/C ratio and the surface area of BC from 6.7 m2/g to 1239.7 m2/g (BCA). As(V) sorption equilibrium was achieved within <2 h for all four adsorbents and kinetics followed the pseudo-second-order model. At a 10 mg/L initial As(V) concentration, BC-Fe achieved a 100% removal (5 mg/g) over a pH 5 to 9 window. Sorption was endothermic on all four adsorbents and the capacities rose with the increasing temperature. Langmuir capacities at 40 °C for BC, BCA, BC-Fe, and BCA-Fe were 256, 217, 457, and 868 mg/g, respectively, and capacities were compared with other sorbents. Breakthrough fixed-bed column sorption was carried out for BC and BC-Fe producing 6.6 mg/g and 13.9 mg/g bed capacities, respectively. Potassium phosphate was a better As stripping agent than sodium bicarbonate. Performance of the adsorbents in an As(V)-spiked natural water and a naturally As(V)-contaminated domestic water were assessed. Robust arsenate sequestration occurred generating As-safe water (As <0.01 mg/L), despite the presence of competing ions. Stoichiometric precipitation of iron-arsenate complexes triggered by iron dissolution was also established.
Display omitted
•Hybrid bamboo biochar Fe3O4 sorbents were assessed for removal of As(V) from water.•Sorption capacities increased with temperature and ranged from 39 to 868 mg/g.•Iron-leaching and iron-arsenate stoichiometric precipitation contributed to uptake.•Capacities and iron-leaching remain unaltered at natural water pH's (5–9).•Competing ion sorption studies showed a preference for As.
Abstract
Nitrate can act as a potent signal to control growth and development in plants. In this study, we show that nitrate is able to stimulate primary root growth via increased meristem activity ...and cytokinin signaling. Cytokinin perception and biosynthesis mutants displayed shorter roots as compared with wild-type plants when grown with nitrate as the only nitrogen source. Histological analysis of the root tip revealed decreased cell division and elongation in the cytokinin receptor double mutant ahk2/ahk4 as compared with wild-type plants under a sufficient nitrate regime. Interestingly, a nitrate-dependent root growth arrest was observed between days 5 and 6 after sowing. Wild-type plants were able to recover from this growth arrest, while cytokinin signaling or biosynthesis mutants were not. Transcriptome analysis revealed significant changes in gene expression after, but not before, this transition in contrasting genotypes and nitrate regimes. We identified genes involved in both cell division and elongation as potentially important for primary root growth in response to nitrate. Our results provide evidence linking nitrate and cytokinin signaling for the control of primary root growth in Arabidopsis thaliana.
Premise of research. Chusquea Kunth is the most diverse bamboo genus worldwide and comprises 198 species classified into five subgenera. Chusquea subg. Magnifoliae and Chusquea subg. Platonia ...together include 26 taxa that have been studied on the basis of incomplete or fragmentary material, and complete keys to their taxonomic identification based on vegetative and reproductive characters are still pending. Since the identification of woody bamboos often relies mainly on vegetative characters, the addition of foliage leaf blade anatomy and micromorphology characters provides valuable information to be considered.
Methodology. Anatomical and micromorphological studies were performed on the basis of herbarium material. Foliage leaf blade abaxial epidermal and transverse section characters are described and compared for 11 taxa of Chusquea subg. Magnifoliae and 14 of Chusquea subg. Platonia to enhance the currently available descriptions.
Pivotal results. Regarding foliage leaf blade anatomy in transverse section, no single character turned out to be exclusive to a species or subgenus. All taxa studied here are recognizable from a combination of anatomical characters. Of note is that intercostal sclerenchyma is recorded for the first time in the subtribe Chusqueinae. When micromorphological characters of the foliage leaf blade abaxial epidermis are considered, a few potential autapomorphies may be recognized for a few species.
Conclusions. On the basis of anatomical and micromorphological studies, characters of taxonomic value are presented in comparative tables. A key to the identification of the species of Chusquea subg. Magnifoliae and Chusquea subg. Platonia was elaborated and is presented here for the first time as an additional tool to corroborate the taxonomic identity of sterile or poorly collected specimens.
Chronic obstructive pulmonary disease (COPD) is prevalent in patients infected with HIV. The purpose of this study was to test the hypothesis that systemic oxidation correlates with loss of lung ...function in subjects with COPD, and that HIV infection can contribute to creating such an environment. Subjects were recruited at the University of Louisville in the following groups: HIV-infected (n = 36), COPD (n = 32), HIV and COPD (n = 28), and uninfected controls with normal lung function (n = 34). HIV infection was assessed by viral load and CD4 cell counts. Pulmonary function was determined by spirometry, and plasma was collected for measurement of cysteine (Cys), cystine (CySS), glutathione (GSH) and GSH disulfide (GSSG) by HPLC followed by estimation of redox potentials (Eh) using the Nernst equation. Results showed that patients with COPD had more oxidized plasma Eh Cys/CySS than patients with normal lung function, but plasma Eh GSH/GSSG was unaltered. In addition, there was a correlation between the extent of plasma Eh Cys/CySS oxidation and loss of lung function, and this correlation remained even after correcting for age, sex, race and body mass index. HIV infection per se was not associated with increased oxidation of plasma Eh Cys/CySS, but plasma Eh Cys/CySS was more oxidized in patients with lower CD4-positve T cell counts. In patients with both HIV infection and COPD, there was a significant correlation between CD4 cell counts and lung function. Thus, systemic oxidation correlated with decreased lung function in subjects with COPD and decreased CD4 counts in subjects infected with HIV. Thus, factors contributing to plasma Eh Cys/CySS may represent novel mechanisms underlying the increased prevalence of COPD in people living with HIV.
Display omitted
•COPD is a major cause of morbidity and mortality in patients infected with HIV.•Oxidative stress has been implicated in the pathogenesis of both COPD and HIV.•Decreased lung function and CD4 counts paralleled oxidation of plasma cysteine/cystine redox potential (Eh Cys/CySS).•Plasma Eh Cys/CySS is a marker of oxidative stress that may be used to identify subjects at risk for lung function decline.
The 2017 North Atlantic hurricane season brought many of the injustices faced by non‐sovereign Caribbean States to the fore. These injustices, which positioned Caribbean people as expendable to ...colonial powers, highlighted the impact of historically enduring colonial structures of non‐sovereignty on post‐hurricane response and recovery efforts across the region. In this paper, we argue that Puerto Rico's status as a Commonwealth of the United States (U.S.) influenced the nature and outcome of the U.S. Federal Government's response to Hurricane Maria in 2017. Its response was marked by unnecessary delays, silence, and the withholding of information, and the prioritisation of bureaucracy, evidencing the disposability of Black and brown lives and bodies, and signalling the need to collectively leverage the power of an environmental justice agenda. For this to be achieved, we further argue, a people's right to sovereignty and indispensability must be centred.
Short
In this paper, we argue that Puerto Rico's status as a Commonwealth of the United States (U.S.) influenced the nature and outcome of the U.S. Federal Government's response to Hurricane Maria in 2017. Its response was marked by unnecessary delays, silence, and the withholding of information, and the prioritisation of bureaucracy, evidencing the disposability of Black and brown lives and bodies, and signalling the need to collectively leverage the power of an environmental justice agenda. For this to be achieved, we further argue, a people's right to sovereignty and indispensability must be centred.
Plant growth-promoting rhizobacteria (PGPR) induce positive effects in plants, such as increased growth or reduced stress susceptibility. The mechanisms behind PGPR/plant interaction are poorly ...understood, as most studies have described short-term responses on plants and only a few studies have analyzed plant molecular responses under PGPR colonization. Here, we studied the effects of the PGPR bacterial model Burkholderiaphytofirmans PsJN on the whole life cycle of Arabidopsis thaliana plants. We reported that at different plant developmental points, strain PsJN can be found in the rhizosphere and also colonizing their internal tissues. In early ontogeny, strain PsJN increased several growth parameters and accelerated growth rate of the plants. Also, an Arabidopsis transcriptome analysis revealed that 408 genes showed differential expression in PsJN-inoculated plants; some of these genes are involved in stress response and hormone pathways. Specifically, genes implicated in auxin and gibberellin pathways were induced. Quantitative transcriptional analyses of selected genes in different developmental stages revealed that the beginning of these changes could be evidenced early in development, especially among the down-regulated genes. The inoculation with heat-killed bacteria provoked a more severe transcriptional response in plants, but was not able to induce plant growth-promotion. Later in ontogeny, the growth rates of inoculated plants decreased with respect to the non-inoculated group and, interestingly, the inoculation accelerated the flowering time and the appearance of senescence signs in plants; these modifications correlate with the early up-regulation of flowering control genes. Then, we show that a single inoculation with a PGPR could affect the whole life cycle of a plant, accelerating its growth rate and shortening its vegetative period, both effects relevant for most crops. Thus, these findings provide novel and interesting aspects of these relevant biological interactions.
OBJECTIVES
To define the current incidence, epidemiology, and mortality of older adult patients hospitalized with community‐acquired pneumonia (CAP) in Louisville, KY and thus estimate the burden of ...CAP in the older adult population of the United States. To define risk factors associated with early and late outcomes.
DESIGN
This was a secondary analysis of older adults (aged ≥65 years) from the University of Louisville Pneumonia Study, a prospective population‐based cohort study of all hospitalized adults with CAP between June 1, 2014, and May 31, 2016.
SETTING
The study took place in all nine acute care hospitals for adults in Louisville, KY.
PARTICIPANTS
Residents in the city of Louisville, KY, who were diagnosed with CAP between the inclusion dates were included and who were aged 65 years or older.
MEASUREMENTS
Incidence of CAP and outcomes were measured. A total of nine risk factors were also assessed for any potential association with time to clinical stability, length of stay (LOS), and mortality.
RESULTS
During the 2‐year study, from a Louisville population of 102 264 adults aged 65 years or older, 4760 were hospitalized with CAP. The incidence of older adults hospitalized with CAP was 2093 per 100 000 population. This corresponds to 967 470 older adults in the United States hospitalized per year with CAP. The median time to clinical stability was 2 days, and the median LOS was 6 days. The 30‐day all‐cause mortality was 17%. The 1‐year all‐cause mortality was 38% (829 patients), which corresponds to 361 982 deaths in the United States with CAP in older adults.
CONCLUSION
The estimated burden of CAP in older adults is substantial in the United States. Nearly 1 million older adults are hospitalized for CAP, and over a third of those die within 1 year. J Am Geriatr Soc 68:1007–1014, 2020
PDF
