Secondary metabolites responses of plants exposed to ozone: an update

Tropospheric ozone (O3) is a secondary pollutant that causes oxidative stress in plants due to the generation of excess reactive oxygen species (ROS). Phenylpropanoid metabolism is induced as a usual response to stress in plants, and induction of key enzyme activities and accumulation of secondary metabolites occur, upon O3 exposure to provide resistance or tolerance. The phenylpropanoid, isoprenoid, and alkaloid pathways are the major secondary metabolic pathways from which plant defense metabolites emerge. Chronic exposure to O3 significantly accelerates the direction of carbon flows toward secondary metabolic pathways, resulting in a resource shift in favor of the synthesis of secondary products. Furthermore, since different cellular compartments have different levels of ROS sensitivity and metabolite sets, intracellular compartmentation of secondary antioxidative metabolites may play a role in O3-induced ROS detoxification. Plants' responses to resource partitioning often result in a trade-off between growth and defense under O3 stress. These metabolic adjustments help the plants to cope with the stress as well as for achieving new homeostasis. In this review, we discuss secondary metabolic pathways in response to O3 in plant species including crops, trees, and medicinal plants; and how the presence of this stressor affects their role as ROS scavengers and structural defense. Furthermore, we discussed how O3 affects key physiological traits in plants, foliar chemistry, and volatile emission, which affects plant-plant competition (allelopathy), and plant-insect interactions, along with an emphasis on soil dynamics, which affect the composition of soil communities via changing root exudation, litter decomposition, and other related processes.

Arabidopsis plants overexpressing additional copies of heat shock protein Hsp101 showed high heat tolerance and endo-gene silencing

Hsp101 chaperone is vital for survival of plants under heat stress. We generated transgenic Arabidopsis thaliana (Arabidopsis) lines with extra copies of Hsp101 gene using diverse approaches. Arabidopsis plants transformed with rice Hsp101 cDNA driven by Arabidopsis Hsp101 promoter (IN lines) showed high heat tolerance while the plants transformed with rice Hsp101 cDNA driven by CaMV35S promoter (C lines) were like wild type plants in heat stress response. Transformation of Col-0 plants with 4633 bp Hsp101 genomic fragment (GF lines) from A. thaliana containing both its coding and the regulatory sequence resulted in mostly over-expressor (OX) lines and a few under-expressor (UX) lines of Hsp101. OX lines showed enhanced heat tolerance while the UX lines were overly heat sensitive. In UX lines, silencing of not only Hsp101 endo-gene was noted but also transcript of choline kinase (CK2) was silenced. Previous work established that in Arabidopsis, CK2 and Hsp101 are convergent gene pairs sharing a bidirectional promoter. The elevated AtHsp101 protein amount in most GF and IN lines was accompanied by lowered CK2 transcript levels under HS. We observed increased methylation of the promoter and gene sequence region in UX lines; however, methylation was lacking in OX lines.

A single centre evaluation of risk prediction models and imaging modalities in acute appendicitis

INTRODUCTION

Patients with suspected appendicitis remain a diagnostic challenge. The aim of this study was to validate risk prediction models, and to investigate diagnostic accuracy of ultrasonography and computed tomography (CT) in adults undergoing appendicectomy.

METHODS

A retrospective case review was performed of patients aged 16-45 years having an appendicectomy between January 2019 and January 2020 at a tertiary referral centre. Primary outcomes were the accuracy of a high risk appendicitis risk score and ultrasonography and CT imaging modalities compared with histological reports following appendicectomy.

RESULTS

A total of 206 patients (52% female) were included in the study. Removal of a histologically normal appendix was equally likely in men and women (13.1% vs 11.2% respectively, relative risk: 1.17, 95% confidence interval: 0.56-2.44, p=0.674). A high risk appendicitis score correctly identified 84.0% (79/94) of cases in men and 85.9% (67/78) of cases in women. Ultrasonography was reported as equivocal in 85.7% (18/21) of low risk women and 59.0% (23/39) of high risk women. CT correctly detected or excluded appendicitis in 75.0% (6/8) of low risk women and 88.5% (23/26) of high risk women.

CONCLUSIONS

This study suggests that risk prediction models may be useful in both women and men to identify appendicitis. Ultrasonography gave high rates of equivocal results and should not be relied on for the diagnosis of appendicitis. CT is a highly accurate diagnostic tool and could be considered in those at low risk where clinical suspicion remains to reduce negative appendicectomy rates.

Ascorbic acid and thiols as potential biomarkers of ozone tolerance in tropical wheat cultivars

Tropospheric ozone (O₃) has been identified as the most damaging air pollutant to crop plants in terms of growth and yield reductions. Considering the negative effect of O₃ in tropical regions, fourteen commonly grown Indian wheat cultivars with known sensitivity to O₃ were tested for their sensitivity/tolerance with respect to two major antioxidants (ascorbic acid and thiols) and grain yield responses against elevated O₃ (ambient + 30 ppb) exposure. The objectives of the study were to assess the usefulness of the biochemical markers in the screening of wheat cultivars having differential level of sensitivity to O₃ and different release time (modern and old cultivars). Ozone exposure led to an upsurge of ascorbic acid, thiols as well as their ratio greatly in the tolerant group followed by the intermediately sensitive group while least in sensitive one. Both ascorbic acid and thiol contents offered more resistance to early released cultivars compared to modern ones. Ascorbic acid served to be the most influential parameter for determining varietal response under elevated O₃ stress and directly linked with O₃ tolerance. Overall, the sensitive group suffered maximum yield losses while the minimum was observed in the tolerant group due to the differential enhancement of tolerance offered by antioxidants. Higher concentrations of antioxidants at early growth stages were highly correlated with final yield responses suggesting the role of antioxidants as a determinant of final yield. Findings of this study will help in the identification of O₃ tolerant and sensitive wheat cultivars for future screening programs using ascorbic acid and thiols as important markers of O₃ tolerance.

Assessment of Ozone Sensitivity in Three Wheat Cultivars Using Ethylenediurea

Three wheat (Triticum aestivum L.) cultivars [HD 2987 (ozone (O₃) sensitive), PBW 502 (intermediately sensitive) and Kharchiya 65 (O₃ tolerant)] with known sensitivity to O₃ were re-evaluated using ethylenediurea (EDU; 400 ppm) to ascertain the use of EDU in determiningO₃ sensitivity under highly O₃-polluted tropical environments. EDU treatment helped in improving the growth, biomass, photosynthetic pigments and the antioxidative defense system of all the wheat cultivars. Under EDU treatment, PBW 502 retained more biomass, while HD 2987 showed better performance and ultimately the greatest increment in yield. Cultivar Kharchiya 65 also showed a positive response to EDU as manifested with an increase in pigment contents, total biomass and enzymatic antioxidants; however, this increment was comparatively lower compared to the other two cultivars. The results indicated that EDU did not have many physiological effects on cultivars but helped in counteracting O₃ primarily by scavenging reactive oxygen species and enhancing the antioxidative defense system where superoxide dismutase emerged as the major responsive biochemical parameter against ambient O₃. The observed results clearly indicated that differential O₃ sensitivity in three wheat cultivars established by the previous study is in accordance with the present study using EDU as a sensitivity tool, which is an easy and efficient technology in comparison to chamber and Free-Air Carbon dioxide Enrichment (FACE) experiments although its mechanistic understanding needs to be further validated.

Assessment of ozone toxicity among 14 Indian wheat cultivars under field conditions: growth and productivity

Tropospheric ozone (O₃) is a well-known threat to global agricultural production. Wheat (Triticum aestivum L.) is the second most important staple crop in India, although little is known about intra-specific variability of Indian wheat cultivars in terms of their sensitivity against O₃. In this study, 14 wheat cultivars widely grown in India were exposed to 30 ppb elevated O₃ above ambient level using open top chambers to evaluate their response against O₃ stress. Different growth and physiological parameters, foliar injury and grain yield were evaluated to assess the sensitivity of cultivars and classified them on the basis of their cumulative stress response index (CSRI). Due to elevated O₃, growth parameters, plant biomass, and photosynthetic rates were negatively affected, whereas variable reductions in yield were observed among the test cultivars. Based on CSRI values, HD 2987, DBW 50, DBW 77, and PBW 550 were classified as O₃ sensitive; HD 2967, NIAW 34, HD 3059, PBW 502, HUW 213, and HUW 251 as intermediately sensitive, while HUW12, KUNDAN, HUW 55, and KHARCHIYA 65 were found to be O₃-tolerant cultivars. Cultivars released after year 2000 were found to be more sensitive compared to earlier released cultivars. Path analysis approach showed that leaf area, plant biomass, stomatal conductance, net assimilation rate, and absolute growth rate were the most important variables influencing yield under O₃ stress. Findings of the current study highlight the importance of assessing differential sensitivity and tolerance of wheat cultivars and response of different traits in developing resistance against elevated O₃.

Tropospheric ozone pollution in India: effects on crop yield and product quality

Ozone (O₃) in troposphere is the most critical secondary air pollutant, and being phytotoxic causes substantial losses to agricultural productivity. Its increasing concentration in India particularly in Indo-Gangetic plains is an issue of major concern as it is posing a threat to agriculture. In view of the issue of rising surface level of O₃ in India, the aim of this compilation is to present the past and the prevailing concentrations of O₃ and its important precursor (oxides of nitrogen) over the Indian region. The resulting magnitude of reductions in crop productivity as well as alteration in the quality of the product attributable to tropospheric O₃ has also been taken up. Studies in relation to yield measurements have been conducted predominantly in open top chambers (OTCs) and also assessed by using antiozonant ethylene diurea (EDU). There is a substantial spatial difference in O₃ distribution at different places displaying variable O₃ concentrations due to seasonal and geographical variations. This review further recognizes the major information lacuna and also highlights future perspectives to get the grips with rising trend of ground level O₃ pollution and also to formulate the policies to check the emissions of O₃ precursors in India.

Cultivar specific variations in antioxidative defense system, genome and proteome of two tropical rice cultivars against ambient and elevated ozone

For the past few decades continuous increase in the levels of tropospheric ozone (O3) concentrations is posing to be a threat for agricultural productivity. Two high yielding tropical rice cultivars (Malviya dhan 36 and Shivani) were evaluated against different concentrations of O3 under field conditions. Experimental design included filtered chambers, non-filtered chambers having ambient O3 and 10 and 20ppb elevated O3 above the ambient. Study was conducted to assess differential response if any in induction of antioxidative defense system, genome stability, leaf proteome, yield and quality of the product in both the test cultivars. Superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR) were induced under ambient and elevated levels of O3. Native polyacrylamide gel electrophoresis (PAGE) of SOD, CAT and POD also displayed increased enzymatic activity along with associated alterations in specific isoforms. Ascorbic acid, thiols and phenolics were also stimulated at ambient and elevated O3. Structural alterations in DNA of rice plants due to O3 affecting its genome template stability (GTS) was examined using RAPD technique. 2-D PAGE revealed 25 differential spots in Malviya dhan 36 and 36 spots in Shivani after O3 treatment with reductions in RuBisCO subunits. Reductions in yield and change in the quality of grains were also noticed.

Assessment of ethylene diurea-induced protection in plants against ozone phytotoxicity

Urbanization, industrialization and unsustainable utilization of natural resources have made tropospheric ozone (03) one of the world's most significant air pollutants. Past studies reveal that 0 3 is a phytotoxic air pollutant that causes or enhances food insecurity across the globe. Plant sensitivity, tolerance and resistance to 0 3 involve a wide array of responses that range from growth to the physiological, biochemical and molecular. Although plants have an array of defense systems to combat oxidative stress from 0 3 exposure, they still suffer sizable yield reductions. In recent years, the ground-level 0 3 concentrations to which crop plants have been exposed have caused yield loses that are economically damaging. Several types of chemicals have been applied or used to mitigate the effects produced by 0 3 on plants. These include agrochemicals (fungicides, insecticides, plant growth regulators), natural antioxidants, and others. Such treatments have been effective to one degree to another, in ameliorating Or generated stress in plants. Ethylene diurea (EDU) has been the most effective protectant used and has also served as a monitoring agent for assessing plant yield losses from 0 3 exposure. In this review, we summarize the data on how EDU has been used, the treatment methods tested, and application doses found to be both protective and toxic in plants. We have also summarized data that address the nature and modes of action (biophysical and biochemical) of EDU. In general, the literature discloses that EDU is effective in reducing ozone damage to plants, and indicates that EDU should be more widely used on 0 3 sensitive plants as a tool for biomonitoring of 0 3 concentrations. Biomonitoring studies that utilize EDU are very useful for rural and remote areas and in developing countries where 0 3 monitoring is constrained from unavailability of electricity. The mechanism(s) by which EDU prevents 0 3 toxicity in plants is still not completely known. EDU possesses great utility for screening plant sensitivity under field conditions in areas that experience high 0 3 concentrations, because EDU prevents 0 3 toxicity only in 0 3 sensitive plants. Ozone-resistant plants do not respond positively to EDU applications. However, EDU application dose and frequency must be standardized before it can be effectively and widely used for screening 0 3 sensitivity in plants. EDU acts primarily by enhancing biochemical plant defense and delaying Or induced senescence, thereby reducing chlorophyll loss, and maintaining physiological efficiency and primary metabolites; these actions enhance growth, biomass and yield of plants. We believe that future studies are needed to better address the EDU dose response relationship for many plant species, and to screen for new cultivars that can resist 0 3 stress. Although some research on the physiological and biochemical mechanisms of action of EDU have been performed, the new 'omics' tools have not been utilized to evaluate EDUs mechanism of action. Such data are needed, as is gene expression and proteome profiling studies on EDU-treated and -untreated plants.

Investigating the response of tropical maize (Zea mays L.) cultivars against elevated levels of O3 at two developmental stages

Tropospheric ozone (O3) concentrations are rising in Indo-Gangetic plains of India, causing potential threat to agricultural productivity. Maize (Zea mays L.) is the third most important staple crop at global level after rice and wheat. Two high yielding cultivars of Indian maize (HQPM1-quality protein maize and DHM117-normal/non quality protein maize) were exposed to two levels of elevated O3 above the ambient level (NFC) viz. NFC + 15 ppb O3 (NFC + 15) and NFC + 30 ppb O3 (NFC + 30) using open top chambers under field conditions. The study was conducted to evaluate the biochemical responses of two cultivars at different developmental stages leading to change in yield responses. Initially at lower O3 dose, photosynthetic pigments showed an increase but reduction at later stage, while higher dose caused a decline at both the stages of sampling. Levels of superoxide radical (O2 (-)) and hydrogen peroxide (H2O2) significantly increased and contributed to lipid peroxidation at elevated O3. Histochemical localization assay of O2 (-) and H2O2 showed that guard cells of stomata and cells around trichomes took deeper stain at elevated O3 reflecting more formation of reactive oxygen species. Secondary metabolites like total phenol, flavonoids and anthocyanin pigments also increased in plants under O3 stress. Enzymatic antioxidants were triggered in both the cultivars due to elevated O3, while induction of non-enzymatic antioxidants was more in HQPM1. Native PAGE analysis also showed that SOD, POX, CAT, APX and GPX were stimulated at elevated O3 concentrations compared to NFC. SDS-PAGE showed reductions of major photosynthetic proteins with higher decrease in DHM117. Principal Component Analysis showed that both the cultivars showed differential response against O3 at two developmental stages. HQPM1 maintained the analogous defense strategy at both the sampling stages while DHM117 showed variable response. Overall metabolic induction of antioxidants related to defense was more in DHM117 than HQPM1. This suggests that DHM117 utilized more assimilates in maintaining the homeostasis against imposed oxidative stress, causing less translocation of assimilates to reproductive parts and thus affecting the final yield. In terms of yield it is suggested that performance of HQPM1 (quality protein maize) was better than the DHM117 (non quality protein maize).

Assessment of growth and yield losses in two Zea mays L. cultivars (quality protein maize and nonquality protein maize) under projected levels of ozone

Rapid industrialization and economic developments have increased the tropospheric ozone (O3) budget since preindustrial times, and presently, it is supposed to be a major threat to crop productivity. Maize (Zea mays L.), a C4 plant is the third most important staple crop at global level with a great deal of economic importance. The present study was conducted to evaluate the performance of two maize cultivars [HQPM1: quality protein maize (QPM)] and [DHM117: nonquality protein maize (NQPM)] to variable O3 doses. Experimental setup included filtered chambers, nonfiltered chambers (NFC), and two elevated doses of O3 viz. NFC+15 ppb O3 (NFC+15) and NFC+30 ppb O3 (NFC+30). During initial growth period, both QPM and NQPM plants showed hormetic effect that is beneficial due to exposure of low doses of a toxicant (NFC and NFC+15 ppb O3), but at later stages, growth attributes were negatively affected by O3. Growth indices showed the variable pattern of photosynthate translocation under O3 stress. Foliar injury in the form of interveinal chlorosis and reddening of leaves due to increased production of anthocyanin pigments was observed at higher concentrations of O3. One-dimensional gel electrophoresis of leaves taken from NFC+30 showed reductions of major photosynthetic proteins, and differential response was observed between the two test cultivars. Decline in the number of male flowers at elevated O3 doses suggested damaging effect of O3 on reproductive structures which might be a cause of productivity losses. Variable carbon allocation pattern particularly to husk leaves, foliar injury, and damage of photosynthetic proteins led to significant reductions in economic yield at higher O3 doses. PCA showed that both the cultivars responded more or less similarly to O3 stress in their respective groupings of growth and yield parameters, but magnitude of their response was variable. It is further supported by difference in the significance of correlations between variables of yield and AOT40. Cultivar response reflects that QPM performed better than NQPM against elevated O3.

CBFB-MYH11/RUNX1 together with a compendium of hematopoietic regulators, chromatin modifiers and basal transcription factors occupies self-renewal genes in inv(16) acute myeloid leukemia

Different mechanisms for CBFβ-MYH11 function in acute myeloid leukemia with inv(16) have been proposed such as tethering of RUNX1 outside the nucleus, interference with transcription factor complex assembly and recruitment of histone deacetylases, all resulting in transcriptional repression of RUNX1 target genes. Here, through genome-wide CBFβ-MYH11-binding site analysis and quantitative interaction proteomics, we found that CBFβ-MYH11 localizes to RUNX1 occupied promoters, where it interacts with TAL1, FLI1 and TBP-associated factors (TAFs) in the context of the hematopoietic transcription factors ERG, GATA2 and PU.1/SPI1 and the coregulators EP300 and HDAC1. Transcriptional analysis revealed that upon fusion protein knockdown, a small subset of the CBFβ-MYH11 target genes show increased expression, confirming a role in transcriptional repression. However, the majority of CBFβ-MYH11 target genes, including genes implicated in hematopoietic stem cell self-renewal such as ID1, LMO1 and JAG1, are actively transcribed and repressed upon fusion protein knockdown. Together these results suggest an essential role for CBFβ-MYH11 in regulating the expression of genes involved in maintaining a stem cell phenotype.

A survey of tuberculosis hospitals in India

SETTING

Hospitals with beds for tuberculosis (TB) in India.

OBJECTIVES

To assess diagnostic and treatment practices at institutions offering secondary or tertiary level care for TB patients, and to determine the resources being used at these institutions.

DESIGN

Countrywide cross-sectional survey of TB hospitals using a mailed semi-structured questionnaire sent to all 105 hospitals with 100 or more beds and to all State Directorate Health Services.

RESULTS

The 94 hospitals that returned the questionnaire had 15773 TB beds, one third of the total TB beds in the country. Nearly 1 million patients sought treatment in the TB hospitals and one third were diagnosed with TB; the ratio of smear-positive to smear-negative patients was 1:2.7. Sixty-four per cent of hospitals prescribed unobserved rifampicin in the continuation phase, and 56% of sputum smear-positive patients were hospitalised. The annual expenditure for the TB hospitals was more than the total annual budget for the TB control programme of the country.

CONCLUSIONS

In view of the high number of patients seen and the suboptimal practices observed, urgent steps should be taken to ensure implementation of correct diagnostic and treatment policies in hospitals with TB beds.

Effectiveness of urban community volunteers in directly observed treatment of tuberculosis patients: a field report from Haryana, North India

A tuberculosis (TB) unit covering a population of 600000 in Gurgaon District of Haryana State, India, where the DOTS-based RNTCP has been implemented since April 2000. Treatment success rate, as recorded in the TB register, of new sputum smear-positive patients receiving directly observed treatment (DOT) from community volunteers was comparable with that of patients receiving DOT from government health workers (78% vs. 77%). The proportion of patients with community volunteers increased significantly with time (13% in 2000 to 25% in 2002), even in the absence of financial incentives. In this model of community volunteer involvement in an urban TB control programme, the primary responsibility for returning late patients to treatment was with the staff of the District TB Centre.

A study of dental caries in school children from rural Haryana

The prevalence of dental caries among rural school children (688 boys and 331 girls) in the age group of 12-16 years in Haryana was found to be 39.4%. It was 37.9% in boys and 42.6% in girls. The difference between males and females was statistically not significant. A significant increase in prevalence of dental caries with age was observed (i.e. 33.1% in 12-year-old children to 45.8% in 14-year-old children). The mean DMFT per child was found to be 1.03 and DMFT per affected child was 2.6. The mean of D, M and F was found to be 1.0, 0.03 and 0.0 respectively.

Epidemiological evaluation of BCG vaccine efficacy in Delhi--1989

A field evaluation of efficacy of BCG vaccine to prevent tubercular meningitis was undertaken in a case control study in Delhi during 1988-89. Each case of tubercular meningitis was matched by age and neighbourhood with 2 controls from the community. Thirty-seven cases of tubercular meningitis were matched with 74 controls and thus 37 triplets were analysed. ODDS RATIO between BCG vaccinated and non vaccinated individuals for acquisition of tubercular meningitis was 11.3. This gives 84 per cent efficacy of BCG vaccine in the prevention of TB meningitis under the field conditions prevailing in Delhi. Paired matched analysis of tubercular meningitis with the control group 1 and 2 separately revealed the ODDS RATIO to be 9.5 and 15 respectively. The corresponding BCG vaccine efficacy worked out were 90 and 93 per cent respectively. Authors suggest that this method of evaluating BCG vaccine efficacy is fairly reliable and cost effective. This methodology could be further simplified by using hospital patients as control and be introduced to evaluate BCG vaccine efficacy in different areas with reference to its role in preventing tubercular meningitis under the programme of immunisation.

New 6-Aryl-2-pyrones from Gentiana pedicellata*

Three new 6-aryl-2-pyrones, viz. pedicellin ( 1), pedicellanin ( 2), and pedicellatin ( 3), have been isolated from the whole plant of GENTIANA PEDICELLATA W ALL., collected when in flower. The compounds have been characterized on the basis of chemical transformation and comprehensive spectral evidence. This is the first report of occurrence of 6-aryl-2-pyrones in a member of the family Gentianaceae. The other secondary metabolites, e.g. triterpene, secoiridoid, and degraded carotenoid, present in this species are typical of the GENTIANA. 1 and 2 produced significant adaptogenic and anti-stress effects in animal models thereby justifying the use of the title species in popular medicine.