Application of nanoparticles for management of plant viral pathogen: Current status and future prospects

Plant viruses are responsible for nearly 47 % of all crop losses brought by plant diseases, which have a considerable negative impact on agricultural output. Nanoparticles have the potential to greatly raise agricultural output due to their wonderful applications in the fields of highly sensitive biomolecular detection, disease diagnostics, antimicrobials, and therapeutic compounds. The application of nanotechnology in plant virology is known as nanophytovirology, and it involves biostimulation, drug transport, genetic manipulation, therapeutic agents, and induction of plant defenses. The inactivation and denaturation of capsid protein, nucleic acids (RNA or DNA), and other protein constituents are involved in the underlying mechanism. To determine the precise mechanism by which nanoparticles affect viral mobility, reproduction, encapsidation, and transmission, more research is however required. Nanoparticles can be used to precisely detect plant viruses using nanobiosensors or as biostimulants. The varieties of nanoparticles employed in plant virus control and their methods of virus suppression are highlighted in this review.

Characterization of Type1 Lipid Transfer Protein from Citrus sinensis: Unraveling its potential as an antimicrobial and insecticidal agent

Lipid Transfer Protein1 (LTP1) is a cationic, multifaceted protein belonging to the pathogenesis-related protein (PR14) family. Despite being involved in diverse physiological processes and defense mechanisms, the precise in-vivo role of LTP1 remains undiscovered. This work presents the characterization of recombinant Citrus sinensis LTP1 (CsLTP1) along with lipid binding studies through in-silico and in-vitro approaches. CsLTP1 demonstrated great thermal and pH stability with a huge biotechnological potential. It showed in-vitro binding capacity with jasmonic acid and lipids involved in regulating plant immune responses. Gene expression profiling indicated a significant upregulation of CsLTP1 in Candidatus-infected Citrus plants. CsLTP1 disrupted the cell membrane integrity of various pathogens, making it a potent antimicrobial agent. Further, in-vivo antimicrobial and insecticidal properties of CsLTP1 have been explored. The impact of exogenous CsLTP1 treatment on rice crop metabolism for managing blight disease has been studied using GC-MS. CsLTP1 triggered crucial metabolic pathways in rice plants while controlling the blight disease. CsLTP1 effectively inhibited Helicoverpa armigera larvae by impeding mid-gut α-amylase activity and obstructing its developmental stages. This study highlights the pivotal role of CsLTP1 in plant defense by offering insights for developing multi-target therapeutic agent or disease-resistant varieties to comprehensively tackle the challenges towards crop protection.

Comparative Analysis of Inhibitor Binding to Peroxiredoxins from Candidatus Liberibacter asiaticus and Its Host Citrus sinensis

The peroxiredoxins (Prxs), potential drug targets, constitute an important class of antioxidant enzymes present in both pathogen and their host. The comparative binding potential of inhibitors to Prxs from pathogen and host could be an important step in drug development against pathogens. Huanglongbing (HLB) is a most devastating disease of citrus caused by Candidatus Liberibacter asiaticus (CLa). In this study, the binding of conoidin-A (conoidin) and celastrol inhibitor molecules to peroxiredoxin of bacterioferritin comigratory protein family from CLa (CLaBCP) and its host plant peroxiredoxin from Citrus sinensis (CsPrx) was assessed. The CLaBCP has a lower specific activity than CsPrx and is efficiently inhibited by conoidin and celastrol molecules. The biophysical studies showed conformational changes and significant thermal stability of CLaBCP in the presence of inhibitor molecules as compared to CsPrx. The surface plasmon resonance (SPR) studies revealed that the conoidin and celastrol inhibitor molecules have a strong binding affinity (KD) with CLaBCP at 33.0 µM, and 18.5 µM as compared to CsPrx at 52.0 µM and 61.6 µM, respectively. The docked complexes of inhibitor molecules showed more structural stability of CLaBCP as compared to CsPrx during the run of molecular dynamics-based simulations for 100 ns. The present study suggests that the conoidin and celastrol molecules can be exploited as potential inhibitor molecules against the CLa to manage the HLB disease.

Identification and evaluation of potential inhibitor molecules against TcyA from Candidatus Liberibacter asiaticus

Of the two putative amino acid binding periplasmic receptors of ABC transporter family in Candidatus Liberibacter asiaticus (CLas), cystine binding receptor (CLasTcyA) has been shown to mainly express in phloem of citrus plant and is a target for inhibitor development. The crystal structure of CLasTcyA in complex with substrates has been reported earlier. The present work reports the identification and evaluation of potential candidates for their inhibitory potential against CLasTcyA. Among many compounds, selected through virtual screening, and MD simulation, pimozide, clidinium, sulfasalazine and folic acid showed significantly higher affinities and stability in complex with CLasTcyA. The SPR studies with CLasTcyA revealed significantly higher binding affinities for pimozide and clidinium (Kd, 2.73 nM and 70 nM, respectively) as compared to cystine (Kd, 1.26 µM). The higher binding affinities could be attributed to significantly increased number of interactions in the binding pocket as evident from the crystal structures of CLasTcyA in complex with pimozide and clidinium as compared to cystine. The CLasTcyA possess relatively large binding pocket where bulkier inhibitors fit quite well. In planta studies, carried out to assess the effect of inhibitors on HLB infected Mosambi plants, showed significant reduction in CLas titre in plants treated with inhibitors as compared to control plants. The results showed that pimozide exhibited higher efficiency as compared to clidinium in reducing CLas titre in treated plants. Our results showed that the inhibitor development against critical proteins like CLasTcyA can be an important strategy in management of HLB.

Symptoms and Prevalence of Constipation among Adult Population of Bangladesh

Background

Constipation is one of the most common gastrointestinal disorders. The prevalence of constipation is rapidly increasing globally. It has adverse effects on the patient's quality of life including productivity and results in a high financial hardship on the healthcare system. The aim of the study was to estimate the symptoms and prevalence of constipation among the adult population of Bangladesh.

Materials and methods

It was a cross-sectional observational study based on a structured questionnaire and a checklist. In this study, three criteria were used for the diagnosis of chronic constipation (self-reported perception, Rome III criteria, and Bristol's criteria). The study was conducted among 1,550 population between July 2019 and December 2019.

Result

The study population consisted of 1,550 respondents, among them 41.61% male and 58.39% female, and the mean age was 32.71 ± 9.72 years. In the study, 12.2% of the population was categorized to have constipation according to self-reported perception, 11.2% according to Rome III, and 10.3% reported to have been suffering from constipation according to Bristol chart.Female gender tends to have a greater prevalence than male. In multivariate analysis for constipation, betel nut chewer, alcohol consumer, diabetes mellitus, hypertension, GI surgery, and bronchial asthma were significantly (p < 0.001) associated with constipation. According to Bristol's criteria, the most common stool form was Type III (sausage-shaped with cracked surface) among the Bangladeshi population in this study.

Conclusion

Chronic constipation is a common problem worldwide. The findings of this study suggest that there is a high prevalence of constipation among the general population of Bangladesh. Decreasing modifiable risk factors of constipation can reduce its prevalence and burden of the disease. Bangladesh is markedly deficient in literature citing constipation prevalence and determinants. These findings may commence a call for setting priority as one of the major public health problems and demanding attention for both at the clinical and community levels.

How to cite this article

Ghosh DK, Sarkar DK, Nath M, et al. Symptoms and Prevalence of Constipation among Adult Population of Bangladesh. Euroasian J Hepato-Gastroenterol 2023;13(2):45-49.

Frequency of Defecation and Form of Stool among General Bangladeshi Population

Data on stool form and defecation frequency which are a prerequisite for defining normal bowel habit are lacking in Bangladesh. This observational cross sectional study was designed to find out defecation frequency and stool form among general population in Bangladesh. This study was performed in the Department of Gastroenterology, Shaheed Suhrawardy Medical College Hospital, Dhaka, Bangladesh from July 2017 to June 2018. Apparently healthy 1090 respondents were evaluated for predominant stool form (Bristol chart) and frequency. Data on demographic and life-style were collected. The study population consisted of 1090 respondents, among them, 65.13% male and 34.87% female and mean age of them was 40.20±12.39 years. Most of the people 874(80.2%) passed stool between 12-14 times per week followed by 111(10.2%) less than 3 stools per week, 95(8.7%) passed more than 14 stools per week and 10(0.9%) between 3-12 stools per week, p<0.001. Most people passed predominantly Bristol type IV stool- 610(56.0%); followed by type III- 274(25.1%). Other stool forms were: type I- 52(4.8%), type II- 59(5.4%), type V- 31(2.8%), type VI- 33(3.0%), type VII- 31(2.8%), p<0.001. In regard to the physical activity, most of the respondents (70.0%) are physically active whereas about 13.0% are sedentary and about 17.0% are physically intermediate between the two, p<0.001. In the case of dietary habit, most of the participants are non-vegetarian (82.5%) and the remaining are vegetarian (11.1%) and occasional non vegetarian (6.4%), p<0.001. Median stool frequency in the studied population was 14 per week and predominant form was Bristol type IV. Older age was associated with lesser stool frequency, particularly among female subjects.

Characterization of a cytoplasmic 2-Cys peroxiredoxin from Citrus sinensis and its potential role in protection from oxidative damage and wound healing

In present work, the recombinant cytoplasmic 2-Cys peroxiredoxin from Citrus sinensis (CsPrx) was purified and characterized. The peroxidase activity was examined with different substrates using DTT, a non-physiological electron donor. The conformational studies, in oxidized and reduced states, were performed using circular dichroism (CD) and fluorescence measurement. The CD analysis showed higher α-helical content for reduced state of the protein. The thermal stability studies of CsPrx by Differential Scanning Calorimetry (DSC) showed that oxidized state is more stable as compared to the reduced state of CsPrx. In vitro studies showed that the CsPrx provides a protective shield against ROS and free radicals that participate in the degradation of plasmid DNA. The pre-treatment of 10 μM CsPrx provide almost 100% protection against peroxide-mediated cell killing in the Vero cells. CsPrx showed significant cell proliferation and wound healing properties. The superior morphology of viable cells and wound closure was found at 20 μM CsPrx treated for 12 h. The results demonstrated that CsPrx is a multifaceted protein with a significant role in cell proliferation, wound healing and protection against hydrogen peroxide-induced cellular damage. This could be the first report of a plant peroxiredoxin being characterized for biomedical applications.

A Comprehensive Analysis of Citrus Tristeza Variants of Bhutan and Across the World

Mandarin orange is economically one of the most important fruit crops in Bhutan. However, in recent years, orange productivity has dropped due to severe infection of citrus tristeza virus (CTV) associated with the gradual decline of citrus orchards. Although the disease incidence has been reported, very limited information is available on genetic variability among the Bhutanese CTV variants. This study used reverse transcription PCR (RT-PCR) to detect CTV in collected field samples and recorded disease incidence up to 71.11% in Bhutan’s prominent citrus-growing regions. To elucidate the extent of genetic variabilities among the Bhutanese CTV variants, we targeted four independent genomic regions (5′ORF1a, p25, p23, and p18) and analyzed a total of 64 collected isolates. These genomic regions were amplified and sequenced for further comparative bioinformatics analysis. Comprehensive phylogenetic reconstructions of the GenBank deposited sequences, including the corresponding genomic locations from 53 whole-genome sequences, revealed unexpected and rich diversity among Bhutanese CTV variants. A resistant-breaking (RB) variant was also identified for the first time from the Asian subcontinent. Our analyses unambiguously identified five (T36, T3, T68, VT, and HA16-5) major, well-recognized CTV strains. Bhutanese CTV variants form two additional newly identified distinct clades with higher confidence, B1 and B2, named after Bhutan. The origin of each of these nine clades can be traced back to their root in the north-eastern region of India and Bhutan. Together, our study established a definitive framework for categorizing global CTV variants into their distinctive clades and provided novel insights into multiple genomic region-based genetic diversity assessments, including their pathogenicity status.

Development of a SYBR Green-based RT-qPCR assay for the detection of Indian citrus ringspot virus

The Indian citrus ringspot virus (ICRSV) that causes ringspot disease, especially to 'Kinnow mandarin' hampers the sustainability of crop production. Presently, the disease is not amenable for control through host resistance or the introduction of chemicals, hence raising virus-free plants is one of the most effective approaches to manage the disease. Consequently, it is necessary to develop rapid, sensitive, specific, and early diagnostic methods for disease control. In the present study, newly designed primers targeting a 164 bp region of the ICRSV coat protein gene were used to develop and optimize a SYBR Green-based quantitative reverse transcription polymerase chain reaction (RT-qPCR) assay, for the detection of ICRSV. The RT-qPCR assay was evaluated and confirmed using viral RNA extracted from ICRSV infected plants maintained in screen house as well as field samples. The standard curves displayed a dynamic linear range across eight log units of ICRSV-cRNA copy number ranging from 9.48.1 fmol (5.709 × 10⁹) to 0.000948 amol (5.709 × 10²), with detection limit of 5.709 × 10² copies per reaction using serial tenfold diluted in vitro transcribed viral cRNA. The developed RT-qPCR is very specific to ICRSV does not react to other citrus pathogens, and approximately 100-fold more sensitive than conventional RT-PCR. Thus, this assay will be useful in laboratories, KVKs, and nurseries for the citrus budwood certification program as well as in plant quarantine stations. To our knowledge, this is the first study of the successful detection of ICRSV by RT-qPCR.

Pairwise Balanced Designs From Cyclic PBIB Designs

A pairwise balanced designs was constructed using cyclic partially balanced incomplete block designs with either (λ1 – λ2) = 1 or (λ2 – λ1) = 1. This method of construction of Pairwise balanced designs is further generalized to construct it using cyclic partially balanced incomplete block design when |(λ1 – λ2)| = p. The methods of construction of pairwise balanced designs was supported with examples. A table consisting parameters of Cyclic PBIB designs and its corresponding constructed pairwise balanced design is also included.

In-silico screening and identification of potential inhibitors against 2Cys peroxiredoxin of Candidatus Liberibacter asiaticus

Huanglongbing (HLB) is a worldwide citrus plant disease-related to non-culturable and fastidious α-proteobacteria Candidatus Liberibacter asiaticus (CLas). In CLas, Peroxiredoxin (Prx) plays a major role in the reduction of the level of reactive species such as reactive oxygen species (ROS), free radicals and peroxides, etc. Here, we have used structure-based drug designing approach was used to screen and identify the potent molecules against 2Cys Prx. The virtual screening of fragments library was performed against the three-dimensional validated model of Prx. To evaluate the binding affinity, the top four molecules (N-Boc-2-amino isobutyric acid (B2AI), BOC-L-Valine (BLV), 1-(boc-amino) cyclobutane carboxylic acid (1BAC), and N-Benzoyl-DL-alanine (BDLA)) were docked at the active site of Prx. The molecular docking results revealed that all the identified molecules had a higher binding affinity than Tert butyl hydroperoxide (TBHP), a substrate of Prx. Molecular dynamics analysis such as RMSD, Rg, SASA, hydrogen bonds, and PCA results indicated that Prx-inhibitor(s) complexes had lesser fluctuations and were more stable and compact than Prx-TBHP complex. MMPBSA results confirmed that the identified compounds could bind at the active site of Prx to form a lower energy Prx-inhibitor(s) complex than Prx-TBHP complex. The identified potent molecules may pave the path for the development of antimicrobial agents against CLA.Communicated by Ramaswamy H. Sarma.

A Rapid and Sensitive Reverse Transcription-Loop-Mediated Isothermal Amplification (RT-LAMP) Assay for the Detection of Indian Citrus Ringspot Virus

Indian citrus ringspot virus (ICRSV) is a devastating pathogen that has a particularly deleterious effect on the 'Kinnow mandarin', a commercial citrus crop cultivated in the northwest of India. ICRSV belongs to the Mandarivirus genus within the family of Alphaflexiviridae and has a positive sense single-stranded RNA (ssRNA) genome consisting of six open reading frames (ORFs). Severe cases of ICRSV result in a significant reduction in both the yield and quality of crops. Consequently, there is an urgent need to develop methods to detect ICRSV in an accurate and timely manner. Current methods involve a two-step reverse transcription polymerase chain reaction (RT-PCR) that is time consuming. Here, we describe a novel, one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) method for the sensitive and rapid detection of ICRSV. To standardize the RT-LAMP assay, four different primers were designed and tested to target the coat protein gene of ICRSV. Amplification results were visualized by a color change after addition of SYBR Green I. The standardized RT-LAMP assay was highly specific and successfully detected all 35 ICRSV isolates tested from the Punjab and Haryana states of India. Furthermore, there was no cross-reaction with 17 isolates of five other citrus pathogens that are common in India. The ICRSV RT-LAMP assay developed in the present study is a simple, rapid, sensitive, specific technique. Moreover, the assay consists of only a single step and is more cost effective than existing methods. This is the first application of RT-LAMP for the detection of ICRSV. Our RT-LAMP assay is a powerful tool for the detection of ICRSV and will be particularly useful for large-scale indexing of field samples in diagnostic laboratories, in nurseries, and for quarantine applications.

Detection and Molecular Characterization of 'Candidatus Liberibacter asiaticus' and Citrus Tristeza Virus Associated with Citrus Decline in Bhutan

Citrus, mainly mandarin (Citrus reticulata Blanco), is an economically important fruit crop in Bhutan. Despite having favorable agroclimatic conditions for citrus cultivation, the early decline of fruit-bearing orchards coupled with low crop productivity is a major concern among citrus growers. During a recent survey, an association of 'Candidatus Liberibacter asiaticus' (citrus greening) and citrus tristeza virus (CTV), either singly or as mixed infections in declined citrus trees, was recorded in all four major citrus-growing districts (Tsirang, Dagana, Zhemgang, and Sarpang). Using PCR-based diagnosis, a higher incidence of citrus greening (27.45%) and tristeza (70.58%) was observed in symptomatic field samples. Detection and characterization of 'Ca. L. asiaticus' was performed based on the 16S ribosomal DNA, prophage gene, 50S ribosomal rplA-rplJ gene, and tandem repeats of the CLIBASIA_01645 locus. Similarly, the coat protein, p23, and p18 genes were used as genetic markers for the detection and characterization of Bhutanese CTV. The 'Ca. L. asiaticus' isolates from Bhutan segregated into classes II and III based on the CLIBASIA_01645 locus, analogous to Indian isolates from the northeast region and Term-A based on the CLIBASIA_05610 locus. CTV isolates of Bhutan were observed as closely related to the VT strain, which is considered to be the most devastating. To the best of our knowledge, this is the first study on molecular characterization of 'Ca. L. asiaticus' and CTV isolates and their association with citrus decline in Bhutan.

Sub-TeV H^{+} Boson Production as Probe of Extra Top Yukawa Couplings

We suggest searching for the charged Higgs boson at the Large Hadron Collider (LHC) via cg→bH^{+}→btb[over ¯]. In the general two Higgs doublet model, extra top Yukawa couplings ρ_{tc} and ρ_{tt} can drive the disappearance of antimatter from the Universe, while c[over ¯]bH^{+} and t[over ¯]bH^{+} couple with strength ρ_{tc}V_{tb} and ρ_{tt}V_{tb}, respectively. For ρ_{tc},ρ_{tt}∼0.5, and m_{H^{+}}∼300-500  GeV, evidence could emerge from LHC run 2 data at hand and discovery by adding run 3 data in the near future.

In-silico characterization and RNA-binding protein based polyclonal antibodies production for detection of citrus tristeza virus

Citrus tristeza virus (CTV) is the etiologic agent of the destructive Tristeza disease, a massive impediment for the healthy citrus industry worldwide. Routine indexing of CTV is an essential component for disease surveys and citrus budwood certification for production of disease-free planting material. Therefore, the present study was carried out to develop an efficient serological assay for CTV detection based on the RNA binding protein (CTV-p23), which is translated from a subgenomic RNA (sgRNA) that accumulates at higher levels in CTV-infected plants. CTV-p23 gene was amplified, cloned and polyclonal antibodies were raised against recombinant CTV-p23 protein. The efficacy of the produced polyclonal antibodies was tested by Western blots and ELISA to develop a quick, sensitive and economically affordable CTV detection tool and was used for indexing of large number of plant samples. The evaluation results indicated that the developed CTV-p23 antibodies had an excellent diagnostic agreement with RT-PCR and would be effective for the detection of CTV in field samples. Furthermore, CTV-p23 gene specific primers designed in the present study were found 1000 times more sensitive than the reported coat protein (CTV-p25) gene specific primers for routine CTV diagnosis. In silico characterizations of CTV-p23 protein revealed the presence of key conserved amino acid residues that involved in the regulation of protein stability, suppressor activity and protein expression levels. This would provide precious ground information towards understanding the viral pathogenecity and protein level accumulation for early diagnosis of virus.

Molecular detection, identification, and sequence analysis of 'Candidatus Liberibacter asiaticus' associated with Huanglongbing disease of citrus in North India

Huanglongbing (HLB, Citrus greening), caused by a phloem-limited fastidious gram-negative bacterium, "Candidatus Liberibacter spp.", is one of the devastating diseases of citrus worldwide. The pathogen belongs to the alpha-proteobacteria group and is classified on the basis of its geographical origin and 16S rRNA sequence diversity. Although the disease has been reported from all citrus growing states of India, the status and the molecular variability among the isolates from the Northern part of the country is unknown. A total of five different HLB isolates originating from Northern India showing variable symptoms were studied. The genomic regions of four different genes, i.e., 16S rRNA, intergenic 16S/23S rRNA spacer region, rplA-rplJ, and CLIBASIA_01645 were amplified by PCR, sequenced, and variations in these sequences were assessed. Analysis of 16S rRNA clearly indicated that all five isolates fit in to 'Candidatus Liberibacter asiaticus' (CLas) group. However, 16S/23S rRNA intergenic spacer region-based analysis failed to segregate these isolates beyond species level. Sequence analysis of rplA-rplJ gene and CLIBASIA_01645 loci also confirmed the existence of diversity among the 'CLas' in the surveyed areas. Further, 16S rRNA and rplA-rplJ-based SNP analysis revealed that some isolates segregated into three new lineages, two on the basis of 16Sr (16Sr-XV and 16Sr-XVI), and one based on β-rp (rp-IV), respectively. A tandem repeat number (TRN) at CLIBASIA_01645 region were TRN = 5, 6 and 13; with TRN = 6 being common in three 'CLas' isolates. Overall, the study demonstrated that all examined five HLB isolates belonged to 'CLas' group. However, these isolates showed distinct sequence variability in three out of four genomic regions. The results provide a robust framework for understanding differences in pathogenicity among different HLB isolates as it is plausibly related to their genomic variation, and evolutionary history.

Characterization of the heavy metal binding properties of periplasmic metal uptake protein CLas-ZnuA2

Candidatus Liberibacter asiaticus (CLas), a phloem-limited unculturable Gram-negative bacterium, causes citrus greening disease.

Crystal structures of a putative periplasmic cystine-binding protein from Candidatus Liberibacter asiaticus: insights into an adapted mechanism of ligand binding

The amino acid-binding receptors, a component of ABC transporters, have evolved to cater to different specificities and functions. Of particular interest are cystine-binding receptors, which have shown broad specificity. In the present study, a putative periplasmic cystine-binding protein from Candidatus Liberibacter asiaticus (CLasTcyA) was characterized. Analysis of the CLasTcyA sequence and crystal structures in the ligand-bound state revealed novel features of CLasTcyA in comparison to related proteins. One of the unique features found in CLasTcyA structure was the positioning of the C-terminal extended loop of one chain very close to the substrate-binding site of the adjacent monomer in the asymmetric unit. The presence of a disulphide bond, unique to Candidatus Liberibacter family, holds the C-terminal extended loop in position. Analysis of the substrate-binding pocket of CLasTcyA suggested a broad specificity and a completely different orientation of the bound substrates in comparison to related protein structures. The open conformation for one of the two chains of the asymmetric unit in the Arg-bound structure revealed a limited open state (18.4°) for CLasTcyA as compared to open state of other related proteins (~ 60°). The strong interaction between Asp126 on helix-α5 of small domain and Arg82 (bigger domain) restricts the degree of opening in ligand-free open state. The dissociation constant of 1.26 μm by SPR and 3.7 μm by MST exhibited low affinity for the cystine. This is the first structural characterization of an l-cystine ABC transporter from plant pathogen and our results suggest that CLasTcyA may have evolved to cater to its specific needs for its survival in the host.

Development of a recombinase polymerase based isothermal amplification combined with lateral flow assay (HLB-RPA-LFA) for rapid detection of "Candidatus Liberibacter asiaticus"

Huanglongbing (HLB) or citrus greening is highly destructive disease that is affecting the citrus industry worldwide and it has killed millions of citrus plants globally. HLB is caused by the phloem limited, Gram negative, non-culturable, alpha-proteobacterium, 'Candidatus Liberibacter asiaticus'. Currently, polymerase chain reaction (PCR) and real time PCR have been the gold standard techniques used for detection of 'Ca. L. asiaticus'. These diagnostic methods are expensive, require well equipped laboratories, not user-friendly and not suitable for on-site detection of the pathogen. In this study, a sensitive, reliable, quick and low cost recombinase polymerase based isothermal amplification combined with lateral flow assay (HLB-RPA-LFA) technique has been developed as a diagnostic tool for detection of 'Ca. L. asiaticus'. The assay was standardized by designing the specific primer pair and probe based on the conserved 16S rRNA gene of 'Ca. L. asiaticus'. The assay was optimized for temperature and reaction time by using purified DNA and crude plant extracts and the best HLB-RPA-LFA was achieved at the isothermal temperature of 38°C for 20 to 30 min. The efficacy and sensitivity of the assay was carried out by using field grown, HLB-infected, HLB-doubtful and healthy citrus cultivars including mandarin, sweet orange cv. mosambi, and acid lime. The HLB-RPA-LFA did not show cross-reactivity with other citrus pathogens and is simple, cost-effective, rapid, user-friendly and sensitive. Thus, the HLB-RPA-LFA method has great potential to provide an improved diagnostic tool for detection of 'Ca. L. asiaticus' for the farmers, nurserymen, disease surveyors, mobile plant pathology laboratories, bud-wood certification and quarantine programs.

Antimicrobial nano-zinc oxide-2S albumin protein formulation significantly inhibits growth of "Candidatus Liberibacter asiaticus" in planta

Huanglongbing (HLB, also known as citrus greening) is considered to be the most devastating disease that has significantly damaged the citrus industry globally. HLB is caused by the Candidatus Liberibacter asiaticus (CLas), the fastidious phloem-restricted gram-negative bacterium, vectored by the asian citrus psyllid. To date, there is no effective control available against CLas. To alleviate the effects of HLB on the industry and protect citrus farmers, there is an urgent need to identify or develop inhibitor molecules to suppress or eradicate CLas from infected citrus plant. In this paper, we demonstrate for the first time an in planta efficacy of two antimicrobial compounds against CLas viz. 2S albumin (a plant based protein; ~12.5 kDa), Nano-Zinc Oxide (Nano-ZnO; ~ 4.0 nm diameter) and their combinations. Aqueous formulations of these compounds were trunk-injected to HLB affected Mosambi plants (Citrus sinensis) grafted on 3-year old rough lemon (C. jambhiri) rootstock with known CLas titer maintained inside an insect-free screen house. The effective concentration of 2S albumin (330 ppm) coupled with the Nano-ZnO (330 ppm) at 1:1 ratio was used. The dynamics of CLas pathogen load of treated Mosambi plants was assessed using TaqMan-qPCR assay every 30 days after treatment (DAT) and monitored till 120 days. We observed that 2S albumin-Nano-ZnO formulation performed the best among all the treatments decreasing CLas population by 96.2%, 97.6%, 95.6%, and 97% of the initial bacterial load (per 12.5 ng of genomic DNA) at 30, 60, 90, and 120 DAT, respectively. Our studies demonstrated the potency of 2S albumin-Nano-ZnO formulation as an antimicrobial treatment for suppressing CLas in planta and could potentially be developed as a novel anti CLas therapeutics to mitigate the HLB severity affecting the citrus industry worldwide.

Quantitative distribution of Citrus yellow mosaic badnavirus in sweet orange (Citrus sinensis) and its implication in developing disease diagnostics

Citrus yellow mosaic badnavirus (CMBV) is the etiologic agent of citrus yellow mosaic disease, which has caused serious economic losses to Indian citrus industry. CMBV is a quarantined pathogen that is geographically restricted to India. To prevent unintentional movement of the virus to other major citrus-growing countries in fruits, root stocks or grafted citrus plants and facilitate trade, a sensitive, validated diagnostic tool is needed. In the present study, we developed a SYBR Green real-time PCR-based method to detect and quantify CMBV in different tissues of infected Mosambi sweet orange (Citrus sinensis) and compared its sensitivity to conventional PCR protocols. Primers were designed to recognize a portion of the CMBV capsid protein gene. Conventional and real-time PCR were performed on several different tissues: shoot tips, leaves displaying typical CMBV symptoms, asymptomatic leaves, senescent leaves, thorns, green stems and feeder roots. The detection limit of CMBV by conventional PCR was 2.5 × 10⁴ copies per 5 ng of total genomic DNA, while the detection limit of real-time PCR was found to be 4.6 × 10² virus copies per 5 ng of viral DNA. The viral load varied between different tissues. The highest concentration occurred in feeder roots (3.5 × 10⁸ copies per 5 ng of total genomic DNA) and the lowest in thorns (1 × 10⁶ copies per 5 ng of total genomic DNA). The variation in viral load within different tissues suggests movement of the virus within an infected plant that follows the path of photo-assimilates via the phloem. In symptomatic leaves, the CMBV concentration was highest in the lamella followed by midrib and petiole, suggesting that virus resides inside these sections of a leaf and side by side symptoms develop. On the other hand, in asymptomatic leaves, the petiole contained higher virus load than the lamella and midrib suggesting that the pathogen gets established from the stem through the phloem into petiole then infects the lamella and midrib. In addition to information on virus movement, the distribution of CMBV in different tissues helps with the selection of tissues with relatively higher viral load to sample for early and sensitive diagnosis of the disease, which will be useful for better management of the disease in endemic areas.

Characterization of a bacterioferritin comigratory protein family 1-Cys peroxiredoxin from Candidatus Liberibacter asiaticus

To defend against the lethality of the reactive oxygen species (ROS), nature has armed microorganisms with a range of antioxidant proteins. These include peroxiredoxin (Prx) super family proteins which are ubiquitous cysteine-based non-heme peroxidases. The phytopathogenic bacterium Candidatus Liberibacter asiaticus (CLA), an etiological agent of citrus plants diseases, posses many genes for defense against oxidative stress. The bacterioferritin comigratory protein (BCP), a member of Prxs, is part of an oxidative stress defense system of CLA. The key residue of these enzymes is peroxidatic Cys (termed C_PSH) which is contained within an absolutely conserved PXXX (T/S) XXC motif. In the present study, a 1-Cys Prx enzyme (CLa-BCP), having C_PSH/sulfenic acid cysteine (C-46) but lacking the resolving cysteine (C_RSH), was characterized from CLA. The peroxidase activity was demonstrated using a non-physiological electron donor DTT against varied substrates. The protein was shown to have the defensive role against peroxide-mediated cell killing and an antioxidant activity. In vitro DNA-binding studies showed that this protein can protect supercoiled DNA from oxidative damage. To the best of our knowledge, this is the first report on a 1-Cys BCPs to have an intracellular reactive oxygen species scavenging activity.

Association between Helicobacter Pylori and Hyperemesis Gravidarum

Background: Hyperemesis gravidarum (HG) is the severe form of the nausea & vomiting in pregnancy and is associated with weight loss, ketonemia ,ketonuria ,electrolyte imbalances and profound volume depletion. Increased accumulation of fluid caused by elevated steroid hormones in pregnancy, a shift in pH and change of pH in the gastrointestinal tract could result in the manifestation of subclinical Helicobacter pylori (H. Pylori) infection. We therefore examined whether seropositivity for IgG antibodies to H. Pylori may be related to hyperemesis graviderum.Objective: To determine the association of H-pylori infection in hyperemesis graviderum patients.Methodology: A cross sectional study was conducted in the department of obstetrics and gynaecology, Dhaka medical college hospital from January 2007 to December 2008. Total 82 pregnant patients, 40 were hyperemesis gravidarum patients (Cases, group A) and 42 were normal pregnancy without hyperemesis graviderum (Control, group B) for admission and attending for routine ANC in OPD were selected. Purposive sampling method was followed as per inclusion and exclusion criteria. Evaluation of the patients was based on history, physical examination and investigation. Serum IgG antibody response to H.pylori antigen by ELISA were measured from every patients and analysed for its association with HG.Results: Most of the patients of this study were primi gravida, Group-A was 72.5% and Group-B was 66.7%. Maximum number of women in both the groups belonged to lower socio-economic status (Group-A was 85% and Group-B was (76%). Previous H/O hyperemesis gravidarum in the Group-A was 52.5% and Group-B was 07 % (p<.01), that is statistically highly significant. Antibody to Helicobactor pylori in serum was positive in Group-A 47.5%, and Group-B 19%. The difference was statistically significant. (p value-0.006).Conclusion: According to the findings of our study, H.pylori infection would seem to be an important associated factor in the exacerbation of HG, but it does not seem to be the only cause of the disease.J Shaheed Suhrawardy Med Coll, June 2016, Vol.8(1); 13-16

Crystal structure analysis in Zn2+-bound state and biophysical characterization of CLas-ZnuA2

A periplasmic solute binding protein from second of the two gene clusters of Znu system in CLA (CLas-ZnuA2) belong to Cluster A1 family of solute binding proteins (SBPs). The crystal structures in metal-free, intermediate and metal-bound states, in the previous study, revealed the unusual mechanism of metal binding and release for CLas-ZnuA2. Although CLas-ZnuA2 showed maximum sequence identity to the Mn/Fe-specific SBPs, the mechanistic resemblance seems to be closer to Zn-specific SBPs of Cluster A-I family. The present study reports the binding affinity studies using SPR and CD and crystal structure of CLas-ZnuA2 in Zn²⁺-bound state. Despite a similar overall structure, there are noticeable differences at the metal binding site. The SPR and CD analysis confirmed our previous observation that CLas-ZnuA2 exhibits a low metal-binding affinity. The low metal-binding affinity of CLas-ZnuA2 could be attributed to the presence of a proline in linker helix resulting in relatively higher bending and rigidity of the same. This structural feature fixes the C-domain similar to metal-bound states of related SBPs. Further, the binding of both Mn²⁺ and Zn²⁺ occurs pentavalently with square pyramidal geometry not preferred by either. The site-specific positive Darwinian selection analysis showed that the proline in linker helix is under purifying selection and might have diverged long ago. Our structural and evolutionary analyses suggest that CLasZnua2 might have evolved, particularly for plant pathogens, to facilitate transport of both Mn²⁺ and Zn²⁺, with reversible binding to Zn²⁺, unlike other Mn-binding SBPs (PsaA).

Genetic Diversity of the Indian Populations of 'Candidatus Liberibacter asiaticus' Based on the Tandem Repeat Variability in a Genomic Locus

Citrus huanglongbing (HLB, citrus greening disease) is an extremely destructive disease affecting citrus and causes severe economic loss to the crop yield worldwide. The disease is caused by a phloem-limited, noncultured, gram-negative bacteria Candidatus Liberibacter spp., the widely present and most destructive species being 'Candidatus Liberibacter asiaticus'. Although the disease has been reported from almost all citrus growing regions of India, knowledge on the molecular variability of the pathogen 'Ca. L. asiaticus' populations from different geographical regions and cultivars is limited. In the present study, variability of the Indian 'Ca. L. asiaticus' based on the tandem repeats at the genomic locus CLIBASIA_01645 was characterized and categorized into four classes based on the tandem repeat number (TRN); Class I (TRN≤5), Class II (TRN>5≤10), Class III (TRN>10≤15), and Class IV (TRN>15). The study revealed that the Indian population of 'Ca. L. asiaticus' is more diverse than reported for Florida and Guangdong populations, which showed less diversity. While Florida and Guangdong populations were dominated by a TRN5 and TRN7 genotype, respectively, the Indian 'Ca. L. asiaticus' populations with TRN copy numbers 9, 10, 11, 12, and 13 were widely distributed throughout the country. Additionally, TRN2 and TRN17 genotypes were also observed among the Indian 'Ca. L. asiaticus' populations. The predominant 'Ca. L. asiaticus' genotypes from the northeastern region of India were TRN6 and TRN7 (53.12%) and surprisingly similar to neighboring South China populations. Preliminary results showed absence of preference of citrus cultivars to any specific 'Ca. L. asiaticus' genotype.

Crystal structure of a periplasmic solute binding protein in metal-free, intermediate and metal-bound states from Candidatus Liberibacter asiaticus

The Znu system, a member of ABC transporter family, is critical for survival and pathogenesis of Candidatus Liberibacter asiaticus (CLA). Two homologues of this system have been identified in CLA. Here, we report high resolution crystal structure of a periplasmic solute binding protein from second of the two gene clusters of Znu system in CLA (CLas-ZnuA2) in metal-free, intermediate and metal-bound states. CLas-ZnuA2 showed maximum sequence identity to the Mn/Fe-specific solute binding proteins (SBPs) of cluster A-I family. The overall fold of CLas-ZnuA2 is similar to the related cluster A-I family SBPs. The sequence and structure analysis revealed the unique features of CLas-ZnuA2. The comparison of CLas-ZnuA2 structure in three states showed that metal binding and release is facilitated by a large displacement along with a change in orientation of the side chain for one of the metal binding residue (His39) flipped away from metal binding site in metal-free form. The crystal structure captured in intermediate state of metal binding revealed the changes in conformation and interaction of the loop hosting His39 during the metal binding. A rigid body movement of C-domain along with partial unfolding of linker helix at its C-terminal during metal binding, as reported for PsaA, was not observed in CLas-ZnuA2. The present results suggest that despite showing maximum sequence identity to the Mn/Fe-specific SBPs, the mechanistic resemblance of CLas-ZnuA2 seems to be closer to Zn-specific SBPs of cluster A-I family.

Epidemiological Study on Bronchial Asthma at Shaheed Suhrawardy Medical College Hospital, Dhaka

Background: In Bangladesh more than 100 million people are suffering from cough and shortness of breath. Still people are getting unplanned treatment and taking unscientific, indigenous and sometimes harmful products to get relief.Objective: The present study was conducted to estimate the prevalence of different types of bronchial asthma in Shaheed Suhrawardy Medical College Hospital.Methodology: One hundred patients from respiratory medicine out patient department were included in this study using a well designed questionnaire, clinical examination by physician which was carried out from January, 2012 to June, 2012. The key questions were related to the type of asthma, family history, presence of atopic dermatitis and diabetes, information on smoking and alcoholic habits, domestic cooking fuel used, dwelling area, age, religion, socioeconomic status and age of onset of disease.Result: Out of 100 subjects surveyed, 42 were females and 58 were males. The type of asthma is distributed as cough-variant-asthma (8%), intermittent asthma (52%), persistent asthma (16%), seasonal asthma (22%) and occupational asthma (2%). Regarding family history, 26% showed genetic predisposition irrespective of sex. Among asthmatics, 6% were having atopic dermatitis. Forty percent were smokers, 5% were alcoholics and 28% were with diabetics. Advancing age, usual residence in urban area and lower socio-economic status were associated with significantly higher odds of having asthma.Conclusion: It showed that cough- variant-asthma, diabetes and smoking habit increase the incidence of asthma attacks.DOI: http://dx.doi.org/10.3329/jssmc.v5i2.20759J Shaheed Suhrawardy Med Coll, 2013;5(2):77-80

Diagnosis of Growing Pain in Bangladeshi Pediatric Population

Background: Unexplained limb pain is a major diagnostic challenge. Parents become very much worried as their physician are not sure regarding accurate diagnosis of unexplained limb pain. Majority of the limb pain are due to Growing pain which can be diagnosed by using Standard Criteria. Objectives: The purpose of the present study was to see the clinical aspects of growing pain and to determine the causes of unexplained limb pain. Methodology: This study prospectively examined the presence of growing pain in a self reported population of children with limb pain of unexplained etiology attending National Center for Control of Rheumatic Fever and Heart Disease over the period of 6 months. Results: Total 57 children of 3-12 yrs of age were enrolled in this study and out of them 43(75.4%) were diagnosed as Growing Pain. Mean age of growing pain was 7.77(2.66). 19 children (44.2%) were male and 24 (55.8%) were female. Most frequent site of pain was calf (65.1%) and 95% cases pain occur at night. Growing Pain usually occur at slow growing period (86%) than rapid growing period (14%). Conclusion: Majority of unexplained limb pain are growing pain which is benign. DOI: http://dx.doi.org/10.3329/jssmc.v5i1.16251 J Shaheed Suhrawardy Med Coll, 2013;5(1):46-48