Biology subjects

Zaman, R.

Publications and source records attributed to Zaman, R..

7 recordsLinked to original sources

bioRxiv2026

Integrated phytohormone quantification and metabolomics analysis enables new insights into the soil phytohormonome

The contribution of soil chemistry to plant growth and resilience, including presence of phytohormones, is increasingly recognized, yet characterization is limited by chemical complexity of soil matrices, diversity and low-abundance of metabolites. To enable further discoveries, we developed and characterized performance of a liquid chromatography-mass spectrometry method with solid phase extraction, integrating targeted and untargeted hormonomic approaches for comprehensive soil phytohormone profiling. Method performance was evaluated for fifteen plant growth-regulating compounds and precursors, including abscisic, gibberellic, jasmonic, and salicylic acids, auxins, cytokinins, karrikins, melatonin, and tryptophan, showing strong linearity (R{superscript 2} = 0.989-0.999), sensitivity (limits of detection and quantification 0.1-50.2 and 1.4-167.3 pg on-column, respectively), and precision (1.3-9.6% intraday; 3.4-34.8% interday). Soil composition impacted recovery; however, for most phytohormones rates were within 20% of matrix-adjusted spiked value, showing robustness across sandy, peat-rich, and clay-rich textures and suitable for use. We used the method to quantify analytes in research-relevant, active soils. Integration of untargeted analysis expanded coverage to 250 additional putative phytohormones and related metabolites, revealing chemical signatures potentially associated with plant community composition. This approach provides a versatile framework for investigating belowground phytohormone dynamics and their roles in plant physiology, resilience, and soil-plant feedbacks.

plant biology↗

bioRxiv2024

Assessing the Incidence and Severity of Field Diseases in Marigold (Tagetes erecta) Cultivation: Results from Jashore District, Bangladesh

A research investigation was carried out in the Jashore district of Bangladesh to study diseases affecting marigold plants, while the laboratory analyses were conducted in the Plant Disease Study Facility, Sher-e-Bangla Agricultural University, Dhaka. The experiment was conducted by surveying three farmers from each of the sixteen villages across four unions in Jhikargacha Upazila to document the occurrence and severity of diseases under natural field conditions. The fungal pathogens surveyed in these diseases were six: leaf spot, botrytis blight, flower bud rot, stem rot, foliage blight, white mold-soil-borne diseases. The most important microflora reported to be associated with these diseases include Alternaria alternata, Botrytis cinerea, Alternaria dianthi, Fusarium oxysporum, Curvularia lunata, and Sclerotinia sclerotiorum. Of these, major diseases included leaf spot, botrytis blight, foliage blight or flower and leaf blight, and flower bud rot, while minor diseases included stem rot and white mold. Disease incidence ranged from 0-54.33%, while disease severity varied from 1-24%. The paper is the first record of marigold pathogens in Bangladesh and will be highly useful during disease identification, and it would lead to the better cultivation of marigolds in this area.

plant biology↗

bioRxiv2022

ARHGAP18-Ezrin functions as a RhoA autoregulatory module in the organization of apical microvilli

The location of different actin-based structures is largely regulated by Rho GTPases through specific effectors. We use the apical aspect of epithelial cells as a model system to investigate how RhoA is locally regulated to contribute to two distinct adjacent actin-based structures. Assembly of the non-muscle myosin-2 filaments in the terminal web is dependent on RhoA activity, and assembly of the microvilli also requires active RhoA for phosphorylation and activation of ezrin. We show the RhoGAP, ARHGAP18, is localized by binding active microvillar ezrin, and this interaction enhances ARHGAP18s RhoGAP activity. We present a model where ezrin-ARHGAP18 acts as a negative autoregulatory module to locally reduce RhoA activity in microvilli. Consistent with this model, loss of ARHGAP18 results in disruption of the distinction between microvilli and the terminal web including aberrant assembly of myosin-2 filaments forming inside microvilli. Thus, ARHGAP18, through its recruitment and activation by ezrin, fine-tunes the local level of RhoA to allow for the appropriate distribution of actin-based structures between the microvilli and terminal web. As RhoGAPs vastly out-number Rho GTPases, this may represent a general mechanism whereby individual Rho effectors drive specific actin-based structures.

cell biology↗

bioRxiv2022

Bacterial communities associated with the surfaces of the fresh fruits sold around Dhaka Medical College and Hospital and their anti-microbial profiles

BackgroundNow-a-days, fresh fruits are popular sources of healthy diets with low energy density. Since they are consumed raw, it may act as a source of foodborne disease and a reservoir for antibiotic resistant organisms. This study aimed to determine microbial prevalence among the fruits sold outside Dhaka Medical College Hospital (DMCH) along with their antimicrobial profiles and to detect antimicrobial resistance genes among the resistant organisms. MethodsThirty-five different types of fruits were bought from around DMCH and analyzed for the presence of bacteria. Antibiotic sensitivity was done and ESBL, AmpC {beta}-lactamase, and MBL positive strains were identified by standard methods followed by PCR to detect ESBL, AmpC {beta}-lactamase, and MBL genes. FindingsTwenty seven different organisms were isolated and identified which were-Klebsiella spp (33{middle dot}33%), Citrobacter spp (29{middle dot}64%), Enterobacter spp (22{middle dot}22%), Escherichia coli (11{middle dot}11%), and Staphylococcus aureus (3{middle dot}70%). Among them 48{middle dot}15% organisms were resistant to different antibiotics. Only one organism (Citrobacter spp) produced ESBL phenotypically (7{middle dot}69%). Two (15{middle dot}38%) were positive for AmpC {beta}-lactamase and one of these (Enterobacter spp) possessed both SHV and CTX-M15A genes by PCR. Imipenem resistance was 84{middle dot}62% of the antibiotic resistant organisms, and 10 (90{middle dot}91%) were phenotypically MBL positive by CD test, DDS test, and MHT. By PCR, one Enterobacter spp had MBL encoding gene OXA-48. InterpretationFresh fruits, contaminated with pathogens, might be a source of transmission of resistant organisms and attribute to public health issues. FundingThe office of Directorate General of Health Service, Ministry of Health and Family Welfare, Bangladesh. ImportanceFruits sold around Dhaka Medical College and Hospital (DMCH) are usually consumed by patients, patients attendant and Health care worker. This investigation emphasized not only on the extent of bacterial contamination but also attempted to measure the anti-microbial profile of these organisms isolated from the fruits commonly available and readily consumed in and around DMCH.

microbiology↗

bioRxiv2021

Bark beetles locate fungal symbionts by detecting volatile fungal metabolites of host tree resin monoterpenes

Outbreaks of the Eurasian spruce bark beetle (Ips typographus) have decimated millions of hectares of conifer forests in Europe in recent years. The ability of these 3-6 mm long insects to kill mature trees over a short period has been ascribed to two main factors: (1) mass attacks on the host tree to overcome tree defenses and (2) the presence of fungal symbionts that support successful beetle development in the tree. While the role of pheromones in coordinating mass attacks has been well studied, the role of chemical communication in maintaining the fungal symbiosis is poorly understood. We previously demonstrated that I. typographus can recognize beneficial fungal symbionts of the genera Grosmannia, Endoconidiophora and Ophiostoma by their de novo synthesized volatile compounds. Here, we hypothesize that the fungal symbionts of the bark beetles might metabolize spruce resin monoterpenes of the beetles host tree, Norway spruce (Picea abies), and that the volatile products could be used as cues by beetles for locating breeding sites with beneficial symbionts. We show that Grosmannia penicillata and other fungal symbionts altered the profile of spruce bark volatiles by converting the major monoterpenes into an attractive blend of oxygenated derivatives. Bornyl acetate was metabolized to camphor, and - and {beta}-pinene to trans-4-thujanol and other oxygenated products. Other co-occurring non-beneficial fungi (Trichoderma sp.) also produce oxygenated monoterpenes, but in non-attractive ratios. Extensive electrophysiological measurements showed that the bark beetle possesses dedicated olfactory sensory neurons for oxygenated metabolites. Compounds such as camphor and trans-4-thujanol attracted beetles at specific doses in olfactory experiments, and the presence of symbiotic fungi enhanced attraction of females to pheromones. Finally, we show that colonization of fungal symbionts on spruce bark diet stimulated beetles to make tunnels into the diet. Collectively, our study suggests that the blends of oxygenated metabolites of conifer monoterpenes produced by fungal symbionts are used by bark beetles as attractive cues to find breeding or feeding sites containing their essential microbial symbionts. The oxygenated metabolites may aid beetles in assessing the presence of the fungus, the defense status of the host tree and the density of conspecifics at potential feeding and breeding sites.

ecology↗

bioRxiv2021

How to attract and retain health workers in rural areas of a fragile state: findings from a labour market survey in Guinea

Most countries face challenges attracting and retaining health staff in remote areas but this is especially acute in fragile and shock-prone contexts, like Guinea, where imbalances in staffing are high and financial and governance arrangements to address rural shortfalls are weak. The objective of this study was to understand how health staff could be better motivated to work and remain in rural, under-served areas in Guinea. In order to inform the policy dialogue on strengthening human resources for health, we conducted three nationally representative cross-sectional surveys, adapted from tools used in other fragile contexts. We found that the locational job preferences of health workers in Guinea are particularly influenced by opportunities for training, working conditions, and housing. Most staff are satisfied with their work and with supervision, however, financial aspects and working conditions are considered least satisfactory, and worrying findings include the high proportion of staff favouring emigration, their high tolerance of informal user payments, as well as their limited exposure to rural areas during training. Based on our findings, we highlight measures which could improve rural recruitment and retention in Guinea and similar settings. These include offering upgrading and specialization in return for rural service; providing greater exposure to rural areas during training; increasing recruitment from rural areas; experimenting with fixed term contracts in rural areas; and improving working conditions in rural posts. The development of incentive packages should be accompanied by action to tackle wider issues, such as reforms to training and staff management.

scientific communication and education↗

bioRxiv2020

LOK/SLK kinases and ERM proteins function together to regulate apical morphology and inhibit RhoA signaling

Activated Ezrin-Radixin-Moesin (ERM) proteins link the plasma membrane to the actin cytoskeleton to generate apical structures, including microvilli. Among many kinases implicated in ERM activation are the homologs LOK and SLK. CRISPR/Cas9 was used to knockout all ERM proteins or LOK/SLK in human cells. LOK/SLK knockout eliminates all ERM activating phosphorylation. The apical domain of cells lacking LOK/SLK or ERMs is strikingly similar and selectively altered, with loss of microvill, and junctional actin replaced by ectopic myosin-II containing apical stress-fiber-like structures. Constitutively active ezrin can reverse the phenotypes of either ERMs or LOK/SLK knockouts, showing that the major function of LOK/SLK is to activate ERMs. Both knockout lines have elevated active RhoA with concomitant enhanced myosin light chain phosphorylation, revealing that active ERMs are negative regulators of RhoA. As RhoA-GTP activates LOK/SLK to activate ERM proteins, the ability of active ERMs to negatively regulate RhoA-GTP represents a novel local feedback loop necessary for the proper apical morphology of epithelial cells.

cell biology↗