SACM - United Kingdom
Permanent URI for this collectionhttps://drepo.sdl.edu.sa/handle/20.500.14154/9667
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Item Embargo Characterisation of a virulence associated metal resistance operon in the food-borne pathogen Campylobacter jejuni(University of Manchester, 2024) Al khaldi, Jawahir; Cavet, JenniferCampylobacter jejuni is the primary bacterial cause of foodborne gastroenteritis globally. Within the food chain and during colonisation and infection of its hosts, C. jejuni must tolerate a variety of environmental stresses, both inside and outside the host, including fluxes in metal levels and exposure to reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive chlorine species (RCS) associated with host innate immune defences and food processing. Within the C. jejuni NCTC 11168 genome, czcD and copA are located within a four gene operon, cj1164c-cj 1161c (designated cmr), encoding zinc and copper exporters from the Cation Diffusion Facilitator (CDF) and P1B-type ATPase families, respectively. In addition to zinc and copper resistance, this work has demonstrated that both CzcD and CopA in C. jejuni also contribute to tolerance to ROS and bile deoxycholate, whilst CopA was also provides resistance to RNS. The regulation of the cmr operon promoter (Pcmr) was investigated, with zinc, copper and cobalt shown to induce transcription as well as ROS, consistent with the operon being associated with resistance to these stresses. Notably, a role for Fur in regulating expression from Pcmr in response to zinc and ROS has been demonstrated, whilst PerR has also been shown to influence expression in response to ROS. Accumulation of manganese is reported to be important in ROS resistance in bacteria and these studies have demonstrated that manganese accumulation is important for protecting C. jejuni from oxidative stress. However, despite zinc exposure causing manganese-depletion in C. jejuni, manganese does not provide protection against zinc-toxicity. As part of these investigations, two systems involved in C. jejuni NCTC 11168 manganese import have been identified, with both cj0141c that encodes the deduced inner membrane permease of an MntB-like ABC transporter and zupT (cj0263) that encodes a ZIP family transporter being required for maintaining cellular manganese levels, with cj0141c being essential for growth in the absence of manganese or zinc supplementation. This report confirmed a requirement for Cj0141c for manganese accumulation in C. jejuni to levels that are sufficient to confer protection against oxidative stress and aerobic conditions. Overall, this study has further defined the roles of CzcD and CopA in protecting C. jejuni from antimicrobial stresses and the factors associated with regulating their production, in addition to identifying the systems associated with maintaining manganese homeostasis in this important foodborne pathogen.13 0Item Restricted Exploring the Role of Prostaglandin G/H Synthase Signalling in Chemoresistance in Acute Myeloid Leukaemia(University of Liverpool, 2024-03-05) Alshammari, Abdullah Mohammad D; Woolley, John; MacEwan, DaveAntioxidant signalling is demonstrated to be important for leukemic stem cell (LSC) and haematopoietic stem cell (HSC) function. HSCs, which are found in the bone marrow, are found to be more quiescent under hypoxic conditions. Reduced cell division creates problems for these cells, with the majority of cells using this process to address oxidative damaged DNA and proteins. In this situation, HSCs must approach oxidative damage management in other ways. Prostaglandins improve mechanisms to protect from oxidative stresses through causing reductions in reactive oxygen species (ROS). Prostaglandin G/H synthases (PTGS1/2) play the main role in catalysing synthesis of prostaglandins. Research has demonstrated that PGE2, produced through PTGS1/2 activity, assists HSCs in surviving, proliferating and homing within their niche. Similarly, the data provided in this study points to a protective function of PTGS1/2 signal pathways for acute myeloid leukaemia. PTGS genes were investigated for their association with outcomes in AML, in an approach combining biochemistry, bioinformatics, molecular biology and cellular biology. Analysis of bioinformatics databases aimed to assess how PTGS1/2 was expressed in AML and the effects of this expression on outcomes including overall survival. An efficacy assessment was made for PTGS1 inhibitors (SC560, Tenidap) for AML cell lines. Flow cytometry was used to evaluate the cell cycle and apoptosis. Lentiviral PTGS1/2 over-expression was used for U937 and HL-60 in order to assess how these genes act in cell survival, proliferative activity and resistance to drugs. Finally, PTGS1/2 was analysed in terms of promotion of immunosuppression in acute myeloid leukaemia. Investigation of freely accessible bioinformatics databases demonstrated increased PTGS1 expression in the HSC, which reduced in cells committed to a lineage for myeloid progenitor cells. This was not found for PTGS2. There is a notable association between increased expression of PTGS1 and lower overall survival in data on AML (TCGA, Verhaak), with none seen for PTGS2. Findings in vitro show that inhibiting PTGS1 (SC560, Tenidap) leads to decreased growth of cells, arrests the cell cycle and elevates apoptosis. Overexpressed PTGS1 leads to higher WNT signalling for AML cell lines, as well as raising PGE2 secretions and reversing PTGS1 inhibitor impacts. Other effects of increased PTGS1 expression include resistance to cytarabine, as linked with lower generation of ROS. It is notable that overexpression of PTGS1 and PTGS2 lead to significant differences in transcriptome alterations in AML, which could explain the varied patient outcomes with PTGS1/2 overexpression.18 0Item Restricted Dissecting the role of cytokinin in root response to heat stress in Arabidopsis thaliana.(Saudi Digital Library, 2023-12-12) Aljohani, Thamir; Bhosale, Rahul; Bishopp, Anthony; Lale, AneeshGlobal food security is threatened by rising temperatures, which impair crop productivity. This study aimed to elucidate the molecular mechanisms enabling plant root adaptation to heat stress, focusing on the roles of cytokinin signalling, reactive oxygen species (ROS) regulation, and apoplastic pH in modulating root system resilience in Arabidopsis thaliana. Exogenous cytokinin application was found to enhance thermotolerance by reducing oxidative damage through ROS modulation in roots, although receptor mutants failed to exhibit similar antioxidant effects. Cytokinin was found to induce dynamic spatiotemporal alterations in apoplastic pH within root tissues. Moreover, a bidirectional relationship was revealed between cytokinin and pH, with exogenous pH changes reciprocally impacting cytokinin signalling intensity in roots. Acidic pH enhanced cytokinin responses, uncovering pH-mediated modulation of hormone signalling as a key factor in stress adaptation. This highlights the interconnectedness of hormonal, metabolic, and physiological factors orchestrating stress adaptation through a complex molecular interplay within plant root systems. The key findings significantly advance mechanistic understanding of the factors enabling root architecture preservation and function under temperature extremes. They provide a foundation for targeted interventions via biotechnology or agricultural strategies to improve crop heat tolerance and climate resilience by enhancing root thermotolerance. However, further validation across diverse genetic backgrounds is essential before translating these fundamental insights into implementable solutions. Overall, by elucidating the crosstalk between cytokinin, ROS, and apoplastic pH in the heat response in roots, this research makes important strides toward enabling precise crop improvement under global climate change.11 0