Non-random organization of the Biomphalaria glabrata genome in interphase Bge cells and the spatial repositioning of activated genes in cells co-cultured with Schistosomamansoni

Biomphalaria glabrata is a major intermediate host for the parasitic trematode Schistosoma mansoni, a causative agent of human schistosomiasis. To decipher the molecular basis of this host-parasite interaction, the Bge embryonic cell line provides a unique in vitro model system to assess whether interactions between the snail and parasite affect the cell and genome biology in either organism. The organization of the B. glabrata genome in Bge cells was studied using image analysis through positioning territories of differently sized chromosomes within cell nuclei. The snail chromosome territories are similar in morphology as well as in non-random radial positioning as those found in other derived protostome and deuterostome organisms. Specific monitoring of four gene loci, piwi, BgPrx, actin and ferritin, revealed non-random radial positioning of the genome. This indicates that specific parts of the snail genome reside in reproducible nuclear addresses. To determine whether exposure to parasite is reflected in genome organization, the interphase spatial positioning of genes was assessed after co-culturing Bge cells with either normal or irradiation attenuated miracidia for 30 min to 24 h. The loci of actin and ferritin, genes that are up-regulated in the snail when subjected to infection, were visualized by fluorescence in situ hybridisation (FISH) and their radial nuclear positions i.e. their position in the interphase nucleus with respect to the nuclear edge/envelope, mapped. Interestingly, large scale gene repositioning correlated to temporal kinetics of gene expression levels in Bge cells co-cultured with normal miracidia while irradiated parasites failed to elicit similar gene expression or gene loci repositioning as demonstrated using the ferritin gene. This indicates that normal but not attenuated schistosomes provide stimuli that evoke host responses that are reflected in the host’s nuclear architecture. We believe that this is not only the first time that gene-repositioning studies have been attempted in a mollusc but also demonstrates a parasite influencing the interphase genome organization of its host.     

Differential Spatial Repositioning of Activated Genes in Biomphalaria glabrata Snails Infected with Schistosoma mansoni

Schistosomiasis is an infectious disease infecting mammals as the definitive host and fresh water snails as the intermediate host. Understanding the molecular and biochemical relationship between the causative schistosome parasite and its hosts will be key to understanding and ultimately treating and/or eradicating the disease. There is increasing evidence that pathogens that have co-evolved with their hosts can manipulate their hosts'' behaviour at various levels to augment an infection. Bacteria, for example, can induce beneficial chromatin remodelling of the host genome. We have previously shown in vitro that Biomphalaria glabrata embryonic cells co-cultured with schistosome miracidia display genes changing their nuclear location and becoming up-regulated. This also happens in vivo in live intact snails, where early exposure to miracidia also elicits non-random repositioning of genes. We reveal differences in the nuclear repositioning between the response of parasite susceptible snails as compared to resistant snails and with normal or live, attenuated parasites. Interestingly, the stress response gene heat shock protein (Hsp) 70 is only repositioned and then up-regulated in susceptible snails with the normal parasite. This movement and change in gene expression seems to be controlled by the parasite. Other differences in the behaviour of genes support the view that some genes are responding to tissue damage, for example the ferritin genes move and are up-regulated whether the snails are either susceptible or resistant and upon exposure to either normal or attenuated parasite. This is the first time host genome reorganisation has been seen in a parasitic host and only the second time for any pathogen. We believe that the parasite elicits a spatio-epigenetic reorganisation of the host genome to induce favourable gene expression for itself and this might represent a fundamental mechanism present in the human host infected with schistosome cercariae as well as in other host-pathogen relationships.     

Unusual glycosides of pyrrole alkaloid and 4'-hydroxyphenylethanamide from leaves of Moringa oleifera

Glycosides of pyrrole alkaloid (pyrrolemarumine 4″-O-α-l-rhamnopyranoside) and 4′-hydroxyphenylethanamide (marumosides A and B) were isolated from leaves of Moringa oleifera along with eight known compounds; niazirin, methyl 4-(α-l-rhamnopyranosyloxy)benzylcarbamate, benzyl β-d-glucopyranoside, benzyl β-d-xylopyranosyl-(1 → 6)-β-d-glucopyranoside, kaempferol 3-O-β-d-glucopyranoside, quercetin 3-O-β-d-glucopyranoside, adenosine and l-tryptophan. Structure elucidations were based on analyses of chemical and spectroscopic data including 1D- and 2D-NMR.     

Identification of Carboxylesterase Genes Implicated in Temephos Resistance in the Dengue Vector Aedes aegypti

Background

Thailand is currently experiencing one of its worst dengue outbreaks in decades. As in most countries where this disease is endemic, dengue control in Thailand is largely reliant on the use of insecticides targeting both immature and adult stages of the Aedes mosquito, with the organophosphate insecticide, temephos, being the insecticide of choice for attacking the mosquito larvae. Resistance to temephos was first detected in Aedes aegypti larvae in Thailand approximately 25 years ago but the mechanism responsible for this resistance has not been determined.

Principal Findings

Bioassays on Ae. aegypti larvae from Thailand detected temephos resistance ratios ranging from 3.5 fold in Chiang Mai to nearly 10 fold in Nakhon Sawan (NS) province. Synergist and biochemical assays suggested a role for increased carboxylesterase (CCE) activities in conferring temephos resistance in the NS population and microarray analysis revealed that the CCE gene, CCEae3a, was upregulated more than 60 fold in the NS population compared to the susceptible population. Upregulation of CCEae3a was shown to be partially due to gene duplication. Another CCE gene, CCEae6a, was also highly regulated in both comparisons. Sequencing and in silico structure prediction of CCEae3a showed that several amino acid polymorphisms in the NS population may also play a role in the increased resistance phenotype.

Significance

Carboxylesterases have previously been implicated in conferring temephos resistance in Ae aegypti but the specific member(s) of this family responsible for this phenotype have not been identified. The identification of a strong candidate is an important step in the development of new molecular diagnostic tools for management of temephos resistant populations and thus improved control of dengue.     

The effect of low-pressure carbonation on the heat inactivation of Escherichia coli

The heat inactivating effect of low-pressure carbonation (LPC) at 1 MPa against Escherichia coli was enhanced to 3.5log orders. This study aimed to investigate the mechanisms of this increase in heat inactivation efficiency. The increased inactivation ratio was found to be the result of LPC-induced heat sensitization. This sensitization was not due to any physical damage to the cells as a result of the treatment. Following the depletion of intracellular ATP, the failure of the cells to discard protons caused an abnormal decrease in the intracellular pH. However, in the presence of glucose, the inactivation ratio decreased. In addition, a further increase in inactivation of more than 2log orders occurred in the presence of the protein synthesis inhibitor chloramphenicol. Hence, the decreased heat resistance of E. coli under LPC was most likely due to a depletion of intracellular ATP and a decreased capacity for protein synthesis.     

Resistance Induction by Salicylic Acid Formulation in Cassava Plant against Fusarium solani

Fusarium root rot caused by the soil-borne fungus Fusarium solani is one of the most important fungal diseases of cassava in Thailand, resulting in high yield losses of more than 80%. This study aimed to investigate if the exogenous application of salicylic acid formulations (Zacha) can induce resistance in cassava against Fusarium root rot and observe the biochemical changes in induced cassava leaf tissues through synchrotron radiation based on Fourier-transform infrared (SR-FTIR) microspectroscopy. We demonstrated that the application of Zacha11 prototype formulations could induce resistance against Fusarium root rot in cassava. The in vitro experimental results showed that Zacha11 prototype formulations inhibited the growth of F. solani at approximately 34.83%. Furthermore, a significant reduction in the disease severity of Fusarium root rot disease at 60 days after challenge inoculation was observed in cassava plants treated with Zacha11 at a concentration of 500 ppm (9.0%). Population densities of F. solani were determined at 7 days after inoculation. Treatment of the Zacha11 at a concentration of 500 ppm resulted in reduced populations compared with the distilled water control and differences among treatment means at each assay date. Moreover, the SR-FTIR spectral changes of Zacha11-treated epidermal tissues of leaves had higher integral areas of lipids, lignins, and pectins (1,770–1,700/cm), amide I (1,700–1,600/cm), amide II (1,600–1,500/cm), hemicellulose, lignin (1,300–1,200/cm), and cellulose (1,155/cm). Therefore, alteration in defensive carbohydrates, lipids, and proteins contributed to generate barriers against Fusarium invasion in cassava roots, leading to lower the root rot disease severity.     

Tumor Necrosis Factor and Schistosoma mansoni egg antigen omega-1 shape distinct aspects of the early egg-induced granulomatous response

Infections by schistosomes result in granulomatous lesions around parasite eggs entrapped within the host tissues. The host and parasite determinants of the Schistosoma mansoni egg-induced granulomatous response are areas of active investigation. Some studies in mice implicate Tumor Necrosis Factor (TNF) produced in response to the infection whereas others fail to find a role for it. In addition, in the mouse model, the S. mansoni secreted egg antigen omega-1 is found to induce granulomas but the underlying mechanism remains unknown. We have recently developed the zebrafish larva as a model to study macrophage recruitment and granuloma formation in response to Schistosoma mansoni eggs. Here we use this model to investigate the mechanisms by which TNF and omega-1 shape the early granulomatous response. We find that TNF, specifically signaling through TNF receptor 1, is not required for macrophage recruitment to the egg and granuloma initiation but does mediate granuloma enlargement. In contrast, omega-1 mediates initial macrophage recruitment, with this chemotactic activity being dependent on its RNase activity. Our findings further the understanding of the role of these host- and parasite-derived factors and show that they impact distinct facets of the granulomatous response to the schistosome egg.