Binding and entry of a non-enveloped T=4 insect RNA virus is triggered by alkaline pH
- Penkler, David L, Jiwaji, Meesbah, Domitrovic, Tatiana, Short, James R, Johnson, John E, Dorrington, Rosemary A
- Authors: Penkler, David L , Jiwaji, Meesbah , Domitrovic, Tatiana , Short, James R , Johnson, John E , Dorrington, Rosemary A
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/65995 , vital:28875 , https://doi.org/10.1016/j.virol.2016.08.028
- Description: publisher version , Tetraviruses are small, non-enveloped, RNA viruses that exclusively infect lepidopteran insects. Their particles comprise 240 copies of a single capsid protein precursor (CP), which undergoes autoproteolytic cleavage during maturation. The molecular mechanisms of capsid assembly and maturation are well understood, but little is known about the viral infectious lifecycle due to a lack of tissue culture cell lines that are susceptible to tetravirus infection. We show here that binding and entry of the alphatetravirus, Helicoverpa armigera stunt virus (HaSV), is triggered by alkaline pH. At pH 9.0, wild-type HaSV virus particles undergo conformational changes that induce membrane-lytic activity and binding to Spodoptera frugiperda Sf9 cells. Binding is followed by entry and infection, with virus replication complexes detected by immunofluorescence microscopy within 2 h post-infection and the CP after 12 h. HaSV particles produced in S. frugiperda Sf9 cells are infectious. Helicoverpa armigera larval virus biofeed assays showed that pre-treatment with the V-ATPase inhibitor, Bafilomycin A1, resulted in a 50% decrease in larval mortality and stunting, while incubation of virus particles at pH 9.0 prior to infection restored infectivity. Together, these data show that HaSV, and likely other tetraviruses, requires the alkaline environment of the lepidopteran larval midgut for binding and entry into host cells.
- Full Text: false
- Date Issued: 2016
- Authors: Penkler, David L , Jiwaji, Meesbah , Domitrovic, Tatiana , Short, James R , Johnson, John E , Dorrington, Rosemary A
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/65995 , vital:28875 , https://doi.org/10.1016/j.virol.2016.08.028
- Description: publisher version , Tetraviruses are small, non-enveloped, RNA viruses that exclusively infect lepidopteran insects. Their particles comprise 240 copies of a single capsid protein precursor (CP), which undergoes autoproteolytic cleavage during maturation. The molecular mechanisms of capsid assembly and maturation are well understood, but little is known about the viral infectious lifecycle due to a lack of tissue culture cell lines that are susceptible to tetravirus infection. We show here that binding and entry of the alphatetravirus, Helicoverpa armigera stunt virus (HaSV), is triggered by alkaline pH. At pH 9.0, wild-type HaSV virus particles undergo conformational changes that induce membrane-lytic activity and binding to Spodoptera frugiperda Sf9 cells. Binding is followed by entry and infection, with virus replication complexes detected by immunofluorescence microscopy within 2 h post-infection and the CP after 12 h. HaSV particles produced in S. frugiperda Sf9 cells are infectious. Helicoverpa armigera larval virus biofeed assays showed that pre-treatment with the V-ATPase inhibitor, Bafilomycin A1, resulted in a 50% decrease in larval mortality and stunting, while incubation of virus particles at pH 9.0 prior to infection restored infectivity. Together, these data show that HaSV, and likely other tetraviruses, requires the alkaline environment of the lepidopteran larval midgut for binding and entry into host cells.
- Full Text: false
- Date Issued: 2016
Developmental and spatial variations in the diet signatures of hyperbenthic shrimp Nauticaris marionis at the Prince Edward Islands based on stable isotope ratios and fatty acid profiles
- Richoux, Nicole B, Allan, Elizabeth L, Froneman, P William
- Authors: Richoux, Nicole B , Allan, Elizabeth L , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67923 , vital:29169 , https://doi.org/10.1016/j.csr.2016.02.0131
- Description: Publisher version , The caridean shrimp Nauticaris marionis is an ecologically important species in the benthic community around the sub-Antarctic Prince Edward Islands (PEI) as it represents a key prey item for a variety of top predators breeding on the islands. We hypothesized that the diet of N. marionis shifts during its development, and that spatial variability in food availability results in differentiation in the diet signatures of specimens collected from various locations of the shelf waters around the PEI. Specimens were collected from nine stations (depth range 70 to 240 m) around the PEI at inter-island shelf (from west to east: upstream, between and downstream) and nearshore regions during austral autumn 2009. Stable isotope and fatty acid data both revealed spatial and developmental variations in the shrimp diet. Nearshore shrimp were more 13C-enriched than those from the inter-island region, suggesting increased kelp detritus entered the food web in the nearshore regions. The shrimp showed increases in δ13C and δ15N signatures (and trophic position) with an increase in body size, resulting in distinctions between size classes that reflected shifts in their trophic niche through development. The fatty acid profiles similarly indicated distinctions in diet with increased shrimp size (in the deep regions), and spatial variability was evident in relation to region and depth. All shrimp contained large proportions of polyunsaturated and essential fatty acids, indicating that the quality of food consumed was similar between regions despite the diet variability. Our results provide new dietary information about a key species operating near the base of the food web at the highly productive PEI, and show that there were no areas of enhanced nutrition available to the shrimp. As such, there was no nutritional advantage to shrimp inhabiting any specific region around the PEI.
- Full Text: false
- Date Issued: 2016
- Authors: Richoux, Nicole B , Allan, Elizabeth L , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67923 , vital:29169 , https://doi.org/10.1016/j.csr.2016.02.0131
- Description: Publisher version , The caridean shrimp Nauticaris marionis is an ecologically important species in the benthic community around the sub-Antarctic Prince Edward Islands (PEI) as it represents a key prey item for a variety of top predators breeding on the islands. We hypothesized that the diet of N. marionis shifts during its development, and that spatial variability in food availability results in differentiation in the diet signatures of specimens collected from various locations of the shelf waters around the PEI. Specimens were collected from nine stations (depth range 70 to 240 m) around the PEI at inter-island shelf (from west to east: upstream, between and downstream) and nearshore regions during austral autumn 2009. Stable isotope and fatty acid data both revealed spatial and developmental variations in the shrimp diet. Nearshore shrimp were more 13C-enriched than those from the inter-island region, suggesting increased kelp detritus entered the food web in the nearshore regions. The shrimp showed increases in δ13C and δ15N signatures (and trophic position) with an increase in body size, resulting in distinctions between size classes that reflected shifts in their trophic niche through development. The fatty acid profiles similarly indicated distinctions in diet with increased shrimp size (in the deep regions), and spatial variability was evident in relation to region and depth. All shrimp contained large proportions of polyunsaturated and essential fatty acids, indicating that the quality of food consumed was similar between regions despite the diet variability. Our results provide new dietary information about a key species operating near the base of the food web at the highly productive PEI, and show that there were no areas of enhanced nutrition available to the shrimp. As such, there was no nutritional advantage to shrimp inhabiting any specific region around the PEI.
- Full Text: false
- Date Issued: 2016
Distribution of benthic diatom communities in a permanently open temperate estuary in relation to physico-chemical variables
- Dalu, Tatenda, Richoux, Nicole B, Froneman, P William
- Authors: Dalu, Tatenda , Richoux, Nicole B , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67943 , vital:29172 , https://doi.org/10.1016/j.sajb.2015.06.004
- Description: Publisher version , The spatial and temporal patterns in benthic diatom community structure in temperate permanently open estuaries are poorly understood. In this study, we used a combination of multivariate and diversity indices to elucidate environmental factors associated with diatom community structure in the Kowie Estuary, South Africa. Benthic diatom samples were collected from three sites corresponding to the upper, middle and lower reaches of the estuary on four occasions over the period early spring 2012 to winter 2013. Among the 89 benthic diatoms observed, Entomoneis paludosa (W Smith) Reimer, Nitzschia reversa W Smith, Nitzschia closterium (Ehrenberg) W Smith, Pleurosigma elongatum W Smith, P. salinarum (Grunow) Grunow, Staurosira elliptica (Schumann) DM Williams & Round, Surirella brebissonii Krammer & Lange-Bertalot, and Surirella ovalis Brébisson were the numerically dominant species. Principal component analysis demonstrated that the diatom community structure was determined by a variety of factors including nutrient (ammonia, nitrate) concentrations, hydrology (e.g., water depth and flow) and pH. Hierarchical cluster analysis revealed the absence of any distinct spatial patterns, although distinct benthic diatom communities were recorded during the different sampling periods. The species richness was highest in the middle reach, decreasing from early spring to summer in all reaches. The results of the study provide important insights into the various factors that structure benthic diatom community composition within a permanently open temperate southern African estuary.
- Full Text: false
- Date Issued: 2016
- Authors: Dalu, Tatenda , Richoux, Nicole B , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67943 , vital:29172 , https://doi.org/10.1016/j.sajb.2015.06.004
- Description: Publisher version , The spatial and temporal patterns in benthic diatom community structure in temperate permanently open estuaries are poorly understood. In this study, we used a combination of multivariate and diversity indices to elucidate environmental factors associated with diatom community structure in the Kowie Estuary, South Africa. Benthic diatom samples were collected from three sites corresponding to the upper, middle and lower reaches of the estuary on four occasions over the period early spring 2012 to winter 2013. Among the 89 benthic diatoms observed, Entomoneis paludosa (W Smith) Reimer, Nitzschia reversa W Smith, Nitzschia closterium (Ehrenberg) W Smith, Pleurosigma elongatum W Smith, P. salinarum (Grunow) Grunow, Staurosira elliptica (Schumann) DM Williams & Round, Surirella brebissonii Krammer & Lange-Bertalot, and Surirella ovalis Brébisson were the numerically dominant species. Principal component analysis demonstrated that the diatom community structure was determined by a variety of factors including nutrient (ammonia, nitrate) concentrations, hydrology (e.g., water depth and flow) and pH. Hierarchical cluster analysis revealed the absence of any distinct spatial patterns, although distinct benthic diatom communities were recorded during the different sampling periods. The species richness was highest in the middle reach, decreasing from early spring to summer in all reaches. The results of the study provide important insights into the various factors that structure benthic diatom community composition within a permanently open temperate southern African estuary.
- Full Text: false
- Date Issued: 2016
The effect of land-use on small mammal diversity inside and outside the Great Fish River Nature Reserve, Eastern Cape, South Africa
- Thondhlana, Gladman, Lagesse, Juliette V
- Authors: Thondhlana, Gladman , Lagesse, Juliette V
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67823 , vital:29150 , https://doi.org/10.1016/j.jaridenv.2016.03.006
- Description: Publisher version , This study investigated small mammal species diversity at 10 paired contrast sites along a fence line inside and outside the Great Fish River Nature Reserve (GFRNR), Eastern Cape, South Africa. The sites outside the GFRNR are used for subsistence land-based activities including livestock production and fuelwood harvesting. From 145 live captures, a total of 114 unique individuals of five small mammal species (four rodents and one elephant shrew) were recorded over 1170 trap nights. Average small mammal species diversity and abundance were significantly higher inside the reserve than outside. Human activities such as livestock grazing seemed to explain low levels of small mammal diversity and abundance at the communal sites. Vegetation variables showed a complex interplay with small mammal diversity. In general, high vegetation diversity had a positive influence on small mammal diversity though the influence of some environmental variables was species-dependent. We conclude that the GFRNR is effective in protecting small mammals but the findings raise questions around the influence of land use practices such as livestock grazing on biodiversity, especially given that local communities in South Africa are continuously seeking greater access to reserves for livestock grazing and other provisioning services.
- Full Text: false
- Date Issued: 2016
- Authors: Thondhlana, Gladman , Lagesse, Juliette V
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67823 , vital:29150 , https://doi.org/10.1016/j.jaridenv.2016.03.006
- Description: Publisher version , This study investigated small mammal species diversity at 10 paired contrast sites along a fence line inside and outside the Great Fish River Nature Reserve (GFRNR), Eastern Cape, South Africa. The sites outside the GFRNR are used for subsistence land-based activities including livestock production and fuelwood harvesting. From 145 live captures, a total of 114 unique individuals of five small mammal species (four rodents and one elephant shrew) were recorded over 1170 trap nights. Average small mammal species diversity and abundance were significantly higher inside the reserve than outside. Human activities such as livestock grazing seemed to explain low levels of small mammal diversity and abundance at the communal sites. Vegetation variables showed a complex interplay with small mammal diversity. In general, high vegetation diversity had a positive influence on small mammal diversity though the influence of some environmental variables was species-dependent. We conclude that the GFRNR is effective in protecting small mammals but the findings raise questions around the influence of land use practices such as livestock grazing on biodiversity, especially given that local communities in South Africa are continuously seeking greater access to reserves for livestock grazing and other provisioning services.
- Full Text: false
- Date Issued: 2016
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