The life cycle and enigmatic egress of coronaviruses

There has been considerable recent interest in the life cycle of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), the causative agent of the Covid-19 pandemic. Practically every step in CoV replication—from cell attachment and uptake via genome replication and expression to virion assembly has been considered as a specific event that potentially could be targeted by existing or novel drugs. Interference with cellular egress of progeny viruses could also be adopted as a possible therapeutic strategy; however, the situation is complicated by the fact that there is no broad consensus on how CoVs find their way out of their host cells. The viral nucleocapsid, consisting of the genomic RNA complexed with nucleocapsid proteins obtains a membrane envelope during virus budding into the lumen of the intermediate compartment (IC) at the endoplasmic reticulum (ER)–Golgi interface. From here, several alternative routes for CoV extracellular release have been proposed. Strikingly, recent studies have shown that CoV infection leads to the disassembly of the Golgi ribbon and the mobilization of host cell compartments and protein machineries that are known to promote Golgi-independent trafficking to the cell surface. Here, we discuss the life cycle of CoVs with a special focus on different possible pathways for virus egress.publishedVersio

Editorial: Golgi Dynamics in Physiological and Pathological Conditions

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Evidence for the role of Rab11-positive recycling endosomes as intermediates in coronavirus egress from epithelial cells

After their assembly by budding into the lumen of the intermediate compartment (IC) at the endoplasmic reticulum (ER)–Golgi interface, coronaviruses (CoVs) are released from their host cells following a pathway that remains poorly understood. The traditional view that CoV exit occurs via the constitutive secretory route has recently been questioned by studies suggesting that this process involves unconventional secretion. Here, using the avian infectious bronchitis virus (IBV) as a well-established model virus, we have applied confocal microscopy to investigate the pathway of CoV egress from epithelial Vero cells. We report a novel effect of IBV infection on cellular endomembranes, namely, the compaction of the pericentrosomal endocytic recycling compartment (ERC) defined by the GTPase Rab11, which coincides with the previously described Golgi fragmentation, as well as virus release. Despite Golgi disassembly, the IC elements containing the major IBV membrane protein (M)—which mostly associates with newly formed virus particles—maintain their close spatial connection with the Rab11-positive endocytic recycling system. Moreover, partial colocalization of the M protein with Rab11 was observed, whereas M displayed negligible overlap with LAMP-1, indicating that IBV egress does not occur via late endosomes or lysosomes. Synchronization of virus release using temperature-shift protocols was accompanied by increased colocalization of M and Rab11 in vesicular and vacuolar structures in the pericentrosomal region and at the cell periphery, most likely representing IBV-containing transport carriers. In conclusion, these results add CoVs to the growing list of viruses exploiting the endocytic recycling apparatus defined by Rab11 for their assembly and/or release.publishedVersio

Assessment of genetically modified maize MON 95379 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 (application EFSA‐GMO‐NL‐2020‐170)

Event MON 95379 is a genetically modified maize developed by a two-step process. In the first step, immature embryos of maize inbred line LH244 were co-cultured with a disarmed Agrobacterium tumefaciens (also known as Rhizobium radiobacter) strain ABI containing the vector PV-ZMIR522223. In the second step, selected R2 lines were crossed with maize inbred LH244 line expressing Crerecombinase, which had been transformed with vector PVZMOO513642. In the resulting plants, the CP4 EPSPS-cassette (used for selection of transformed plants) was excised by the Cre recombinase, and the Cre gene was subsequently segregated away, through conventional breeding, to obtain maize MON 95379. Maize MON 95379 expresses Cry1B.868, a chimeric protein containing domains from Cry1A, Cry1B and Cry1C naturally expressed in Bacillus thuringiensis, and Cry1Da_7, an optimised version of Cry1Da carrying four amino acids substitutions to increase its activity. The two Cry proteins expressed in maize MON 95379 provide protection against targeted pests within the order of butterflies and moths (Lepidoptera) including fall armyworm (Spodoptera frugiperda), sugarcane borer (Diatraea saccharalis) and corn earworm (Helicoverpa zea). The scientific documentation provided in the application for genetically modified maize MON 95379 is adequate for risk assessment, and in accordance with EFSA guidance on risk assessment of genetically modified plants for use in food or feed. The VKM GMO panel does not consider the introduced modifications in event MON 95379 to imply potential specific health or environmental risks in Norway, compared to EU-countries. The EFSA opinion is adequate also for Norwegian considerations. Therefore, a full risk assessment of event MON 95379 was not performed by the VKM GMO Panel.Assessment of genetically modified maize MON 95379 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 (application EFSA‐GMO‐NL‐2020‐170)publishedVersio

Assessment of genetically modified maize MON 87429 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2019-161)

Event MON 87429 is a genetically modified maize developed via Agrobacterium tumefaciens transformation. MON 87429 plants contain the transgenes pat, dmo, ft_t and cp4 epsps. Maize MON 87429 encodes the DMO, PAT and FT_T proteins. In addition, maize MON 87429 encodes the CP4 EPSPS protein and utilises an endogenous maize RNAi regulatory element to suppress its expression in pollen. This results in a lack of viable pollen and thus male sterility when MON 87429 plants are exposed to glyphosate-containing herbicides at growth stages ranging from V8 to V13. This is part of a hybridisation system to be used in inbred lines to facilitate the hybrid seeds production. This is not considered an agronomic trait since the application of glyphosate outside the specific growth stages does not lead to male sterile plants but reduces plant yield compared to plants not expressing the same trait. The scientific documentation provided in the application for genetically modified maize MON 87429 is adequate for risk assessment, and in accordance with EFSA guidance on risk assessment of genetically modified plants for use in food or feed. The VKM GMO panel does not consider the introduced modifications in event MON 87429 to imply potential specific health or environmental risks in Norway, compared to EU-countries. The EFSA opinion is adequate also for Norwegian considerations. Therefore, a full risk assessment of event MON87429 was not performed by the VKM GMO PanelAssessment of genetically modified maize MON 87429 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2019-161)publishedVersio

Assessment of genetically modified soybean MON 87701 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 (renewal application EFSA-GMO-RX-021)

Event MON 87701 is a genetically modified soybean developed via Agrobacterium tumefaciens transformation. MON 87701 plants contain the transgene cry1Ac which encodes the protein Cry1Ac. The protein Cry1Ac provides resistance against specific lepidopteran pests. The scientific documentation provided in the renewal application (EFSA-GMO-RX-021) for soybean MON 87701 is adequate for risk assessment, and in accordance with EFSA guidance on risk assessment of genetically modified plants for use in food or feed. The VKM GMO panel does not consider the introduced modifications in soybean MON 87701 to imply potential specific health or environmental risks in Norway, compared to EU-countries. The EFSA opinion is adequate also for Norwegian considerations. Therefore, a full risk assessment of event MON 87701 was not performed by the VKM GMO Panel.Assessment of genetically modified soybean MON 87701 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 (renewal application EFSA-GMO-RX-021)publishedVersio

Assessment of genetically modified maize MON 87419 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2017-140)

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Assessment of genetically modified maize GA21 x T25 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2016-137)

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