Comparative ultrastructural analyses of rhabdovirus replication in plants and animals

ID: LS1.P010 Type: Abstract poster Session: ePosters LS ePosters LS 1 Speaker: Katja R. Richert-Pöggeler (Braunschweig/DE) Authors: Katja R. Richert-Pöggeler (Braunschweig/DE), Kati Franzke (Greifswald -Insel Riems/DE) Introduction: Virus evolution is assumed to start from precellular replicons that combined with escaped genes forming protocapsids from primitive cells. Enveloped viruses, like vertebrate, invertebrate and plant infecting rhabdoviridae originated later in evolution when modern cells entered the stage. This virus family encapsidating a negative sense ssRNA genome is quite successful in finding cellular niches for replication. Rhabdoviridae can be found in symbiosis with aquatic as well as teresstrial hosts. The observed emergence of rhabdoviruses is illustrated by a five fold increase in number of virus genera within the last decade. Objectives: Comparative ultrastructural analyses of rhabdovirus replication in plants and animals to investigate rhabdovirus plasticity and evolution at the cellular level. Rhabdovirus developmental stages in naturally as well as artificially infected hosts are studied. Materials and methods: For electron microscopy, small pieces of symptomatic leaves were directly homogenized in 2% ammonium molybdate, pH 6.5 with one drop of 0.5% bovine serum albumin (BSA) added. In addition, leaves of systemically infected plants were embedded in Epon 812 after consecutive fixation of samples with 2.5% glutaraldehyde and 0.5% osmium tetroxide. Grids were examined in a Tecnai G2 Spirit electron microscope at 80 kV. Images were taken with a 2K Veleta camera. Specificity of polyclonal antisera was tested in IEM. Results: Despite distinct grades in symptom expression the ultrastructure of infected cells is similar in natural and artificial hosts. A polarity in bacilliform shaped virions is visible during disassembly. During assembly virions appear in parallel arrays within the nuclear matrix next to the nuclear envelope. In later stages of infection the heterochromatin is more and more replaced by viroplasmn and budding virons. Besides the nucleus, chloroplasts organization is disturbed and in one case, stromules were visible. Conclusions: Both cytoplasmic and nuclear RNA interactome offer niches for rhabdovirus replication. Embodyment of the host nuclear membrane system for envelope production enables plant rhabdovirus replication in related (lamiales and solanales) as well as distinct (fabales and solanales) plant orders. We are currently applying a double stranded (ds)RNA binding antibody to identify rhabdovirus replication intermediates in the cell.


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