Figure 1 (Top left) Outer shell of invertebrate iridescent virus 2 (IIV-2) (from Wrigley et al. (1969). J. Gen. Virol., 5, 123; with permission). (Top right) Schematic diagram of a cross-section of an iridovirus particle, showing capsomers, transmembrane proteins within the lipid bilayer, and an internal filamentous nucleoprotein core (from Darcy-Tripier et al. (1984). Virology, 138, 287; with permission). (Bottom left) Transmission electron micrograph of a fat head minnow cell infected with an isolate of European catfish virus. Nucleus (nu); virus inclusion body (VIB); paracrystalline array of non-enveloped virus particles (arrows); incomplete nucleocapsids (arrowheads); cytoplasm (cy); mitochondrion (mi); the bar represents 1 µm (from Hyatt et al. (2000). Arch. Virol., 145, 301; with permission). (insert) Transmission electron micrograph of particles of frog virus 3 (FV-3), budding from the plasma membrane. Arrows and arrowheads identify the viral envelope; the bar represents 200 nm

(from Devauchelle et al. (1985). Curr. Topics Microbiol. Immunol., 116, 1; with permission.)

Figure 2 Three-dimensional reconstruction of an IIV-6 particle at a resolution of 1.3 nm. (A) 3-D density map of particle viewed along an icosahedral two-fold axis. The external fringe of filaments has been blurred away due to their varying position in relation to the symmetry of the capsid. (B) Central cross-section, one pixel thick. A lipid bilayer follows the inner contour and icosahedral symmetry of the capsid shell whereas the core appears to lack any structures that are arranged following icosahedral symmetry. (C) Magnified view of the central region outlined in (A). The diagonal white line indicates the cleavage plane between adjacent trisymmetrons. (D) Magnified view of the propeller-like pentamer complex at the five-fold vertex. This complex differs from the trimeric capsomers in that it is larger, has a small axial hole, and lacks an external fibre. (E) Magnified view of boxed region in (B) showing transverse section of the pentamer complex and adjacent trisymmetrons. (F) Same as (E) but with the pentamer complex, three capsomers, and their fibres individually outlined. (G) Transmembrane anchor proteins beneath the pentasymmetrons showing two sticklike entities. The longer of the two (long arrow) crosses both leaflets of the bilayer, whereas the other (short arrow) stops at the outer leaflet of the internal lipid membrane.

(From Yan et al. (2009). J. Mol. Biol., 385, 1287–1299; with permission.)

Figure 3 Schematic planar diagram of the IIV-6 capsid structure with the central pentamer complex (white pentagon) omitted for clarity. The centrally located white ellipse, triangle and pentagon symbols highlight the positions of 2-, 3-, and 5-fold icosahedral axes, respectively. All major capsid protein trimers are shown as three small grey disks enclosed by a hexagon. The icosahedral asymmetric unit contains 24 and one-third of these capsomers (numbered 1–25). Each trisymmetron contains 55 capsomers, all oriented similarly and rotated by 60° relative to those in the adjacent trisymmetron. Finger proteins bind to each trisymmetron (nine within one asymmetric unit are numbered in white), a total of 27 in each trisymmetron. A total of 18 Zip dimers are present at the interface between one trisymmetron and its adjacent trisymmetrons. Zip monomers are located at the interface between a trisymmetron and its neighbouring pentasymmetrons. The transmembrane anchor proteins (shown in Figure 2G) are located under capsomers 2 and 3 beneath the pentasymmetron.

(From Yan et al. (2009). J. Mol. Biol., 385, 1287–1299; with permission.)

Figure 4 Genomic structure of Ambystoma tigrinum virus (ATV). Arrows represent viral ORFs with their size, position and orientation shown. ORFs of known function are colored in red and their putative proteins identified; ORFs with known homology to tiger frog virus (TFV) are in blue; and those of unknown function or with no homology to TFV are indicated in black.

(From Jancovich et al. (2003). Virology, 316, 90–103; with permission.)

Figure 5 Replication cycle of frog virus 3 (FV-3).

(From Chinchar et al., (2002). Arch. Virol., 147, 447; with permission.)

Figure 6 Concatenated phylogeny of 26 conserved iridovirid sequences. Phylogenetic relationship of 26 conserved ORFs from the 14 completely sequenced iridovirid genomes. The neighbor-joining tree obtained using MEGA4 is shown with the statistical support indicating the robustness of the inferred branching pattern as assessed using the bootstrap test.

(Modified from Jancovich et al. (2010). J. Virol., 84, 2636–2647; with permission.)

Figure 7 A maximum-likelihood tree based on concatenated alignments (1849 positions) of five nucleocytoplasmic large DNA viruses (NCLDV) core proteins: D5 type ATPase, DNA polymerase B, A32 ATPase, major capsid protein and A1L/VLTF2 transcription factor. The tree was built using TreeFinder.

(From Boyer et al. (2009). PNAS, 106, 21848–21853; with permission.)