Nuclear Ultrastructural Changes and Aggregates of Viruslike Particles in Mungbean Cells Affected by Mungbean Yellow Mosaic Disease

Indian Cassava Mosaic Virus: Ultrastructure of Infected Cells

“…Although the occurrence of tubular aggregates, crystalline sheets and ordered rows appears to be characteristic of the respective virus infections, absence of these structures in ICMV-infected cells may be due to the fixation procedure because the formation of virus crystals can occur in cells which are water-stressed (Milne, 1967;Hatta & Matthews, 1974), although this was considered to be unlikely for CSMV (Francki et al, 1979). Fibrillar ring structures (Kim et al, 1978;Kim & Flores, 1979) were regularly found in ICMVinfected leaf tissue and appear similar to those found for other whitefly-transmitted geminiviruses (Kim et al, 1978;Horvat & Verhoyen, 1981 ;Thongmeearkom et al, 1981 ;Kim & Fulton, 1984). Their role in infection is unclear.…”

“…In some cells, nuclei could be found with peripheral chromatin but no viral inclusions and such nuclei sometimes contained the second type of inclusion, fibrillar rings (Fig. 9), which resembled those found in cells infected with other whitefly-transmitted geminiviruses (Kim & Flores, 1979;Thongmeearkom et al, 1981;Kim et al, 1986;Rushing et al, 1987). Examination of serial sections of the fibrillar rings showed that they represent hollow spheres.…”

“…Inclusions of virus particles similar to those seen in ICMV-infected leaves are found in leaves infected with beet curly top (BCTV) (Esau, 1977;Esau & Magyarosy, 1979), Venezuelan tomato yellow mosaic (Lastra & Gil, 1981), euphorbia mosaic (EuMV) (Kim & Flores, 1979;Kim & Fulton, 1984), bean golden mosaic (BGMV) (Kim et al, 1978), ACMV (Horvat & Verhoyen, 1981 ;Adejare & Coutts, 1982), jatropha mosaic (JMV) (Kim et aL, 1986), chloris striate mosaic (CSMV) (Francki et al, 1979), tomato yellow leaf curl (Russo et al, 1980) and mungbean yellow mosaic (MYMV) (Thongmeearkom et al, 1981) geminiviruses. ICMV particles, however, were always seen as irregularly shaped inclusions, and were never found in tubular arrays as exhibited by abutilon mosaic virus (Jeske et al, 1977;Jeske & Schuchalter-Eicke, 1984) or MYMV (Thongmeearkom et al, 1981), nor as crystalline sheets of virus particles as seen with tomato golden mosaic virus (Rushing et al, 1987), BGMV (Kim et al, 1978) or maize streak virus (Bock, 1974). Ordered rows or rod-like aggregates of virus particles similar to those seen with tomato leaf curl virus (Osaki & Inouye, 1978), CSMV (Francki et al, 1979) or BCTV in spinach (Esau, 1977) were never seen.…”

Geminiviruses

“…Vector relationships are probably of little use in classifying candidate viruses since numerous other viruses and prokaryotes are leafhopper transmitted, some by the same species that also transmit a geminivirus, and two filamentous viruses have been reported to be transmitted by B. tabaci (Hollings & Stone, 1976;Sela et al, 1980). Some geminiviruses cause distinctive cytological effects in the nuclei of infected cells that have been useful in anticipating affinity of new viruses with the group (Kim et al, 1978;Kim & Flores, 1979;Osaki et al, 1979;Thongmeearkom et al, 1981). Present evidence suggests that the presence of such cytopathology is diagnostic but that its absence is not.…”

“…The unique capsid morphology, and in some cases the unusual cytological features of geminivirus infections (Kim et al, 1978;Kim & Flores, 1979;Osaki et al, 1979;Thongmeearkom et al, 1981;Russo et al, 1980), however, are sufficiently distinctive that it is possible to tentatively assign certain other viruses to the group. The viruses for which some evidence exists for geminivirus affinities are listed in Table 1 together with a summary of the properties on which the assignment was made.…”