CYTOPATHIC FEATURES INDUCED BY CALADIUM VIRUS X (POTEXVIRUS) IN CALADIUM BICOLOR AND GOMPHRENA GLOBOSA

Dasheen mosaic virus (DsMV), a Potyvirus, and a Potexvirus (herein tentatively named Caladium virus X, CalVX) were found naturally infecting Caladium bicolor (Araceae) with chlorotic and necrotic spots and rings. Electron microscopy observations from infected leaves revealed cytoplasmic cylindrical inclusions, induced by DsMV, as well as masses of elongated particles and virus-like particles scattered in the cytoplasm. In Gomphrena globosa foliar cells experimentally infected by CalVX, electron-dense crystalline inclusions, without elongated particles, were also present in the cytoplasm and nucleus. Complex inclusions which consisted of a central, stained faint yellow area surrounded by groups of dense, olive-green stained, bodies were frequently observed in epidermal cells when stained with calcomine orange-luxol brilliant green combination. These inclusions correspond to a cytoplasm region rich in vesicles, ribosomes, scattered virus-like particles and large virus aggregates.

KEY WORDS:
Caladium bicolor; Araceae; Potexvirus; cytopathic alterations; electron microscopy; light microscopy.

Authorship

E.B. Rivas

Instituto Biológico, Centro de Pesquisa e Desenvolvimento de Sanidade Vegetal, Av. Cons. Rodrigues Alves, 1252, 04014-002, São Paulo, SP, BrasilInstituto BiológicoBrasilSão Paulo, SP, BrasilInstituto Biológico, Centro de Pesquisa e Desenvolvimento de Sanidade Vegetal, Av. Cons. Rodrigues Alves, 1252, 04014-002, São Paulo, SP, Brasil

S.R. Galleti

L.M.L. Duarte

M.A.V. Alexandre

M.E.M. Estelita

Universidade de São Paulo, Instituto de Biociências, São Paulo, SP, BrasilUniversidade de São PauloBrasilSão Paulo, SP, BrasilUniversidade de São Paulo, Instituto de Biociências, São Paulo, SP, Brasil

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Figures

Figures (8)

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Fig. 1
Caladium bicolor, naturally infected by Dasheen mosaic virus and Caladium virus X, showing chlorotic spots and rings, and necrotic rings.

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Fig. 2
Gomphrena globosa, experimentally infected by Caladium virus X, showing necrotic, red halo-surrounded spots 14 day after inoculation.

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Fig. 3
Thin sections of palisade cells of Caladium bicolor naturally infected by DsMV and CalVX. A- Transversally (T) and longitudinally (L) cylindrical inclusions, close to organelles and virus-like particles (P) in the cytoplasm containing, in sections. B- Fibrous mass (Fm) in a cytoplasmic region rich in double membrane vesicles (Vd) and membranous tubules (Mt). C- Viruslike particles scattered in the cytoplasm showing intumescent endoplasmic reticulum (Er); vesicles with double membrane (Vd) can be observed between cytoplasmatic membrane and cell wall. Ch- chloroplast, O- osmiophilic globule, Pe- peroxisome, Rerough endoplasmic reticulum, Ve- vesicles with electron-dense contents, W- cell wall. Bars = 200 nm.

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Fig. 4
Plasmodesmata between Caladium bicolor infected mesophyll cells. A- Plasmodesmata with protruding plasmatubules (Pt); vesicles with double membrane or desmotubules in transversal sections (Vd). B- Dilated plasmadesmata containing electron-dense globules (G) in which desmotubules could be occasionally observed. W- cell wall. Bars = 200 nm.

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Fig. 5
Unusual aspects observed in Caladium bicolor cytoplasm mesophyll cells. A- Rounded osmiophilic bodies imersed in electron-dense mass, containing or not crystalline inclusion (CI). Bar = 1470 nm. B- Amorphous X-bodies composed by granular (Go) and fibrous (Fo) osmiophilic bodies. C- Elongated structure (Es) close to organelles: chloroplast (Ch), dictyosome (D), mitochondrion (M), and peroxisome containing a crystal (Cr). D- Detail of the elongated structure showing its regular internal organization with reticulate (R) and parallel (Pa) array; note a membrane surrounding the structure (arrow-head). Bars = 200 nm.

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Fig. 6
Electron-dense, crystalline inclusions (I), apparently involved by a membrane (arrowhead) in mesophyll cells of Gomphrena globosa infected by CalVX. A- Inclusion probably located in a protruding cytoplasm in the nucleus (N). B- Inclusion in the cytoplasm. Ch- chloroplast. W- cell wall. Bars = 500 nm.

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Fig. 7
Mesophyll cells of CalVX infected Gomphrena globosa. A- Vesicles (Vg) with granular contents in the cytoplasm close to cell wall. B- Vesicular bodies (Vb) and filamentous bodies (Fb) between cytoplasmic membrane and cell wall. D- dictyosome, N- nucleus, W- cell wall. Bars = 600 nm.

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Fig. 8
Light microscope micrography of paradermal sections of Gomphrena globosa infected by CalVX. A- Granular and dense region (I) of cytoplasm stained with Calcomine orange - Luxol brilliant green. B- Detail of delimited area in A. C-Banded inclusion (I) imersed in granular and dense region (Rd) of cytoplasm stained with Azure A. N- nucleus, Pl- plastids. Bars = 10 µm.

Fig. 1 Caladium bicolor, naturally infected by Dasheen mosaic virus and Caladium virus X, showing chlorotic spots and rings, and necrotic rings.

Fig. 2 Gomphrena globosa, experimentally infected by Caladium virus X, showing necrotic, red halo-surrounded spots 14 day after inoculation.

Fig. 3 Thin sections of palisade cells of Caladium bicolor naturally infected by DsMV and CalVX. A- Transversally (T) and longitudinally (L) cylindrical inclusions, close to organelles and virus-like particles (P) in the cytoplasm containing, in sections. B- Fibrous mass (Fm) in a cytoplasmic region rich in double membrane vesicles (Vd) and membranous tubules (Mt). C- Viruslike particles scattered in the cytoplasm showing intumescent endoplasmic reticulum (Er); vesicles with double membrane (Vd) can be observed between cytoplasmatic membrane and cell wall. Ch- chloroplast, O- osmiophilic globule, Pe- peroxisome, Rerough endoplasmic reticulum, Ve- vesicles with electron-dense contents, W- cell wall. Bars = 200 nm.

Fig. 4 Plasmodesmata between Caladium bicolor infected mesophyll cells. A- Plasmodesmata with protruding plasmatubules (Pt); vesicles with double membrane or desmotubules in transversal sections (Vd). B- Dilated plasmadesmata containing electron-dense globules (G) in which desmotubules could be occasionally observed. W- cell wall. Bars = 200 nm.

Fig. 5 Unusual aspects observed in Caladium bicolor cytoplasm mesophyll cells. A- Rounded osmiophilic bodies imersed in electron-dense mass, containing or not crystalline inclusion (CI). Bar = 1470 nm. B- Amorphous X-bodies composed by granular (Go) and fibrous (Fo) osmiophilic bodies. C- Elongated structure (Es) close to organelles: chloroplast (Ch), dictyosome (D), mitochondrion (M), and peroxisome containing a crystal (Cr). D- Detail of the elongated structure showing its regular internal organization with reticulate (R) and parallel (Pa) array; note a membrane surrounding the structure (arrow-head). Bars = 200 nm.

Fig. 6 Electron-dense, crystalline inclusions (I), apparently involved by a membrane (arrowhead) in mesophyll cells of Gomphrena globosa infected by CalVX. A- Inclusion probably located in a protruding cytoplasm in the nucleus (N). B- Inclusion in the cytoplasm. Ch- chloroplast. W- cell wall. Bars = 500 nm.

Fig. 7 Mesophyll cells of CalVX infected Gomphrena globosa. A- Vesicles (Vg) with granular contents in the cytoplasm close to cell wall. B- Vesicular bodies (Vb) and filamentous bodies (Fb) between cytoplasmic membrane and cell wall. D- dictyosome, N- nucleus, W- cell wall. Bars = 600 nm.

Fig. 8 Light microscope micrography of paradermal sections of Gomphrena globosa infected by CalVX. A- Granular and dense region (I) of cytoplasm stained with Calcomine orange - Luxol brilliant green. B- Detail of delimited area in A. C-Banded inclusion (I) imersed in granular and dense region (Rd) of cytoplasm stained with Azure A. N- nucleus, Pl- plastids. Bars = 10 µm.

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CYTOPATHIC FEATURES INDUCED BY CALADIUM VIRUS X (POTEXVIRUS) IN CALADIUM BICOLOR AND GOMPHRENA GLOBOSA

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