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Genetic and histological studies on the delayed systemic movement of Tobacco Mosaic Virus in Arabidopsis thaliana.

Serrano C, González-Cruz J, Jauregui F, Medina C, Mancilla P, Matus JT, Arce-Johnson P - BMC Genet. (2008)

Bottom Line: Electron microscopy studies following the virion's route in stems of Col-0 infected plants showed the presence of curved structures, instead of the typical rigid rods of TMV-U1.This was not observed in the case of TMV-U1 infection in Uk-4, where the observed virions have the typical rigid rod morphology.The presence of defectively assembled virions observed by electron microscopy in vascular tissue of Col-0 infected plants correlates with a recessive delayed systemic movement trait of TMV-U1 in this ecotype.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Casilla 114-D. Santiago, Chile. clserran@puc.cl

ABSTRACT

Background: Viral infections and their spread throughout a plant require numerous interactions between the host and the virus. While new functions of viral proteins involved in these processes have been revealed, current knowledge of host factors involved in the spread of a viral infection is still insufficient. In Arabidopsis thaliana, different ecotypes present varying susceptibilities to Tobacco mosaic virus strain U1 (TMV-U1). The rate of TMV-U1 systemic movement is delayed in ecotype Col-0 when compared with other 13 ecotypes.We followed viral movement through vascular tissue in Col-0 plants by electronic microscopy studies. In addition, the delay in systemic movement of TMV-U1 was genetically studied.

Results: TMV-U1 reaches apical leaves only after 18 days post rosette inoculation (dpi) in Col-0, whereas it is detected at 9 dpi in the Uk-4 ecotype. Genetic crosses between Col-0 and Uk-4 ecotypes, followed by analysis of viral movement in F1 and F2 populations, revealed that this delayed movement correlates with a recessive, monogenic and nuclear locus. The use of selected polymorphic markers showed that this locus, denoted DSTM1 (Delayed Systemic Tobamovirus Movement 1), is positioned on the large arm of chromosome II. Electron microscopy studies following the virion's route in stems of Col-0 infected plants showed the presence of curved structures, instead of the typical rigid rods of TMV-U1. This was not observed in the case of TMV-U1 infection in Uk-4, where the observed virions have the typical rigid rod morphology.

Conclusion: The presence of defectively assembled virions observed by electron microscopy in vascular tissue of Col-0 infected plants correlates with a recessive delayed systemic movement trait of TMV-U1 in this ecotype.

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Curved TMV-U1 virions accumulate in the vascular tissues of infected Col-0 plants. Electron microscopy images of virus infected tissues in Col-0 and Uk-4 plants were taken at 18 dpi. Curved virions are evident in the vascular tissue of the stem (a) and petiole of apical leaves (b), but normal rigid rod virions appear in the mesophyll of apical leaves (c). Rigid rod virions appear in the stem (d) and petiole of apical leaves (e) in Uk-4 plants. An image of Col-0 vascular cells infected with the TMV-Cg strain was included as a control (f). Bars: 100 μm.
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Figure 3: Curved TMV-U1 virions accumulate in the vascular tissues of infected Col-0 plants. Electron microscopy images of virus infected tissues in Col-0 and Uk-4 plants were taken at 18 dpi. Curved virions are evident in the vascular tissue of the stem (a) and petiole of apical leaves (b), but normal rigid rod virions appear in the mesophyll of apical leaves (c). Rigid rod virions appear in the stem (d) and petiole of apical leaves (e) in Uk-4 plants. An image of Col-0 vascular cells infected with the TMV-Cg strain was included as a control (f). Bars: 100 μm.

Mentions: Since the virus is detected in Col-0 apical tissues only after 18 dpi (Figure 1c) [16], cross sections of the vascular zone of rosette leaves, stems and apical leaves were studied at this time point. Surprisingly, curved virions, similar in length to the rigid viral rods (300 nm) were observed in the vascular tissue of the stem (Figure 3a) and in apical leaf petioles (3b). Similar structures were observed in the stems of Col-0 plants in three independent experiments. These could correspond to defectively assembled virions or different associations of viral proteins. However, in the mesophyll cells of apical leaves, normal rigid rods of TMV-U1 were observed (Figure 3c). On the other hand, in the case of Uk-4 infected plants, the stem (3d) and the apical leaf petioles (3e) harboured rigid viral rods. To evaluate if the curved virions appeared when different Tobamoviruses infect Col-0 plants, the crucifer infecting TMV-Cg was tested. TMV-Cg efficiently infects several Arabidopsis ecotypes and in this case normal shaped virions were always found in the vascular tissue of rosette leaves, stems and apical leaves (Figure 3f).


Genetic and histological studies on the delayed systemic movement of Tobacco Mosaic Virus in Arabidopsis thaliana.

Serrano C, González-Cruz J, Jauregui F, Medina C, Mancilla P, Matus JT, Arce-Johnson P - BMC Genet. (2008)

Curved TMV-U1 virions accumulate in the vascular tissues of infected Col-0 plants. Electron microscopy images of virus infected tissues in Col-0 and Uk-4 plants were taken at 18 dpi. Curved virions are evident in the vascular tissue of the stem (a) and petiole of apical leaves (b), but normal rigid rod virions appear in the mesophyll of apical leaves (c). Rigid rod virions appear in the stem (d) and petiole of apical leaves (e) in Uk-4 plants. An image of Col-0 vascular cells infected with the TMV-Cg strain was included as a control (f). Bars: 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2563018&req=5

Figure 3: Curved TMV-U1 virions accumulate in the vascular tissues of infected Col-0 plants. Electron microscopy images of virus infected tissues in Col-0 and Uk-4 plants were taken at 18 dpi. Curved virions are evident in the vascular tissue of the stem (a) and petiole of apical leaves (b), but normal rigid rod virions appear in the mesophyll of apical leaves (c). Rigid rod virions appear in the stem (d) and petiole of apical leaves (e) in Uk-4 plants. An image of Col-0 vascular cells infected with the TMV-Cg strain was included as a control (f). Bars: 100 μm.
Mentions: Since the virus is detected in Col-0 apical tissues only after 18 dpi (Figure 1c) [16], cross sections of the vascular zone of rosette leaves, stems and apical leaves were studied at this time point. Surprisingly, curved virions, similar in length to the rigid viral rods (300 nm) were observed in the vascular tissue of the stem (Figure 3a) and in apical leaf petioles (3b). Similar structures were observed in the stems of Col-0 plants in three independent experiments. These could correspond to defectively assembled virions or different associations of viral proteins. However, in the mesophyll cells of apical leaves, normal rigid rods of TMV-U1 were observed (Figure 3c). On the other hand, in the case of Uk-4 infected plants, the stem (3d) and the apical leaf petioles (3e) harboured rigid viral rods. To evaluate if the curved virions appeared when different Tobamoviruses infect Col-0 plants, the crucifer infecting TMV-Cg was tested. TMV-Cg efficiently infects several Arabidopsis ecotypes and in this case normal shaped virions were always found in the vascular tissue of rosette leaves, stems and apical leaves (Figure 3f).

Bottom Line: Electron microscopy studies following the virion's route in stems of Col-0 infected plants showed the presence of curved structures, instead of the typical rigid rods of TMV-U1.This was not observed in the case of TMV-U1 infection in Uk-4, where the observed virions have the typical rigid rod morphology.The presence of defectively assembled virions observed by electron microscopy in vascular tissue of Col-0 infected plants correlates with a recessive delayed systemic movement trait of TMV-U1 in this ecotype.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Casilla 114-D. Santiago, Chile. clserran@puc.cl

ABSTRACT

Background: Viral infections and their spread throughout a plant require numerous interactions between the host and the virus. While new functions of viral proteins involved in these processes have been revealed, current knowledge of host factors involved in the spread of a viral infection is still insufficient. In Arabidopsis thaliana, different ecotypes present varying susceptibilities to Tobacco mosaic virus strain U1 (TMV-U1). The rate of TMV-U1 systemic movement is delayed in ecotype Col-0 when compared with other 13 ecotypes.We followed viral movement through vascular tissue in Col-0 plants by electronic microscopy studies. In addition, the delay in systemic movement of TMV-U1 was genetically studied.

Results: TMV-U1 reaches apical leaves only after 18 days post rosette inoculation (dpi) in Col-0, whereas it is detected at 9 dpi in the Uk-4 ecotype. Genetic crosses between Col-0 and Uk-4 ecotypes, followed by analysis of viral movement in F1 and F2 populations, revealed that this delayed movement correlates with a recessive, monogenic and nuclear locus. The use of selected polymorphic markers showed that this locus, denoted DSTM1 (Delayed Systemic Tobamovirus Movement 1), is positioned on the large arm of chromosome II. Electron microscopy studies following the virion's route in stems of Col-0 infected plants showed the presence of curved structures, instead of the typical rigid rods of TMV-U1. This was not observed in the case of TMV-U1 infection in Uk-4, where the observed virions have the typical rigid rod morphology.

Conclusion: The presence of defectively assembled virions observed by electron microscopy in vascular tissue of Col-0 infected plants correlates with a recessive delayed systemic movement trait of TMV-U1 in this ecotype.

Show MeSH
Related in: MedlinePlus