Comparative Ultrastructural Observations of Plasmalemmasomes in PSTVd‐Infected Healthy and Artificially Stunted Tomato Leaves

Gruner, Reinhard; Santore, Uwe J.

doi:10.1111/j.1439-0434.1991.tb01194.x

Cited by 5 publications

(3 citation statements)

References 24 publications

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“…Anomalies in cell wall structures are also consistent with: (i) modifications in wall composition of CEVd-infected tomato cells with respect to their healthy counterparts (Wang et al, 1986), and (ii) a marked reduction in the number of protoplasts, released from CEVd-containing tomato tissues and non-differentiated calli treated with enzymes for disrupting cell walls, with respect to healthy controls (Marton et al, 1982). However, no clear differences between the cell walls of healthy and PSTVd-infected tomato leaves were observed by Gruner and Santore (1991). …”

Section: Viroid Infection Is Frequently Accompanied By Cytological Almentioning

confidence: 81%

“…On the other hand, Marton et al (1982) observed in CEVd-infected tomato callus cells a significantly higher frequency of PSs that was not regarded as viroid-specific but rather a secondary (and non-specific) effect of viroid infection. Similarly, the higher number of PSs detected by Gruner and Santore (1991) in PSTVd-infected tomato leaves with respect to healthy controls was considered as a non-specific physiological response to diverse abiotic and biotic stresses. Interestingly, an increase in the number and size of paramural bodies with respect to healthy controls was also reported in ASBVd-infected avocado tissues (Figure 1B; Da Graça and Martin, 1981), thus showing that alterations in PSs are not restricted to infections by nuclear-replicating viroids.…”

Section: Viroid Infection Is Frequently Accompanied By Cytological Almentioning

confidence: 99%

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Cytopathic Effects Incited by Viroid RNAs and Putative Underlying Mechanisms

Serio¹,

Stradis²,

Delgado³

et al. 2013

Front. Plant Sci.

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Viroids are infectious agents identified only in plants so far. In contrast to viruses, the genome of viroids is composed of a tiny circular RNA (250–400 nt) not coding for proteins, but containing in its compact structure all the information needed for parasitizing the transcriptional and RNA trafficking machineries of their hosts. Viroid infections are frequently accompanied by cellular and developmental disorders that ultimately result in macroscopic symptoms. The molecular events linking the structural domains of viroid RNAs with cellular and macroscopic alterations remain largely unexplored, although significant progress has been lately achieved in one specific viroid-host combination, highlighting the ability of viroids to strongly interfere with their host RNA regulatory networks. Cytopathic effects induced by nuclear-replicating viroids, which were investigated since early studies on viroids, consist in irregular proliferations of cell membranes (paramural bodies or plasmalemmasomes), cell wall distortions, and chloroplast malformations. Different alternatives have been proposed regarding how these cytological alterations may influence the onset of macroscopic symptoms. Recently, the cytopathology and histopathology incited by a chloroplast-replicating viroid have been investigated in depth, with defects in chloroplast development having been related to specific molecular events that involve RNA silencing and impairment of chloroplast ribosomal RNA maturation. On this basis, a tentative model connecting specific cytopathologic alterations with symptoms has been put forward. Here, early and more recent studies addressing this issue will be reviewed and reassessed in the light of recent advances in the regulatory roles of small RNAs.

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Section: Viroid Infection Is Frequently Accompanied By Cytological Almentioning

confidence: 81%

Section: Viroid Infection Is Frequently Accompanied By Cytological Almentioning

confidence: 99%

Cytopathic Effects Incited by Viroid RNAs and Putative Underlying Mechanisms

Serio¹,

Stradis²,

Delgado³

et al. 2013

Front. Plant Sci.

View full text Add to dashboard Cite

show abstract

“…The specific localization of viroids by microscopy at the ultrastructural level has so far been limited to examination of viroid-associated symptoms, such as plasmalemmasomes (Marton et aL, 1982;Semancik and Vanderwoude, 1976), and other membrane-associated vesicles (Gruner and Santore, 1991 ) and to fluorescence in situ hybridization studies done on preparations of isolated, purified nuclei using confocal laser microscopy (Harders et aL, 1989).…”

Section: Discussionmentioning

confidence: 99%

In situ hybridization localizes avocado sunblotch viroid on chloroplast thylakoid membranes and coconut cadang cadang viroid in the nucleus

1994

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SummaryViroids, small single-stranded circular RNA molecules, are the smallest known infectious agents in Nature. The apparent Inability of viroids to encode for proteins means that they must rely fully on host functione for their replication. The specific ultrastructural localization of viroids is fundamental to the determination of their replication strategies. In this paper the first in situ hybridization study to localize viroids within the cell at the electron microscope level is reported. Biotin-labelled RNA probes were used with subsequent detection by gold-labelled monoclonal anti-biotin antibodies to localize avocado sunblotch viroid and coconut cadang cadang viroid. Avocado sunblotch viroid was located in chloroplasts, mostly on the thylakoid membranes of cells from Infected leaves of avocado (Parsee americana). In contrast, coconut cadang cadang viroid was located in the nucleolus and nucleoplasm of cells of infected leaves of oil palm (Elaeis guineensis), with a higher concentration in the nucleolus. The results provide insight on the potential host RNA polymerases involved in the replication of these two viroids.

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Unconventional protein secretion in plants: a critical assessment

2015

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Unconventional protein secretion (UPS) is a collective term for mechanisms by which cytosolic proteins that lack a signal peptide ("leaderless secretory proteins" (LSPs)) can gain access to the cell exterior. Numerous examples of UPS have been well documented in animal and yeast cells. In contrast, our understanding of the mechanism(s) and function of UPS in plants is very limited. This review evaluates the available literature on this subject. The apparent large numbers of LSPs in the plant secretome suggest that UPS also occurs in plants but is not a proof. Although the direct transport of LSPs across the plant plasma membrane (PM) has not yet been described, it is possible that as in other eukaryotes, exosomes may be released from plant cells through fusion of multivesicular bodies (MVBs) with the PM. In this way, LSPs, but also small RNAs (sRNAs), that are passively taken up from the cytosol into the intraluminal vesicles of MVBs, could reach the apoplast. Another possible mechanism is the recently discovered exocyst-positive organelle (EXPO), a double-membrane-bound compartment, distinct from autophagosomes, which appears to sequester LSPs.

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Comparative Ultrastructural Observations of Plasmalemmasomes in PSTVd‐Infected Healthy and Artificially Stunted Tomato Leaves

Cited by 5 publications

References 24 publications

Cytopathic Effects Incited by Viroid RNAs and Putative Underlying Mechanisms

Cytopathic Effects Incited by Viroid RNAs and Putative Underlying Mechanisms

In situ hybridization localizes avocado sunblotch viroid on chloroplast thylakoid membranes and coconut cadang cadang viroid in the nucleus

Unconventional protein secretion in plants: a critical assessment

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