| 1. |
- De Souza, Joao, et al.
(författare)
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The complete nucleotide sequence of sweet potato C6 virus: a carlavirus lacking a cysteine-rich protein
- 2013
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Ingår i: Archives of Virology. - : Springer Science and Business Media LLC. - 0304-8608 .- 1432-8798. ; 158, s. 1393-1396
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Tidskriftsartikel (refereegranskat)abstract
- The complete nucleotide sequence of a sweet potato virus, first identified two decades ago as virus "C-6", was determined in this study. Sequence similarity and phylogenetic analysis clearly place it as a member of a distinct species within the genus Carlavirus, family Betaflexiviridae. Its genome structure was typical for that of other carlaviruses except that the ORF for the cysteine-rich protein was replaced by an ORF encoding a predicted protein with no similarity to any known protein.
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| 2. |
- Lukhovitskaya, Nina, et al.
(författare)
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A viral transcription factor exhibits antiviral RNA silencing suppression activity independent of its nuclear localization
- 2014
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Ingår i: Journal of General Virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 95, s. 2831-2837
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Tidskriftsartikel (refereegranskat)abstract
- Viral suppressors of RNA silencing (VSRs) are critical for the success of virus infection and efficient accumulation of virus progeny. The chrysanthemum virus B p12 protein acts as a transcription factor to regulate cell size and proliferation favourable for virus infection. Here, we showed that the p12 protein suppressed RNA silencing and was able to complement a VSR-deficient unrelated virus. Moreover, p12 counter-silencing activity could be uncoupled from its function as a transcription factor in the nucleus. The altered p12 protein, which lacked a nuclear localization signal and was not imported into the nucleus, was able to suppress RNA silencing as efficiently as the native protein. The data revealed new aspects of p12 functioning and identified a novel role for this viral zinc-finger transcription factor. The results provided a general insight into one of the activities of the p12 protein, which appeared to possess more than one function.
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| 3. |
- Lukhovitskaya, Nina, et al.
(författare)
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An RNA Virus-Encoded Zinc-Finger Protein Acts as a Plant Transcription Factor and Induces a Regulator of Cell Size and Proliferation in Two Tobacco Species
- 2013
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Ingår i: Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 25, s. 960-973
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Tidskriftsartikel (refereegranskat)abstract
- Plant viruses cause a variety of diseases in susceptible hosts. The disease symptoms often include leaf malformations and other developmental abnormalities, suggesting that viruses can affect plant development. However, little is known about the mechanisms underlying virus interference with plant morphogenesis. Here, we show that a C-4 type zinc-finger (ZF) protein, p12, encoded by a carlavirus (chrysanthemum virus B) can induce cell proliferation, which results in hyperplasia and severe leaf malformation. We demonstrate that the p12 protein activates expression of a regulator of cell size and proliferation, designated upp-L (upregulated by p12), which encodes a transcription factor of the basic/helix-loop-helix family sufficient to cause hyperplasia. The induction of upp-L requires translocation of the p12 protein into the nucleus and ZF-dependent specific interaction with the conserved regulatory region in the upp-L promoter. Our results establish the role of the p12 protein in modulation of host cell morphogenesis. It is likely that other members of the conserved C-4 type ZF family of viral proteins instigate reprogramming of plant development by mimicking eukaryotic transcriptional activators.
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| 4. |
- Lukhovitskaya, Nina, et al.
(författare)
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Deciphering the Mechanism of Defective Interfering RNA (DI RNA) Biogenesis Reveals That a Viral Protein and the DI RNA Act Antagonistically in Virus Infection
- 2013
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Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 87, s. 6091-6103
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Tidskriftsartikel (refereegranskat)abstract
- Potato mop-top virus (PMTV) produces a defective RNA (D RNA) encompassing the 5'-terminal 479 nucleotides (nt) and 3'-terminal 372 nt of RNA-TGB (where TGB is triple gene block). The mechanism that controls D RNA biogenesis and the role of D RNA in virus accumulation was investigated by introducing deletions, insertions, and point mutations into the sequences of the open reading frames (ORFs) of TGB1 and the 8-kilodalton (8K) protein that were identified as required for efficient production of the D RNA. Transient expression of RNA-TGB in the absence of RNA-Rep (which encodes the replicase) did not result in accumulation of D RNA, indicating that its production is dependent on PMTV replication. The D RNA could be eliminated by disrupting a predicted minus-strand stem-loop structure comprising complementary sequences of the 5' TGB1 ORF and the 3' 8K ORF, suggesting intramolecular template switching during positive-strand synthesis as a mechanism for the D RNA biogenesis. Virus accumulation was reduced when the 8K ORF was disrupted but D RNA was produced. Conversely, the virus accumulated at higher titers when the 8K ORF was intact and D RNA production was blocked. These data demonstrate that the D RNA interferes with virus infection and therefore should be referred to as a defective interfering RNA (DI RNA). The 8K protein was shown to be a weak silencing suppressor. This study provides an example of the interplay between a pathogen and its molecular parasite where virus accumulation was differentially regulated by the 8K protein and DI RNA, indicating that they play antagonistic roles and suggesting a mechanism by which the virus can attenuate replication, decreasing viral load and thereby enhancing its efficiency as a parasite.
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| 5. |
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| 6. |
- Lukhovitskaya, Nina, et al.
(författare)
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The N-Terminal Domain of PMTV TGB1 Movement Protein Is Required for Nucleolar Localization, Microtubule Association, and Long-Distance Movement
- 2010
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Ingår i: Molecular plant-microbe interactions. - 0894-0282 .- 1943-7706. ; 23, s. 1486-1497
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Tidskriftsartikel (refereegranskat)abstract
- The triple-gene-block (TGB)1 protein of Potato mop-top virus (PMTV) was fused to fluorescent proteins and expressed in epidermal cells of Nicotiana benthamiana under the control of the 35S promoter. TGB1 fluorescence was observed in the cytoplasm, nucleus, and nucleolus and occasionally associated with microtubules. When expressed from a modified virus (PMTV.YFP-TGB1) which formed local lesions but was not competent for systemic movement, yellow fluorescent protein (YFP)-TGB1 labeled plasmodesmata in cells at the leading edge of the lesion and plasmodesmata, microtubules, nuclei, and nucleoli in cells immediately behind the leading edge. Deletion of 84 amino acids from the N-terminus of unlabeled TGB1 within the PMTV genome abolished movement of viral RNA to non-inoculated leaves. When the same deletion was introduced into PMTV.YFP-TGB1, labeling of microtubules and nucleoli was abolished. The N-terminal 84 amino acids of TGB1 were fused to green fluorescent protein (GFP) and expressed in epidermal cells where GFP localized strongly to the nucleolus (not seen with unfused GFP), indicating that these amino acids contain a nucleolar localization signal; the fusion protein did not label microtubules. This is the first report of nucleolar and microtubule association of a TGB movement protein. The results suggest that PMTV TGB1 requires interaction with nuclear components and, possibly, microtubules for long-distance movement of viral RNA.
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| 7. |
- Lukhovitskaya, Nina, et al.
(författare)
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Unusual features of pomoviral RNA movement
- 2011
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 2
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Forskningsöversikt (refereegranskat)abstract
- Potato mop-top pomovirus (PMTV) is one of a few viruses that can move systemically in plants in the absence of the capsid protein (CP). Pomoviruses encode the triple gene block genetic module of movement proteins (TGB 1, 2, and 3) and recent research suggests that PMTV RNA is transported either as ribonucleoprotein (RNP) complexes containing TGB1 or encapsidated in virions containing TGB1. Furthermore, there are different requirements for local or systemic (long-distance) movement. Research suggests that nucleolar passage of TGB1 may be important for the long-distance movement of both RNP and virions. Moreover, and uniquely, the long-distance movement of the CP-encoding RNA requires expression of both major and minor CP subunits and is inhibited when only the major CP sub unit is expressed. This paper reviews pomovirus research and presents a current model for RNA movement.
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| 8. |
- Minina, Alyona, et al.
(författare)
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Autophagy and metacaspase determine the mode of cell death in plants
- 2013
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Ingår i: Journal of Cell Biology. - : Rockefeller University Press. - 0021-9525 .- 1540-8140. ; 203, s. 917-927
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Tidskriftsartikel (refereegranskat)abstract
- Although animals eliminate apoptotic cells using macrophages, plants use cell corpses throughout development and disassemble cells in a cell-autonomous manner by vacuolar cell death. During vacuolar cell death, lytic vacuoles gradually engulf and digest the cytoplasmic content. On the other hand, acute stress triggers an alternative cell death, necrosis, which is characterized by mitochondrial dysfunction, early rupture of the plasma membrane, and disordered cell disassembly. How both types of cell death are regulated remains obscure. In this paper, we show that vacuolar death in the embryo suspensor of Norway spruce requires autophagy. In turn, activation of autophagy lies downstream of metacaspase mcII-Pa, a key protease essential for suspensor cell death. Genetic suppression of the metacaspase-autophagy pathway induced a switch from vacuolar to necrotic death, resulting in failure of suspensor differentiation and embryonic arrest. Our results establish metacaspase-dependent autophagy as a bona fide mechanism that is responsible for cell disassembly during vacuolar cell death and for inhibition of necrosis.
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| 9. |
- Moschou, Panagiotis Nikolaou, et al.
(författare)
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The Caspase-Related Protease Separase (EXTRA SPINDLE POLES) Regulates Cell Polarity and Cytokinesis in Arabidopsis
- 2013
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Ingår i: Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 25, s. 2171-2186
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Tidskriftsartikel (refereegranskat)abstract
- Vesicle trafficking plays an important role in cell division, establishment of cell polarity, and translation of environmental cues to developmental responses. However, the molecular mechanisms regulating vesicle trafficking remain poorly understood. Here, we report that the evolutionarily conserved caspase-related protease separase (EXTRA SPINDLE POLES [ ESP]) is required for the establishment of cell polarity and cytokinesis in Arabidopsis thaliana. At the cellular level, separase colocalizes with microtubules and RabA2a (for RAS GENES FROM RAT BRAINA2a) GTPase-positive structures. Separase facilitates polar targeting of the auxin efflux carrier PIN-FORMED2 (PIN2) to the rootward side of the root cortex cells. Plants with the radially swollen4 (rsw4) allele with compromised separase activity, in addition to mitotic failure, display isotropic cell growth, perturbation of auxin gradient formation, slower gravitropic response in roots, and cytokinetic failure. Measurements of the dynamics of vesicle markers on the cell plate revealed an overall reduction of the delivery rates of KNOLLE and RabA2a GTPase in separase-deficient roots. Furthermore, dissociation of the clathrin light chain, a protein that plays major role in the formation of coated vesicles, was slower in rsw4 than in the control. Our results demonstrate that separase is a key regulator of vesicle trafficking, which is indispensable for cytokinesis and the establishment of cell polarity.
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| 10. |
- Ramesh, Vetukuri, et al.
(författare)
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Evidence for involvement of Dicer-like, Argonaute and histone deacetylase proteins in gene silencing in Phytophthora infestans
- 2011
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Ingår i: Molecular Plant Pathology. - 1464-6722 .- 1364-3703. ; 12, s. 772-785
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Tidskriftsartikel (refereegranskat)abstract
- Gene silencing may have a direct or indirect impact on many biological processes in eukaryotic cells, and is a useful tool for the determination of the roles of specific genes. In this article, we report silencing in Phytophthora infestans, an oomycete pathogen of potato and tomato. Gene silencing is known to occur in P. infestans, but its genetic basis has yet to be determined. Genes encoding the major components of the RNA interference (RNAi) pathway, Dicer-like (Pidcl1), Argonaute (Piago1-5) and RNA-directed RNA polymerase (Pirdr1), were identified in the P. infestans genome by comparative genomics, together with families of other genes potentially involved in gene silencing, such as histone deacetylases, histone methyltransferases, DEAD heli-cases, chromodomain proteins and a class 1 RNaseIII. Real-time reverse transcription-polymerase chain reaction demonstrated transcript accumulation for all candidate genes throughout the asexual lifecycle and plant infection, but at different levels of mRNA abundance. A functional assay was developed in which silencing of the sporulation-associated Picdc14 gene was released by the treatment of protoplasts with in vitro-synthesized double-stranded RNAs homologous to Pidcl1, Piago1/2 and histone deacetylase Pihda1. These results suggest that the components of gene silencing, namely Dicer-like, Argonaute and histone deacetylase, are functional in P. infestans. Our data demonstrate that this oomycete possesses canonical gene silencing pathways similar to those of other eukaryotes.
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