A Geminivirus Induces Expression of a Host DNA Synthesis Protein in Terminally Differentiated Plant Cells

Nagar, Steven; Pedersen, Thomas J.; Carrick, Kevin M.; Hanley‐Bowdoin, Linda; Robertson, Dominique

doi:10.2307/3870173

Cited by 27 publications

(55 citation statements)

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“…Similarities between interactions of the RepA protein with plant cell proteins (5,9,11,13) and the resultant subversion of host cell cycle machinery led various researchers to suggest a similarity between plant geminiviruses and mammalian oncoviruses (8,9,12,13,18,35). We can now expand these similarities to RepA-mediated stimulation of the cell cycle in BY-2 cells and callus growth in maize, observations consistent with the stimulation of cell proliferation associated with oncoviral infection (15)(16)(17).…”

Section: Discussionsupporting

confidence: 55%

“…Consistent with the two proteins having different effects on plant growth, Nos:RepA expression, but not Nos:Rep, resulted in increased maize transformation. As others have not observed cell cycle stimulation (1,2,10,18,(47)(48)(49)(50), there may be restricted cell-or tissue-type responsiveness to RepA. Other cell-type-specific responses to geminiviral Rep expression and replication were reported for wheat suspension cultures and scutellar cells (47).…”

Section: Discussionmentioning

confidence: 97%

“…Immunochemical analysis of geminivirus-infected plant cells has identified a stimulation of replication-associated machinery. In terminally differentiated tobacco leaf cells, Rep expression or infection with tomato golden mosaic virus are associated with increases in proliferating cell nuclear antigen (18), an integral component of DNA polymerase regulated by E2F-binding sites in both animals and plants (19). Surprisingly, despite their interactions with Rb and activation of replication machinery, cell proliferation as a result of Rep or RepA expression has not been reported for plant cells.…”

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confidence: 97%

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Stimulation of the cell cycle and maize transformation by disruption of the plant retinoblastoma pathway

Gordon‐Kamm

Dilkes

Lowe

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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The genome of the Mastreviruses encodes a replication-associated protein (RepA) that interacts with members of the plant retinoblastoma-related protein family, which are putative cell cycle regulators. Expression of ZmRb1, a maize retinoblastoma-related gene, and RepA inhibited and stimulated, respectively, cell division in tobacco cell cultures. The effect of RepA was mitigated by over-expression of ZmRb1. RepA increased transformation frequency and callus growth rate of high type II maize germplasm. RepA-containing transgenic maize calli remained embryogenic, were readily regenerable, and produced fertile plants that transmitted transgene expression in a Mendelian fashion. In high type II, transformation frequency increased with the strength of the promoter driving RepA expression. When a construct in which RepA was expressed behind its native LIR promoter was used, primary transformation frequencies did not improve for two elite Pioneer maize inbreds. However, when LIR:RepA-containing transgenic embryos were used in subsequent rounds of transformation, frequencies were higher in the RepA؉ embryos. These data demonstrate that RepA can stimulate cell division and callus growth in culture, and improve maize transformation.

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Section: Discussionsupporting

confidence: 55%

Section: Discussionmentioning

confidence: 97%

mentioning

confidence: 97%

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Stimulation of the cell cycle and maize transformation by disruption of the plant retinoblastoma pathway

Gordon‐Kamm

Dilkes

Lowe

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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“…AL1 is necessary for replication, whereas AL3 enhances viral DNA accumulation by an unknown mechanism (15,16) (AL1 homologues are also designated C1 or Rep.) AL1 is a multifunctional protein that mediates both virus-specific recognition of its cognate origin (17) and transcriptional repression by binding to the directly repeated sequence in the intergenic region (10,12). AL1 initiates and terminates plus strand replication (13,14,18) and induces the accumulation of a host replication factor, proliferating cell nuclear antigen, in infected cells (19). Recombinant AL1 specifically binds double-stranded DNA (11,20), cleaves and ligates single-stranded DNA in the invariant sequence of the hairpin loop (14,21), and hydrolyzes ATP (22,23).…”

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confidence: 99%

The Multifunctional Character of a Geminivirus Replication Protein Is Reflected by Its Complex Oligomerization Properties

Orozco

Kong

Batts

et al. 2000

Journal of Biological Chemistry

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Tomato golden mosaic virus (TGMV), a member of the geminivirus family, encodes one essential replication protein, AL1, and recruits the rest of the DNA replication apparatus from its plant host. TGMV AL1 is an oligomeric protein that binds double-stranded DNA and catalyzes cleavage and ligation of single-stranded DNA. The oligomerization domain, which is required for DNA binding, maps to a region that displays strong sequence and structural homology to other geminivirus Rep proteins. To assess the importance of conserved residues, we generated a series of site-directed mutations and analyzed their impact on AL1 function in vitro and in vivo. Two-hybrid experiments revealed that mutation of amino acids 157-159 inhibited AL1-AL1 interactions, whereas mutations at nearby residues reduced complex stability. Changes at positions 157-159 also disrupted interaction between the full-length mutant protein and a glutathione S-transferase-AL1 oligomerization domain fusion in insect cells. The mutations had no detectable effect on oligomerization when both proteins contained full-length AL1 sequences, indicating that AL1 complexes can be stabilized by amino acids outside of the oligomerization domain. Nearly all of the oligomerization domain mutants were inhibited or severely attenuated in their ability to support AL1-directed viral DNA replication. In contrast, the same mutants were enhanced for AL1-mediated transcriptional repression. The replication-defective AL1 mutants also interfered with replication of a TGMV A DNA encoding wild type AL1. Full-length mutant AL1 was more effective in the interference assays than truncated proteins containing the oligomerization domain. Together, these results suggested that different AL1 complexes mediate viral replication and transcriptional regulation and that replication interference involves multiple domains of the AL1 protein.Geminiviruses are a large family of plant viruses with circular, single-stranded DNA genomes that replicate in the nuclei of infected cells (reviewed in Ref. 1). The single-stranded genome is converted to a double-stranded DNA that serves as the template for rolling circle replication (2-4) and transcription (5, 6). Geminiviruses do not encode their own polymerases and, instead, rely on host enzymes for viral DNA and RNA synthesis. These characteristics make geminiviruses excellent model systems for studying plant DNA replication and transcription mechanisms.The geminivirus, tomato golden mosaic virus (TGMV), 1 has a bipartite genome that encodes seven open reading frames that are divergently transcribed. The 5Ј-intergenic region separating the transcription units is nearly identical between the two DNA components and includes the plus strand origin of replication (7, 8). The promoter for complementary sense transcription overlaps the replication origin (5, 9) and shares some of the cis-elements involved in origin function (10). A directly repeated sequence, GGTAG, is required for origin recognition (11) and transcriptional repression of the complementary se...

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“…In addition, it has an ATP-/GTPase activity required in the replication process [23], it stimulates expression of proliferating cell nuclear antigen (PCNA) [24] and may interact with a plant homolog of the retinoblastoma protein [25].…”

Section: Introduction 2 Materials and Methodsmentioning

confidence: 99%

Identification of the nicking tyrosine of geminivirus Rep protein

et al. 1995

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Two tyrosines, both located in the amino-terminal domain of the protein, are conserved in geminivirus Rep proteins. The first one is part of the sequence motif-FLTY-whose function is still unknown, and the second one is the central amino acid of a sequence that has been suggested to catalyze replication initiation [33] (see Fig. 1) Here we provide biochemical proof that the tyrosine-103 of the Rep protein tomato yellow leaf curl virus (TYLCV) is the active amino acid of the cleavage/joining reaction.

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A Geminivirus Induces Expression of a Host DNA Synthesis Protein in Terminally Differentiated Plant Cells

Cited by 27 publications

References 0 publications

Stimulation of the cell cycle and maize transformation by disruption of the plant retinoblastoma pathway

Stimulation of the cell cycle and maize transformation by disruption of the plant retinoblastoma pathway

The Multifunctional Character of a Geminivirus Replication Protein Is Reflected by Its Complex Oligomerization Properties

Identification of the nicking tyrosine of geminivirus Rep protein

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