The Agrobacterium tumefaciens T-DNA gene 6b is an onc gene

Hooykaas, Paul J. J.; Dulk-Ras, H. den; Schilperoort, R. A.

doi:10.1007/bf00019519

Cited by 73 publications

(45 citation statements)

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“…Various phenotypic effects associated with the expression of 6b have been reported, as follows: (1) formation of tumors on certain plants (Hooykaas et al, 1988;Spanier et al, 1989;Tinland et al, 1989Tinland et al, , 1992; (2) stimulation of the ipt -induced and iaaM / iaaH -induced division of cells (Tinland et al, 1989(Tinland et al, , 1990Wabiko and Minemura, 1996); (3) reduction in the formation of shoots on leaf discs that is normally induced by appropriate levels of exogenous or endogenous cytokinin (Spanier et al, 1989); (4) generation of shoot-bearing calli on leaf discs on phytohormone-free medium (Wabiko and Minemura, 1996); (5) inhibition of the growth of Rol -induced hairy roots via the induction of an undifferentiated state and the formation of calli (Tinland et al, 1990); and (6) alterations in the morphology of leaves of transgenic tobacco plants that express the 6b gene (Tinland et al, 1992;Wabiko and Minemura, 1996). Although there are some discrepancies among previously reported results (Leemans et al, 1982;Ream et al, 1983), it is accepted generally that the product of 6b stimulates the proliferation of plant cells and affects the development of 1 Current address: National Institute for Basic Biology, 38 Nishigounaka, Myo-daiji-cho, Okazaki 444-8585, Japan.…”

Section: Introductionmentioning

confidence: 99%

“…It has been suggested that the 6b gene might function in the activation and/or inactivation of cytokinin and auxin (Hooykaas et al, 1988;Spanier et al, 1989); it might increase and/or decrease the sensitivity of transformed cells to these plant hormones (Hooykaas et al, 1988;Tinland et al, 1989) by modifying putative hormone transport systems or reporters (Spanier et al, 1989); its product might interact with ipt and iaa genes and/or their products (Tinland et al, 1989) and/or it might stimulate signal perception systems (Wabiko and Minemura, 1996). It also has been proposed that the 6b gene might affect the concentration of endogenous plant hormones in transformed cells (Spanier et al, 1989).…”

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The Protein Encoded by Oncogene 6b from Agrobacterium tumefaciens Interacts with a Nuclear Protein of Tobacco

et al. 2002

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The 6b gene in the T-DNA from Agrobacterium has oncogenic activity in plant cells, inducing tumor formation, the phytohormone-independent division of cells, and alterations in leaf morphology. The product of the 6b gene appears to promote some aspects of the proliferation of plant cells, but the molecular mechanism of its action remains unknown. We report here that the 6b protein associates with a nuclear protein in tobacco that we have designated NtSIP1 (for Nicotiana tabacum 6b-interacting protein 1). NtSIP1 appears to be a transcription factor because its predicted amino acid sequence includes two regions that resemble a nuclear localization signal and a putative DNA binding motif, which is similar in terms of amino acid sequence to the triple helix motif of rice transcription factor GT-2. Expression in tobacco cells of a fusion protein composed of the DNA binding domain of the yeast GAL4 protein and the 6b protein activated the transcription of a reporter gene that was under the control of a chimeric promoter that included the GAL4 upstream activating sequence and the 35S minimal promoter of Cauliflower mosaic virus . Furthermore, nuclear localization of green fluorescent protein-fused 6b protein was enhanced by NtSIP1. A cluster of acidic residues in the 6b protein appeared to be essential for nuclear localization and for transactivation as well as for the hormone-independent growth of tobacco cells. Thus, it seems possible that the 6b protein might function in the proliferation of plant cells, at least in part, through an association with NtSIP1. INTRODUCTIONAgrobacterium cells that harbor a Ti plasmid induce the formation of crown gall tumors on dicotyledonous plants. Upon infection of a plant by Agrobacterium, a specific region of the Ti plasmid, known as T-DNA, is transferred to the plant cell and integrated into the chromosomal DNA in the nucleus. Plant cells that have been transformed with T-DNA can proliferate autonomously to generate a tumor, which is a consequence, for the most part, of the expression of genes that are responsible for the biosynthesis of auxin; and cytokinin ( iaaM [ tms1 ] or iaaH [ tms2 ] for auxin; ipt [ tmr ] for cytokinin) in the T-DNA (Weiler and Spanier, 1981; Akiyoshi et al., 1984).In addition to these genes, gene 6b , which is localized at the tml locus (Garfinkel et al., 1981) and has been found in the T-DNA of all strains of Agrobacterium (Willmitzer et al., 1983;Otten and De Ruffray, 1994), also is expressed in tumor cells (Willmitzer et al., 1983) and appears to play a role in the proliferation of plant cells. Various phenotypic effects associated with the expression of 6b have been reported, as follows: (1) formation of tumors on certain plants (Hooykaas et al., 1988;Spanier et al., 1989;Tinland et al., 1989Tinland et al., , 1992; (2) stimulation of the ipt -induced and iaaM / iaaH -induced division of cells (Tinland et al., 1989(Tinland et al., , 1990Wabiko and Minemura, 1996); (3) reduction in the formation of shoots on leaf discs that is normally induced by appr...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

The Protein Encoded by Oncogene 6b from Agrobacterium tumefaciens Interacts with a Nuclear Protein of Tobacco

et al. 2002

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“…Infection with either gene leads to the formation of undifferentiated tumors on a limited number of host plants (Hooykaas et al, 1988;Otten and Schmidt, 1998). Similarly, overexpression of the KNAT2 and CycD3 genes causes an auxin-and/or cytokininindependent tumor formation on Arabidopsis leaves (Dockx et al, 1996;Riou-Khamlichi et al, 1999).…”

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Hormone Autotrophic Growth and Differentiation Identifies Mutant Lines of Arabidopsis with Altered Cytokinin and Auxin Content or Signaling

et al. 2000

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We describe mutant tissue lines of Arabidopsis that are able to grow in vitro as callus on hormone-free medium. The 14 lines presented here show different hormone autotrophic differentiation behaviors that can be classified into three categories: (a) forming roots (rooty callus), (b) forming shoots or shoot-like structures (shooty callus), or (c) growing without organ formation (callus). Three fast-growing lines showed altered steady-state mRNA levels of the Cdc2 and CycD3 cell cycle genes. Three of the six rooty callus lines contained about 20-to 30-fold higher levels of auxins than wild-type callus. These and two other lines with normal auxin content showed an increased steady-state level of IAA1 and IAA2 transcripts in the absence of exogenous auxin. Five of the six shooty callus lines had increased steady-state mRNA levels of the CKI1 gene and/or of the homeobox genes KNAT1 and STM, suggesting that the phenotype is linked to altered cytokinin signaling. Also, one cytokinin-overproducing line with only 5% of wild-type cytokinin oxidase activity was identified. These results indicate that screening for hormone-autonomous growth identifies mutants with altered hormone content or signaling.

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“…However, conservation of 6b in the T-DNA regions of many Ti plasmids (Otten and De Ruffray, 1994) suggests a role for the gene in the neoplastic diseases caused by transformation with T-DNA. It has been proposed that the 6b gene might play a more critical role in tumorigenicity in certain specific species of the host plant (Hooykaas et al, 1988). If the efficiency of the formation of crown gall tumors depends on levels of expression of plant cell divisionrelated genes that might be supported by combinatorial functions of the products of the hormone-synthesizing genes from the T-DNA mentioned above and of 6b, which encodes a histone chaperone-like protein, 6b might play a more critical role in the formation of crown galls in host plants that are relatively insensitive to the actions of the phytohormones.…”

Section: Possible Roles Of 6b In the Formation Of Crown Gall Tumorsmentioning

confidence: 99%

“…Various hypotheses have been proposed to explain the effects of 6b on the growth of plant cells (Leemans et al, 1982;Ream et al, 1983;Hooykaas et al, 1988;Tinland et al, 1992;Wabiko and Minemura, 1996). This gene modulates the inductive effects of cytokinins on shoot development (Spanier et al, 1989); it interferes with the induction and elongation of roots in an auxindependent rolABC-based rooting assay, suggesting that 6b might reduce the effect of high levels of auxin to maintain cells in an undifferentiated state (Tinland et al, 1990); and it enhances the effects of both auxin and cytokinin on crown gall formation (Canaday et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

An Oncoprotein from the Plant PathogenAgrobacteriumHas Histone Chaperone–Like Activity

et al. 2007

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Protein 6b, encoded by T-DNA from the pathogen Agrobacterium tumefaciens, stimulates the plant hormone–independent division of cells in culture in vitro and induces aberrant cell growth and the ectopic expression of various genes, including genes related to cell division and meristem-related class 1 KNOX homeobox genes, in 6b-expressing transgenic Arabidopsis thaliana and Nicotiana tabacum plants. Protein 6b is found in nuclei and binds to several plant nuclear proteins. Here, we report that 6b binds specifically to histone H3 in vitro but not to other core histones. Analysis by bimolecular fluorescence complementation revealed an interaction in vivo between 6b and histone H3. We recovered 6b from a chromatin fraction from 6b-expressing plant cells. A supercoiling assay and digestion with micrococcal nuclease indicated that 6b acts as a histone chaperone with the ability to mediate formation of nucleosomes in vitro. Mutant 6b, lacking the C-terminal region that is required for cell division–stimulating activity and interaction with histone H3, was deficient in histone chaperone activity. Our results suggest a relationship between alterations in nucleosome structure and the expression of growth-regulating genes on the one hand and the induction of aberrant cell proliferation on the other.

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The Agrobacterium tumefaciens T-DNA gene 6b is an onc gene

Cited by 73 publications

References 14 publications

The Protein Encoded by Oncogene 6b from Agrobacterium tumefaciens Interacts with a Nuclear Protein of Tobacco

The Protein Encoded by Oncogene 6b from Agrobacterium tumefaciens Interacts with a Nuclear Protein of Tobacco

Hormone Autotrophic Growth and Differentiation Identifies Mutant Lines of Arabidopsis with Altered Cytokinin and Auxin Content or Signaling

An Oncoprotein from the Plant PathogenAgrobacteriumHas Histone Chaperone–Like Activity

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