Occurrence of levels of cis‐ and trans‐zeatin ribosides in the culture medium of a virulent strain of Agrobacterium tumefaciens

McCloskey, James A.; Hashizume, Takeshi; Basile, Brenda; Ohno, Yosuke; Sonoki, Shigenori

doi:10.1016/0014-5793(80)80788-5

Cited by 23 publications

(9 citation statements)

References 12 publications

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“…wt. Agrobacteria do produce plant hormones like cytokinins and auxin, and Ti-plasmids influence their metabolism (Claeys et al, 1978;Liu and Kado, 1979;McCloskey et al, 1980;Weiler and Spanier, 1981;Liu et al, 1982;Regier and Morris, 1982). wt.…”

Section: Discussionmentioning

confidence: 99%

The conserved part of the T-region in Ti-plasmids expresses four proteins in bacteria.

et al. 1983

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The T‐region of Ti‐plasmids expresses four proteins (mol. wts. 74,000, 49,000, 28,000 and 27,000) in Escherichia coli minicells. Promoter activities are determined by sequences within the T‐region, and the protein‐coding regions map in that part of the T‐region which is highly conserved in octopine and nopaline plasmids and which is responsible for shoot and root inhibition when expressed in plant cells. Three of the regions expressed in bacteria correlate with three regions which are transcribed in transformed plant cells; the fourth protein‐coding region has no corresponding transcript in plants. At least three of the proteins synthesized in E. coli minicells are also expressed in cell‐free systems prepared from E. coli and from Agrobacterium tumefaciens; the fourth protein (mol. wt. 49,000) is poorly expressed in both cell‐free extracts. The possibility is discussed that the same genes are expressed in Agrobacteria and in transformed plant cells and that in both cases the gene products mediate growth regulatory effects to non‐transformed plant cells.

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Section: Discussionmentioning

confidence: 99%

The conserved part of the T-region in Ti-plasmids expresses four proteins in bacteria.

et al. 1983

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“…Phytohormone production has been observed in both Ti plasmid-transformed plant cells and the inciting bacteria (40)(41)(42)(43)15). It is possible that the same genes are responsible for this synthesis in the plant tissue and in A. tumefaciens, but further work will be necessary to establish this point.…”

Section: Discussionmentioning

confidence: 99%

Identification of a cloned cytokinin biosynthetic gene

Barry

Rogers

Fraley

et al. 1984

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

366

156

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A small region of the Ti plasmid (the tmr locus), thought to be involved in phytohormone metabolism in Agrobacterium tumefaciens-transformed plant tissue, was cloned and expressed in Escherichia coli. By enzyme assay, the tmr locus was shown to encode isopentenyltransferase, an enzyme that catalyzes the first step in cytokinin biosynthesis.Crown gall disease, characterized by the development of neoplastic growth on the infected plant, affects many dicotyledonous plants and is caused by the soil bacterium Agrobacterium tumefaciens (1). The induction and maintenance of the tumor is dependent upon the integration into the plant genome and expression of a DNA fragment (T-DNA) from the large virulence plasmid (Ti) harbored by the bacterium (2-7). In tissue culture the Agrobacterium-induced tumors have been shown to be autotrophic for phytohormones (8), specifically for auxins and cytokinins. That the transforming T-DNA was involved in the alteration in the endogenous hormone synthesis was suggested by the identification of A. tumefaciens isolates that induced tumors with abnormal morphologies, characteristic of hormonal imbalance, such as the overproduction of shoots or roots (9-13). The loci responsible for such altered morphologies have been mapped to the T-DNA and have been shown to correlate with alterations in the phytohormone levels in the tumors (14, 15). Specifically, mutants in the tms ("shooty") and tml ("large") loci result in over production of cytokinins, while those in the tmr ("rooty") locus result in a very large decrease in endogenous cytokinin levels.The enzyme central to all cytokinin biosynthesis is A2-isopentenyl pyrophosphate:5'-AMP A2-isopentenyltransferase (EC 2.5.1.-) commonly referred to as isopentenyl transferase (16). The product of this reaction is isopentenyladenosine monophosphate (iPeAMP) (Fig. 1), which by dephosphorylation is converted to the cytokinin isopentenyladenosine (iPeA) and which is the precursor to all other cytokinins (17). The tms and tml defects result in a large increase in isopentenyltransferase activity in the tumors, while the tmr defects result in a decrease in activity to a level lower than that found even in normal tissue (14). While the tms, tml, and tmr results are consistent with the regulatory role of these loci on the expression or activity of endogenous cytokinin biosynthesis, the results are also consistent with the tmr locus directly encoding a biosynthetic enzyme.Transcriptional and translation maps of the T-DNA regions have been determined recently for both the octopine and nopaline Ti plasmids, and the tmr gene transcript has been identified in tumors induced by both plasmid types (11,(18)(19)(20)(21)(22). The tmr region from the nopaline plasmid pTi T37 was cloned and the nucleotide sequence was determined (23). An open reading frame encoding a protein of 27 kilodaltons (kDa) was identified in this sequence, as has also been found for the same region of the octopine Ti plasmid (24). A protein of this size has been shown to be expressed from ...

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“…The two sets of data for Z. mays kernels (Table III) (16,22), but anti-[9RJZ serum has very low cross-reactivity to these isomers (21,37) and is therefore not useful for detecting them in samples. A. tumefaciens has been found to produce Z (10,16), but this cytokinin was not detected in the volume of sample assayed in the present study.…”

Section: -~Ajmentioning

confidence: 99%

Quantitation of Cytokinins in Biological Samples Using Antibodies Against Zeatin Riboside

Badenoch‐Jones¹,

Letham²,

Parker³

et al. 1984

Plant Physiol.

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The cross-reactivity of antibodies elicited in rabbits against zeatin riboside, to a wide range of naturally occurring cytokinins, was examined. As well as to zeatin riboside, the antisera cross-reacted to a considerable extent with zeatin, lupinic acid, zeatin-9-glucoside, zeatin riboside 5'-monophosphate and to a much lesser, but measurable extent, with dihydrozeatin riboside and dihydrozeatin. Chromatographic methods were devised which allowed separation of all these cross-reactive com- particularly sensitive method. However, when antisera are elicited against one of a class of phytohormones, such as cytokinins, several members of the class may cross-react, each to differing extents. An advantage of multiple cross-reactivity is the potential ability to quantitate each cross-reactive compound, but a disadvantage is that data obtained by RIA on crude extracts containing a mixture of these cross-reactive hormones, are somewhat meaningless. Furthermore, although RIA is often regarded as a highly specific method (38), the technique is vulnerable to nonspecific interference from substances in the sample which either react with the antiserum or alter its reaction with the compound(s) being assayed (see 6).The aim of the current investigation was therefore to assess the reliability of RIA for quantitating cytokinins in a variety of extracts and to develop systems that enabled the separation of all cytokinins known to cross-react with the anti-[9R]Z-serum. MATERIALS AND METHODSPlant Material. Lupin plants (Lupinus luteus L. cv Weiko III) were grown from seed (source: Westralian Farmers Co-op., Perth, Australia) in a greenhouse with natural light at 15 to 25°C. Sweet corn plants (Zea mays, Fl hybrid lochief) were grown from seed (source: Yeates Seeds) in field plots (spring, summer). Immature lupin seeds and sweet corn kernels, which were soft and contained little storage material, were removed from the pods and cobs, respectively, frozen in liquid nitrogen, and,stored at -1 98°C until required. Crown gall tumor tissue of Datura innoxia Mill line B6 was a gift from Dr. L. M. S. Palni. The callus was grown at 25°C in 250-ml conical flasks containing 100 ml hormone-free B5 medium (14)

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Occurrence of levels of cis‐ and trans‐zeatin ribosides in the culture medium of a virulent strain of Agrobacterium tumefaciens

Cited by 23 publications

References 12 publications

The conserved part of the T-region in Ti-plasmids expresses four proteins in bacteria.

The conserved part of the T-region in Ti-plasmids expresses four proteins in bacteria.

Identification of a cloned cytokinin biosynthetic gene

Quantitation of Cytokinins in Biological Samples Using Antibodies Against Zeatin Riboside

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