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Lotus corniculatus nodulation specificity is changed by the presence of a soybean lectin gene 总被引:5,自引:0,他引:5
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Plant lectins have been implicated as playing an important role in mediating recognition and specificity in the Rhizobium-legume nitrogen-fixing symbiosis. To test this hypothesis, we introduced the soybean lectin gene Le1 either behind its own promoter or behind the cauliflower mosaic virus 35S promoter into Lotus corniculatus, which is nodulated by R. loti. We found that nodulelike outgrowths developed on transgenic L. corniculatus plant roots in response to Bradyrhizobium japonicum, which nodulates soybean and not Lotus spp. Soybean lectin was properly targeted to L. corniculatus root hairs, and although infection threads formed, they aborted in epidermal or hypodermal cells. Mutation of the lectin sugar binding site abolished infection thread formation and nodulation. Incubation of bradyrhizobia in the nodulation (nod) gene-inducing flavonoid genistein increased the number of nodulelike outgrowths on transgenic L. corniculatus roots. Studies of bacterial mutants, however, suggest that a component of the exopolysaccharide surface of B. japonicum, rather than Nod factor, is required for extension of host range to the transgenic L. corniculatus plants. 相似文献
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The large N-linked oligosaccharides released from Schizosaccharomyces pombe
by endo-beta-N-acetylglucosaminidase H were examined to determine how the
negatively chargedpyruvylated galactoses present (Gemmill,T.R., and
Trimble,R.B., 1996, J. Biol. Chem ., 271, 25945-25949) were attached to the
oligosaccharide chains. Binding of biotinylated human serum amyloid P and
peanut agglutinin to native and depyruvylated S.pombe glycoproteins,
respectively, indicated that the pyruvylated epitope was likely to be in
the beta configuration. Examination by high- field 1H NMR of whole glycans
and a disaccharide fragment released from them on partial acid hydrolysis
showed that the pyruvylated galactose species was in fact beta1,3-linked to
a second galactose, and this occurred an average of five to six times on
nominal Gal57Man64GlcNAc N- glycans. The pyruvate-2,(4,6)Gal-beta1,3Gal
epitope is chemically similar to acetaldehyde-Galbeta1,3Gal groups found on
the glycoproteins from Paramyxovirus-infected bovine kidney cells (Prehm,
P., Scheid,A. and Choppin,P.W. ,1979, J. Biol. Chem ., 254, 9669-9677). The
1:1 stoichiometry between pyruvate and beta-linked galactose in these
S.pombe glycans indicates that either pyruvate addition to terminal
beta1,3Gal is highly efficient or that pyruvylated Gal is transferred en
bloc to alpha1,2-linked Gal residues in theN-linked chains. In
contradiction to many galactomannan-producing fungi, which add substantial
amounts of Gal in the furanose form to their glycoproteins, all detectable
Gal in the large S.pombe galactomannans is in the pyranose form, as found
in higher eukaryotes. The current work shows that the S.pombe outer chain
structure is a poly-alpha1,6Man backbone 2- O-substituted with either Gal
or the pyruvylated galactobiose and contains little alpha1,2-linked or
2-O-substituted Man. This is in contrast to the S. cerevisiae outer chain,
which is poly-alpha1,6Man substituted with alpha1,2-linked Man sidechains
(Ballou,C.E. ,1990, Methods Enzymol , 185, 440-470).
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Structural perturbations in DNA caused by bis-intercalation of ditercalinium visualised by atomic force microscopy
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Berge T Jenkins NS Hopkirk RB Waring MJ Edwardson JM Henderson RM 《Nucleic acids research》2002,30(13):2980-2986
Atomic force microscopy (AFM) has been used to examine perturbations in the tertiary structure of DNA induced by the binding of ditercalinium, a DNA bis-intercalator with strong anti-tumour properties. We report AFM images of plasmid DNA of both circular and linearised forms showing a difference in the formation of supercoils and plectonemic coils caused at least in part by alterations in the superhelical stress upon bis-intercalation. A further investigation of the effects of drug binding performed with 292 bp mixed-sequence DNA fragments, and using increment in contour length as a reliable measure of intercalation, revealed saturation occurring at a point where sufficient drug was present to interact with every other available binding site. Moment analysis based on the distribution of angles between segments along single DNA molecules showed that at this level of bis-intercalation, the apparent persistence length of the molecules was 91.7 ± 5.7 nm, approximately twice as long as that of naked DNA. We conclude that images of single molecules generated using AFM provide a valuable supplement to solution-based techniques for evaluation of physical properties of biological macromolecules. 相似文献
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MOTIVATION: Recently, we described a Maximum Weighted Matching (MWM) method
for RNA structure prediction. The MWM method is capable of detecting
pseudoknots and other tertiary base-pairing interactions in a
computationally efficient manner (Cary and Stormo, Proceedings of the Third
International Conference on Intelligent Systems for Molecular Biology, pp.
75-80, 1995). Here we report on the results of our efforts to improve the
MWM method's predictive accuracy, and show how the method can be extended
to detect base interactions formerly inaccessible to automated RNA modeling
techniques. RESULTS: Improved performance in MWM structure prediction was
achieved in two ways. First, new ways of calculating base pair likelihoods
have been developed. These allow experimental data and combined statistical
and thermodynamic information to be used by the program. Second, accuracy
was improved by developing techniques for filtering out spurious base pairs
predicted by the MWM program. We also demonstrate here a means by which the
MWM folding method may be used to detect the presence of base triples in
RNAs. AVAILABILITY: http://www.cshl.org/mzhanglab/tabaska/j axpage. html
CONTACT: tabaska@cshl.org
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