Nucleotide sequence of a gene from chromosome 1D of wheat encoding a HMW-glutenin subunit.

A high molecular weight glutenin gene in hexaploid wheat has been isolated by cloning in bacteriophage lambda and characterized. The gene corresponds to polypeptide 12 encoded by chromosome 1D in the variety "Chinese Spring". The coding sequence predicted contains seven cysteine residues six of which flank a central repetitive region comprising more than 70% of the polypeptide. These findings are related to the role of high molecular weight subunits in the viscoelastic theory of gluten structure.     

Core alpha1,3-fucose is a key part of the epitope recognized by antibodies reacting against plant N-linked oligosaccharides and is present in a wide variety of plant extracts

Carbohydrates have been suggested to account for some IgE cross- reactions between various plant, insect, and mollusk extracts, while some IgG antibodies have been successfully raised against plant glycoproteins. A rat monoclonal antibody raised against elderberry abscission tissue (YZ1/2.23) and rabbit polyclonal antiserum against horseradish peroxidase were screened for reactivity in enzyme-linked immunosorbent assay against a range of plant glycoproteins and extracts as well as neoglycoproteins, bee venom phospholipase, and several animal glycoproteins. Of the oligosaccharides tested, Man3XylFucGlcNAc2(MMXF3) derived from horseradish peroxidase was the most potent inhibitor of the reactivity of both YZ1/2.23 and anti- horseradish peroxidase to native horseradish peroxidase glycoprotein. The reactivity of YZ1/2. 23 and anti-horseradish peroxidase against Sophora japonica lectin was most inhibited by a neoglycoconjugate of bromelain glycopeptide cross-linked to bovine serum albumin, while the defucosylated form of this conjugate was inactive as an inhibitor. A wide range of plant extracts was found to react against YZ1/2.23 and anti-horseradish peroxidase, with particularly high reactivities recorded for grass pollen and nut extracts. All these reactivities were inhibitable with the bromelain glycopeptide/bovine serum albumin conjugate. Bee venom phospholipase and whole bee venom reacted weakly with YZ1/2.23 but more strongly with anti-horseradish peroxidase in a manner inhibitable with the bromelain glycopeptide/bovine serum albumin conjugate, while hemocyanin from Helix pomatia reacted poorly with YZ1/2.23 but did react with anti-horseradish peroxidase. It is concluded that the alpha1, 3-fucose residue linked to the chitobiose core of plant glycoproteins is the most important residue in the epitope recognized by the two antibodies studied, but that the polyclonal anti-horseradish peroxidase antiserum also contains antibody populations that recognize the xylose linked to the core mannose of many plant and gastropod N-linked oligosaccharides.      

Transposon-associated somatic gai-loss sectors in Arabidopsis

The gai mutation of Arabidopsis confers reduced gibberellin responses, and is inherited as a semidominant trait. Somatic sectors displaying wild-type phenotype were observed in plants which were heterozygous for gai and for a linked Ds element, and which also contained a source of the Ac transposase function. The frequency of these sectors was correlated with the level of transposase conferred by the transposase source, suggesting that the sectors are the result of transposon activity. The appearance of the sectors indicates that gai phenotype is restricted to cells containing a functional gai gene copy.     

Step-by-step acquisition of the gibberellin-DELLA growth-regulatory mechanism during land-plant evolution

Angiosperms (flowering plants) evolved relatively recently and are substantially diverged from early land plants (bryophytes, lycophytes, and others [1]). The phytohormone gibberellin (GA) adaptively regulates angiosperm growth via the GA-DELLA signaling mechanism [2-7]. GA binds to GA receptors (GID1s), thus stimulating interactions between GID1s and the growth-repressing DELLAs [8-12]. Subsequent 26S proteasome-mediated destruction of the DELLAs promotes growth [13-17]. Here we outline the evolution of the GA-DELLA mechanism. We show that the interaction between GID1 and DELLA components from Selaginella kraussiana (a lycophyte) is GA stimulated. In contrast, GID1-like (GLP1) and DELLA components from Physcomitrella patens (a bryophyte) do not interact, suggesting that GA-stimulated GID1-DELLA interactions arose in the land-plant lineage after the bryophyte divergence ( approximately 430 million years ago [1]). We further show that a DELLA-deficient P. patens mutant strain lacks the derepressed growth characteristic of DELLA-deficient angiosperms, and that both S. kraussiana and P. patens lack detectable growth responses to GA. These observations indicate that early land-plant DELLAs do not repress growth in situ. However, S. kraussiana and P. patens DELLAs function as growth-repressors when expressed in the angiosperm Arabidopsis thaliana. We conclude that the GA-DELLA growth-regulatory mechanism arose during land-plant evolution and via independent stepwise recruitment of GA-stimulated GID1-DELLA interaction and DELLA growth-repression functions.     

The Fine Structural Observation on the Development of Embryo and Endosperm in the Intergene- rfc Crosses of Fadish ♀ (Raphanus sativus L.) Cabbageo ♂ (Brassica oleracea L.)

The present report deals with the structural abnormalities and abortion of the endosperm, and the related abnormal development of the embryos in the intergeneric crosses of radish (Raphanus sativus L.) ♀ with cabbage (Brassica oleracea L.) ♂. The weak development of ER, the occurence of starch grains in chloroplasts, the curious distribution of chloroplasts around the nuclei, and the earlier formation of cellular endosperm are some primary structure abnormalities of endosperm and they may indicate the poor development, low metabolic activities, and precocious growth in the hybrid endosperm. The endosperm abortion, which starts from chalazal end endosperm, comprises the damage of both structure and function of ER membrane, and the disintegration of nuclei and organelles, or even death. The hybrid embryos degenerated very early in 2-cell stage or even zygote stage in case the endosperm Aborted early. In case of endosperm late-aborted, the hybrid embryos grew for quite a long period of time but become slow down as the endosperm showed abnormal development and started to abort. As the results, the embryos were smaller, the embryo propers and the suspensors showed no growth in step with one another, and the embryo cells appeared structural abnormalities, and finally degenerated and aborted.     

DNA restriction-fragment variation in the gene family encoding high molecular weight (HMW) glutenin subunits of wheat

Restriction enzyme digests of DNA from nullisomic-tetrasomic and intervarietal chromosome substitution lines of wheat were probed with a high molecular weight (HMW) glutenin cDNA. Three restriction endonucleases were used to investigate restriction-fragment differences among five wheat varieties. The results suggest that the hybridizing fragments contain single gene copies and permit the identification of the subunit encoded by each gene. Restriction-fragment variation associated with previously established allelic differences between varieties was observed. Also, there is a clear relationship between the electrophoretic mobility of a HMW subunit and the length of the central repetitive section of the gene encoding it. These results are discussed with reference to the evolution of the HMW glutenin gene family and the uses of restriction-fragment variation in plant breeding and genetics.N.P.H. was supported by a MRC Training Fellowship in Recombinant DNA Technology and a grant from the Perry Foundation. D.B. is supported by EEC Contract GBI-4-027-UK.