Common wheat, Triticum aestivum, is an allohexaploid species consisting of three different genomes (A, B, and D). The three genomes were simultaneously discriminated with different colors. Biotinylated total genomic DNA of the diploid A genome progenitor Triticum urartu, digoxigenin-labeled total genomic DNA of the diploid D genome progenitor Aegilops squarrosa, and nonlabeled total genomic DNA of one of the possible B genome progenitors Ae. speltoides were hybridized in situ to metaphase chromosome spreads of Triticum aestivum cv. Chinese Spring. For detection, only two fluorochromes, fluorescein and rhodamine, were used. The A, B, and D genomes were simultaneously detected by their yellow, brown, and orange fluorescence, respectively. The genomic fluorescence in situ hybridization pattern of chromosome 4A of cv. Chinese Spring wheat showed that the distal 32% of the long arm was derived from a B genome chromosome. Furthermore, by using two highly repeated sequence probes, pSc 119.2 and pAsl, and two fluorochromes simultaneously, we were able to identify all B and D genome chromosomes and chromosomes 1A, 4A, and 5A of wheat.

Novel lipid microstructures with various morphologies have been synthesized using a series of amino acid terminated diacetylenic lipids, and the chromatic transitions of the polymerized microstructures have been characterized by UV−vis and FTIR spectroscopies. The observed morphologies for the microstructures include tubule, helix, ribbon, sheet, braided fiber, and planar platelet, formation of which has shown strong dependency on the chemical structure of the headgroup. All amino acid lipids studied in this work form microstructures that allow polymerization by UV irradiation to yield a blue appearance. Molecular chirality, electrostatic interactions, and hydrogen-bonding interactions in the headgroup region determine the formation of microstructures with twisted features, while nonchiral molecules do not form curved structures. The polymerized lipid microstructures exhibit similar colorimetric properties as observed for related bilayer vesicles, undergoing a blue-to-red color transition in response to thermal and pH changes. Microstructures with hydrophobic headgroup lipids are more sensitive to pH change than those with hydrophilic headgroups. For hydrophilic headgroup lipids, microstructures are more pH-resistant relative to their vesicle counterparts. FTIR studies suggest that thermal and pH-induced chromism of PDA microstructures proceed by different pathways. A mechanism is proposed that links function and change of hydrogen-bonding interactions to the observed chromatic behaviors of the PDA microstructures. In thermochromism, hydrogen-bonding interactions lock in the lipid headgroups so that the temperature-induced gauche−trans conformational transition of the side chains imposes strain on the assembly. In pH-induced chromism, surface ionization and breakdown of hydrogen-bonding interactions lead to reorganization of the headgroups that affects the electron delocalization along the conjugated backbone.

Genes and cDNAs for starch-branching enzyme II (SBEII) have been isolated from libraries constructed from Aegilops tauschii and wheat (Triticum aestivum) endosperm, respectively. One class of genes has been termed wSBEII-DA1 and encodes the N terminus reported for an SBEII from wheat endosperm. On the basis of phylogenetic comparisons with other branching enzyme sequences, wSBEII-DA1 is considered to be a member of the SBEIIa class. The wSBEII-DA1 gene consists of 22 exons with exons 4 to 21 being identical in length to the maize (Zea mays) SBEIIb gene, and the gene is located in the proximal region of the long arm of chromosome 2 at a locus designated sbe2a. RNA encoding SBEIIa can be detected in the endosperm from 6 d after flowering and is at its maximum level from 15 to 18 d after anthesis. Use of antibodies specific for SBEIIa demonstrated that this protein was present in both the soluble and granule bound fractions in developing wheat endosperm. We also report a cDNA sequence for SBEIIa that could arise by variant transcription/splicing. A second gene, termed wSBEII-DB1, was isolated and encodes an SBEII, which shows greater sequence identity with SBEIIb-type sequences than with SBEIIa-type sequences. Comparisons of SBEII gene structures among wheat, maize, and Arabidopsis indicate the lineage of the SBEII genes.

Studies of maize starch branching enzyme mutants suggest that the amylose extender high amylose starch phenotype is a consequence of the lack of expression of the predominant starch branching enzyme II isoform expressed in the endosperm, SBEIIb. However, in wheat, the ratio of SBEIIb and SBEIIa expression are inversely related to the expression levels observed in maize and rice. Analysis of RNA at 15 days post anthesis suggests that there are about 4-fold more RNA for SBE IIa than for SBE IIb. The genes for SBE IIa and SBE IIb from wheat are distinguished in the size of the first three exons, allowing isoform-specific antibodies to be produced. These antibodies were used to demonstrate that in the soluble fraction, the amount of SBE IIa protein is two to three fold higher than SBIIb, whereas in the starch granule, there is two to three fold more SBE IIb protein amount than SBE IIa. In a further difference to maize and rice, the genes for SBE IIa and SBE IIb are both located on the long arm of chromosome 2 in wheat, in a position not expected from rice-maize-wheat synteny.