Genetically controlled differences in the effects of chlormequat on tetraploid wheat (Triticum turgidum)

Two crosses between Triticum turgidum wheat lines differing in their response to chlormequat (CCC) were tested. In the F₂ population of one cross, which was segregating for the Rht1 dwarfing allele, each plant was cloned by separation of two tillers, one of which was treated with CCC. The tall (rht1/rht1) and the intermediate (Rht1/rht1) genotypes showed a greater response to CCC than the semi-dwarf (Rht1/Rht1) genotype, as expressed by culm length and date of ear emergence. The F₃ families of another cross and their two semi-dwarf parents were grown in a three-replicated field test in paris of rows, one of which was treated with CCC. In one of the parents and in 1/4 of the F₃ families CCC induced a wide-angled tiller growth, suggesting a monogenic control of this growth habit in response to CCC.Based on an M.Sc. thesis presented by the senior author to the Faculty of Agriculture of The Hebrew University of Jerusalem.     

A family of related sequences associated with (TTTAGGG)n repeats are located in the interstitial regions of wheat chromosomes

A family of related sequences associated with (TTTAGGG) _n repeats has been cloned from the wheat cultivar Chinese Spring. These sequences reveal a high level of polymorphism between wheat varieties when used as restriction fragment length polymorphism (RFLP) probes. Although this family of sequences contains motifs homologous to the repeats in the telomeres of wheat, they are located at interstitial sites on wheat chromosomes.     

Detection of ribosomal DNA sites in lentil and chickpea by fluorescent in situ hybridization.

Hybridization sites of an rDNA probe coding for the 18S, 5.8S, and 26S genes were detected on lentil and chickpea somatic chromosomes using fluorescent in situ hybridization. One pair of hybridization sites was detected in cultivated lentil Lens culinaris L. and wild lentil L. orientalis (Boiss.) Hand.-Mazz., and in both the hybridization sites of the ribosomal probe correspond to the secondary constriction. In cultivated chickpea Cicer arietinum three pairs of rDNA sites were detected and in the wild C. reticulatum two pairs were detected. The karyotypic relationship between the cultivated C. arietinum and its wild progenitor C. reticulatum is discussed.     

A family of related sequences associated with (TTTAGGG)n repeats are located in the interstitial regions of wheat chromosomes

A family of related sequences associated with (TTTAGGG) _n repeats has been cloned from the wheat cultivar Chinese Spring. These sequences reveal a high level of polymorphism between wheat varieties when used as restriction fragment length polymorphism (RFLP) probes. Although this family of sequences contains motifs homologous to the repeats in the telomeres of wheat, they are located at interstitial sites on wheat chromosomes.     

Peptide-membrane interactions studied by a new phospholipid/polydiacetylene colorimetric vesicle assay

Interactions between peptides and lipid membranes play major roles in numerous physiological processes, such as signaling, cytolysis, formation of ion channels, and cellular recognition. We describe a new colorimetric technique for studying peptide-membrane interactions. The new assay is based on supramolecular assemblies composed of phospholipids embedded in a matrix of polydiacetylene (PDA) molecules. The phospholipid/PDA vesicle solutions undergo visible color changes upon binding of membrane peptides. Experiments utilizing various analytical techniques confirm that the blue-to-red color transitions of the phospholipid/PDA vesicles are directly related to adoption of helical conformations by the peptides and their association with the lipids. Spectroscopic data indicate that the colorimetric transitions are correlated with important molecular parameters, such as the degree of penetration of the peptides into lipid bilayers, and the mechanisms of peptide-lipid binding. The results suggest that the new colorimetric assay could be utilized for studying interactions and organization of membrane peptides.     

Uncovering cryptic species diversity of a termite community in a West African savanna

To uncover the termite species diversity of a natural African savanna ecosystem, we combined morphological analyses and sequencing of three gene fragments (cytochrome oxidase I, cytochrome oxidase II and 28SrDNA, total length about 2450 bp) to infer putative species from phylogenetic trees. We identified 18 putative species clusters with high support values and which we retrieved consistently. Samples from two genera (Ancistrotermes and Microcerotermes) were excluded from the mitochondrial phylogenetic analyses as they might represent nuclear mitochondrial sequences (NUMTs). In total, our data suggest a species richness of at least 20 species, all but one belonging to the Termitidae (higher termites), and among them the fungus-growing Macrotermitinae were most prevalent with at least nine putative species. Within the fungus-growers the most species-rich genus was Microtermes and its four putative species were all cryptic species. Their abundance in the samples suggests that they play an important ecological role which is completely unstudied also due to the lack of reliable identification means. Our study shows that morphological traits are unreliable means of species identification for several termite taxa. Yet reliable and consistent identification is necessary for studying the functional role of termites in ecosystem and global processes.     

Allelic diversity associated with aridity gradient in wild emmer wheat populations

The association between allelic diversity and ecogeographical variables was studied in natural populations of wild emmer wheat [ Triticum turgidum ssp. dicoccoides (Körn.) Thell.], the tetraploid progenitor of cultivated wheat. Patterns of allelic diversity in 54 microsatellite loci were analyzed in a collection of 145 wild emmer wheat accessions representing 25 populations that were sampled across naturally occurring aridity gradient in Israel and surrounding regions. The obtained results revealed that 56% of the genetic variation resided among accessions within populations, while only 44% of the variation resided between populations. An unweighted pair-group method analysis (UPGMA) tree constructed based on the microsatellite allelic diversity divided the 25 populations into six major groups. Several groups were comprised of populations that were collected in ecologically similar but geographically remote habitats. Furthermore, genetic differentiation between populations was independent of the geographical distances. An interesting evolutionary phenomenon is highlighted by the unimodal relationship between allelic diversity and annual rainfall ( r  = 0.74, P  < 0.0002), indicating higher allelic diversity in populations originated from habitats with intermediate environmental stress (i.e. rainfall 350–550 mm year⁻¹). These results show for the first time that the 'intermediate-disturbance hypothesis', explaining biological diversity at the ecosystem level, also dominates the genetic diversity within a single species, the lowest hierarchical element of the biological diversity.     

Isolation and characterization of chromosome-specific DNA sequences from a chromosome arm genomic library of common wheat

Isolation, physical mapping and polymorphism of chromosome-specific DNA sequences in wheat are reported. Following the microdissection of the long arm of chromosome 5B (5BL) of common wheat, its DNA was amplified by degenerate oligonucleotide-primed PCR and directly cloned into plasmid vectors. Characterization of the chromosome arm library showed that ∼55% of the inserts are of low-copy nature. Southern analysis using aneuploid lines of common wheat revealed that five of 11 low-copy inserts analyzed map to chromosome arm 5BL; four of these are 5BL-specific. By deletion mapping, the 5BL-specific sequences were located to sub- chromosome arm regions. Based on the hybridization patterns of three 5BL-specific sequences to DNA from a diverse collection of goat-grass ( Aegilops ) and wheat ( Triticum ) species, it was concluded that these sequences emerged at different times in the course of evolution of this group of plant species.