Ds Element Research Articles

Technological aspects of the development of thermal vacuum installation for drying grain with simultaneous dehydration and disinsection

The Ukraine is one of the largest producers of grain products. Its natural and climatic conditions are such that annually from 50 to 80 % of the harvested crop of grain crops is subject to drying and disinfection. Drying and simultaneous disinsection of grain are the main technological operations for removing harmful moisture from grain material and freeing it from barn pests, which on a national scale makes it possible to avoid millions of losses. The article provides materials on the development of a highly efficient environmentally friendly installation and energy-saving technology of dehydration with simultaneous disinfection of wet grain, which makes it possible to dry grain in a short period of time to a moisture content of 12...14 % and destroy pests. A brief review discusses the main drying units, which are of the convective type and mainly use heated air. Their main positive and negative aspects of use are analyzed. An experimental model of the developed highly efficient environmentally friendly grain drying plant with physical and mathematical justification is presented. Thus, at the same time, such indicators as the speed of grain swirling (υВ) at different temperatures, the value of the centrifugal force of the grain (F) moving in the cavity of the heating element through a spiral channel were calculated. The instantaneous process of thermal energy transfer from the heater wall to the wet grain is substantiated.Thus, the surface element (dS) of a wet grain receives a flow of thermal energy (dQ) with a temperature (Т) in a short period of time (∆τ) with a heat transfer coefficient (a). It has been experimentally proven that grain dehydration is affected by at least three parameters: the heating temperature, its humidity, and the pressure in the vacuum chamber. All parameters are interconnected and affect technological indicators. Thus, the use of thermovacuum technology is an alternative to traditional high-temperature methods of drying grain crops. Key words: thermovacuum dehydration of grain, drying, disinsection.

A rice seed-specific glycine-rich protein OsDOR1 interacts with GID1 to repress GA signaling and regulates seed dormancy

Seed dormancy is an important agronomic trait under the control of complex genetic and environmental interactions, which have not been yet comprehensively understood. From the field screening of rice mutant library generated by a Ds transposable element, we identified a pre-harvest sprouting (PHS) mutant dor1. This mutant has a single insertion of Ds element at the second exon of OsDOR1 (LOC_Os03g20770), which encodes a novel seed-specific glycine-rich protein. This gene successfully complemented the PHS phenotype of dor1 mutant and its ectopic expression enhanced seed dormancy. Here, we demonstrated that OsDOR1 protein binds to the GA receptor protein, OsGID1 in rice protoplasts, and interrupts with the formation OsGID1-OsSLR1 complex in yeast cells. Co-expression of OsDOR1 with OsGID1 in rice protoplasts attenuated the GA-dependent degradation of OsSLR1, the key repressor of GA signaling. We showed the endogenous OsSLR1 protein level in the dor1 mutant seeds is significantly lower than that of wild type. The dor1 mutant featured a hypersensitive GA-response of α-amylase gene expression during seed germination. Based on these findings, we suggest that OsDOR1 is a novel negative player of GA signaling operated in the maintenance of seed dormancy. Our findings provide a novel source of PHS resistance.

Toward the development of Ac/Ds transposon-mediated gene tagging system for functional genomics in oat (Avena sativa L.).

Cultivated oat (Avena sativa L.) is an important cereal grown worldwide due to its multifunctional uses for animal feed and human food. Oat has lagged behind other cereals in the genetic and genomic studies attributed to its large and complex genomes. Transposon-based genome characterization has been utilized successfully for identifying and determining gene function in large genome cereals. To develop gene tagging and gene-editing resources for oat, maize Activator (Ac) and Dissociation (Ds) transposons were introduced into the oat genome using the biolistic delivery system. A total of 2035 oat calli were bombarded and twenty-four independent, stable transgenic events were obtained. Transformation frequencies were up to 19.0%, and 1.9% for bialaphos and hygromycin selection, respectively. Re-mobilization of the non-autonomous Ds element, by introducing Ac transposase source, led to a transposition frequency up to 16.8%. The properties of ten unique flanking sequences have been characterized to reveal the Ds-tagged sites in the oat genome. Genes at Ds insertion sites showed homology to gibberellin 20-oxidase 3, (1,3;1,4)-beta-D-glucan synthase, and aspartate kinase. This Ac/Ds transposon-based gene tagging system could facilitate and expedite functional genomic studies in oat.

Activation of CDC48 and acetyltransferase encoding genes contributes to enhanced abiotic stress tolerance and improved productivity traits in rice

World-wide crop productivity is highly impacted by various extreme environmental conditions. In the present investigation, activation tagged (AT) line A10-Ds-RFP6 of rice endowed with improved agronomic attributes was tested for its tolerance ability against drought and salinity stress conditions as well as identification of genes associated with these traits. Under both drought and salinity stress conditions, A10-Ds-RFP6 line exhibited increased seed germination rates and improved plant growth characteristics at seedling, vegetative and reproductive stages as compared to wild-type (WT) plants. Moreover, A10-Ds-RFP6 revealed effective antioxidant systems resulting in decreased accumulation of reactive oxygen species and delayed stress symptoms compared to WT plants. Reduced accumulation of malondialdehyde with concomitant increase in proline and soluble sugars in A10-Ds-RFP6 line further endorse its improved stress tolerance levels. Furthermore, A10-Ds-RFP6 disclosed enhanced plant water content, photosynthetic efficiency, stomatal conductance, water use efficiency and maximum quantum yield compared to WT plants. TAIL and qRT-PCR analyses of AT rice line revealed the integration site of Ds element in the genome and increased expression levels of CDC48 and acetyltransferase genes involved in various aspects of plant development and stress tolerance. As such, the promising AT line plausibly serve as a rare genetic resource for fortifying stress tolerance and productivity traits of elite rice cultivars.

Generation of Marker-Free Transgenic Rice Resistant to Rice Blast Disease Using Ac/Ds Transposon-Mediated Transgene Reintegration System.

Rice blast is one of the most serious diseases of rice and a major threat to rice production. Breeding disease-resistant rice is one of the most economical, safe, and effective measures for the control of rice blast. As a complement to traditional crop breeding, the transgenic method can avoid the time-consuming process of crosses and multi-generation selection. In this study, maize (Zea mays) Activator (Ac)/Dissociation (Ds) transposon vectors carrying green fluorescent protein (GFP) and red fluorescent protein (mCherry) genetic markers were used for generating marker-free transgenic rice. Double fluorescent protein-aided counterselection against the presence of T-DNA was performed together with polymerase chain reaction (PCR)-based positive selection for the gene of interest (GOI) to screen marker-free progeny. We cloned an RNAi expression cassette of the rice Pi21 gene that negatively regulates resistance to rice blast as a GOI into the Ds element in the Ac/Ds vector and obtained marker-free T1 rice plants from 13 independent transgenic lines. Marker-free and Ds/GOI-homozygous rice lines were verified by PCR and Southern hybridization analysis to be completely free of transgenic markers and T-DNA sequences. qRT-PCR analysis and rice blast disease inoculation confirmed that the marker-free transgenic rice lines exhibited decreased Pi21 expression levels and increased resistance to rice blast. TAIL-PCR results showed that the Ds (Pi21-RNAi) transgenes in two rice lines were reintegrated in intergenic regions in the rice genome. The Ac/Ds vector with dual fluorescent protein markers offers more reliable screening of marker-free transgenic progeny and can be utilized in the transgenic breeding of rice disease resistance and other agronomic traits.

Calculation of atomic properties of superheavy elements Z=110–112 and their ions

We calculate the spectra, electric dipole transition rates and isotope shifts of the super heavy elements Ds (Z=110), Rg (Z=111) and Cn (Z=112) and their ions. These calculations were performed using a recently developed, efficient version of the ab initio configuration interaction combined with perturbation theory to treat distant effects. The successive ionization potentials of the three elements are also calculated and compared to lighter elements.

Development of a large population of activation‐tagged mutants in an elite indica rice variety

AbstractIn this study, we have generated more than 12,000 activation‐tagged mutants in a high‐yielding indica rice variety, 'BPT 5204', employing maize Ac/Ds system. Different transgenic plants obtained were analysed based on expression patterns of green fluorescence protein (GFP), red fluorescence protein (RFP), herbicide (Basta) tolerance and molecular analyses. T1 seeds of pSQ5 and pSQ5‐bar transgenics, when germinated separately on hygromycin (50 mg/L) and phosphinothricin (5 mg/L) containing medium, revealed a segregation of 3 tolerant : 1 susceptible plants. The germinal transposition frequency of Ds element in different T2 progeny of rice plants was found to be about 18.0%. Different stable tagged mutants exhibited marked increases in plant height, number of tillers, leaf size, panicle size, seed size and number of grains per plant. The overall results indicate that the genes associated with these traits are upregulated by the enhancer element in activation‐tagged mutants. As such, the various tagged mutant lines appear promising and serve as a valuable genetic resource for identification of key genes determining different agronomic traits of rice.

Isolation and characterization of genes related to sheath blight resistance via the tagging of mutants in rice

Sheath blight disease (ShB) in rice is caused by Rhizoctonia solani. However, there have been no major genes identified from wild rice relatives and cultivated rice that encode resistance to R. solani. In this study, 300 Ds tagging mutants were generated via tissue culture regeneration methods from a Ds (dissociation) insertion line, and R. solani AG1-IA was inoculated to isolate the resistant mutants. The starter line that was homozygous (Ds-s) with a single Ds insertion in chromosome 1 exhibited a similar response to ShB as the non-transgenic plants. A Southern blot analysis showed that the Ds element was actively transposed in 300 R1 lines generated from Ds-s, and R2 plants were generated by selfing using 300 R1 lines with Ds insertions. Out of 300 R2 lines, two lines displayed susceptibility, and two lines exhibited strong resistance to ShB. In addition, 23 mutant lines displayed resistant symptoms, and the remaining 273 lines showed no differences compared to the ShB-susceptible wild-type control plants. Further examination revealed that the Ds gene was inserted at the second intron of either the PHYTOCHROME B (PHYB) or LAZY1 gene in two strong resistant mutants. We showed that the ethylene signaling genes (EIL1, EIL2, EIN2, and ERF63), jasmonic acid synthesis gene (LOX2), and salicylic acid signaling gene PBZ1 were up-regulated in the phyB mutants compared with the wild-type control that is susceptible to ShB. Further genetic study using EIL1 RNAi and EIL1 overexpression plants revealed that EIL1 positively regulates the resistance of rice to ShB. Overall, our analyses provided a basis for the identification of ShB resistance genes and the realization that PHYB negatively regulates the resistance of rice to ShB via the suppression of ethylene signaling.

Mapping of transgenic alleles in soybean using a nanopore-based sequencing strategy.

Transgenic technology was developed to introduce transgenes into various organisms to validate gene function and add genetic variations >40 years ago. However, the identification of the transgene insertion position is still challenging in organisms with complex genomes. Here, we report a nanopore-based method to map the insertion position of a Ds transposable element originating in maize in the soybean genome. In this method, an oligo probe is used to capture the DNA fragments containing the Ds element from pooled DNA samples of transgenic soybean plants. The Ds element-enriched DNAs are then sequenced using the MinION-based platform of Nanopore. This method allowed us to rapidly map the Ds insertion positions in 51 transgenic soybean lines through a single sequencing run. This strategy is high throughput, convenient, reliable, and cost-efficient. The transgenic allele mapping protocol can be easily translated to other eukaryotes with complex genomes.

An Efficient System for Ds Transposon Tagging in Brachypodium distachyon.

Transposon tagging is a powerful tool that has been widely applied in several species for insertional mutagenesis in plants. Several efforts have aimed to create transfer-DNA (T-DNA) insertional mutant populations in Brachypodium distachyon, a monocot plant used as a model system to study temperate cereals, but there has been a lack of research aimed at using transposon strategies. Here, we describe the application of a maize (Zea mays) Dissociation (Ds) transposon tagging system in B distachyon The 35S::AcTPase cassette and Ds element were constructed within the same T-DNA and transformed into B distachyon plants. The Ds element was readily transposed to other chromosomes or to the same chromosome under the function of Activator (Ac) transposase. Through homologous chromosome synapsis, recombination, and segregation, the Ds element separated from the Ac element. We selected stable Ds-only plants using G418 and GFP assays and analyzed 241 T0 lines, some of which were highly efficient at producing Ds-only progeny. Through thermal asymmetric interlaced PCR, we isolated 710 independent Ds flanking sequences from Ds-only plants. Furthermore, we identified a large collection of mutants with visible developmental phenotypes via this transposon tagging system. The system is relatively simple and rapid in comparison to traditional T-DNA insertion strategies, because once efficiency lines are obtained they can be reused to generate more lines from nontransposed plants without the use of time-consuming tissue culture steps.

Registration of the Barley Transposon‐Tagged Population II: Sixty‐One Lines Each Characterized for Ds Insertion Sites

The USDA–ARS has developed and released a transposon‐tagging barley (Hordeum vulgare L.) population comprising 61 lines: TNPs 1, 3, 6, 11, 13, 18, 19, 22, 24, 26–35, 32B, 39–41, 48, 52, 53, 66–69, 71, 74, 79–83, 90, 92–94, 99, 100, 103, 112, 115, 116A, 116B, 117–120, 125, 130, 132, 141, 142, 144, 230, 231, and 234 (Reg. Nos. GS‐83–GS‐143; PIs 687803–687863). Each line is homozygous for a single modified Ds element encoding bar (Ds‐bar) insertion at a different genomic location, except for TNP 120, which has two insertions. The ∼3.6 kb Ds‐bar element is a modified maize (Zea mays L.) Dissociation (Ds) element containing a bar expression cassette. Two of lines (TNP 32B and TNP 48) derive from primary Ds (PDS) transpositions resulting from biolistic co‐introduction of Ds‐bar and maize Ac transposase (AcT) into ‘Golden Promise’. The rest contain either secondary or tertiary transpositions generated by remobilizing Ds‐bar via hybridization of AcT‐expressing Golden Promise plants with, respectively, PDS lines containing primary transpositions or TNP lines containing secondary transpositions. Each line was characterized for the 5′ and/or 3′ sequences flanking the Ds‐bar insertion. Insertions that interrupt native genes or regulatory elements likely will alter or abolish their function, and these lines are expected to be useful for the study of the biological roles of such genes or regulatory sequences. Most of these lines can also be used as parents for the creation of additional lines with novel transpositions of Ds‐bar.

Characterization of maize leaf pyruvate orthophosphate dikinase using high throughput sequencing.

In C4 photosynthesis, pyruvate orthophosphate dikinase (PPDK) catalyzes the regeneration of phosphoenolpyruvate in the carbon shuttle pathway. Although the biochemical function of PPDK in maize is well characterized, a genetic analysis of PPDK has not been reported. In this study, we use the maize transposable elements Mutator and Ds to generate multiple mutant alleles of PPDK. Loss-of-function mutants are seedling lethal, even when plants were grown under 2% CO2 , and they show very low capacity for CO2 assimilation, indicating C4 photosynthesis is essential in maize. Using RNA-seq and GC-MS technologies, we examined the transcriptional and metabolic responses to a deficiency in PPDK activity. These results indicate loss of PPDK results in downregulation of gene expression of enzymes of the C4 cycle, the Calvin cycle, and components of photochemistry. Furthermore, the loss of PPDK did not change Kranz anatomy, indicating that this metabolic defect in the C4 cycle did not impinge on the morphological differentiation of C4 characters. However, sugar metabolism and nitrogen utilization were altered in the mutants. An interaction between light intensity and genotype was also detected from transcriptome profiling, suggesting altered transcriptional and metabolic responses to environmental and endogenous signals in the PPDK mutants.

Maize Transposable Elements Ac/Ds as Insertion Mutagenesis Tools in Candida albicans.

In nonmodel systems, genetic research is often limited by the lack of techniques for the generation and identification of gene mutations. One approach to overcome this bottleneck is the application of transposons for gene tagging. We have established a two-element transposon tagging system, based on the transposable elements Activator (Ac)/Dissociation (Ds) from maize, for in vivo insertion mutagenesis in the fungal human pathogen Candida albicans. A nonautonomous Ds transposon carrying a selectable marker was constructed into the ADE2 promoter on chromosome 3 and a codon usage-adapted Ac transposase gene was inserted into the neutral NEUT5L locus on chromosome 5. In C. albicans cells expressing the transposase, the Ds element efficiently excised and reintegrated elsewhere in the genome, which makes the Ac/Ds transposons promising tools for saturating insertion mutagenesis in clinical strains of C. albicans.

Standardization of Agrobacterium mediated genetic transformation in Indica rice cv BPT-5204

The BPT-5204 genotype from Indica rice cultivar (cv) is recalcitrant and showed low transformation frequency compare to japonica rice cv. Here we have optimized the efficient transformation protocol to minimize the time scale and enhance the transformation frequency by altering the key parameters like, acetosyringone (AS) concentration, optical density of bacterial culture and co-cultivation time. Highly proliferated 21 days old Scutellum derived embryogenic calli were infected with Agrobacterium tumefaciens harbouring pCAMBIA2300-Ds-En-Bar binary vector. T-DNA contains tetrameric CaMV35S enhancer elements along with bar gene which embedded between the transposable Ds element. At 0.5 OD600nm of Agrobacterium culture and co-cultivation for 2 days on MS co-cultivation medium containing 100 μM acetosyringone proved to be optimal and attained 6.2 % of transformation efficiency. The transformed calli and regenerated plantlets were proliferated on Murashige and Skoog (MS) medium containing phosphinothricin (PPT). Polymerase chain reaction (PCR) confirmed that intact T-DNA was successfully integrated in the rice genome. This protocol can be employed to develop transgenic rice plants with gain of functional mutagenesis.

Опыт применения методов математической картографии в космологии

The experience of mathematical modeling of the 3D-sphere in the 4D-space and projecting it by mathematical cartography methods in the 3D-Euclidian space is presented. The problem is solved by introduction of spherical coordinates for the 3D-sphere and their transformation into the rectangular coordinates, using the mathematical cartography methods. The mathematical relationship for calculating the length distortion mp(s) of the ds linear element when projecting the 3D-sphere from the 4-dimensional Euclidian space into three-dimensional Euclidian space is derived. Numerical examples, containing the modeling of the ds small linear element by spherical coordinates of 3D-sphere, projecting this sphere into the 3D-Euclidian space and length of ds calculating by means of its projection dL and size of distortion mp(s) are solved. Based on the model of the Universe known in cosmology as the 3D-sphere, the hypothesis of connection between distortion mp(s) and the known observed effects Redshift and Microwave Background Radiation is considered.

Maize defective kernel mutant generated by insertion of a Ds element in a gene encoding a highly conserved TTI2 cochaperone

We have used the newly engineered transposable element Dsg to tag a gene that gives rise to a defective kernel (dek) phenotype. Dsg requires the autonomous element Ac for transposition. Upon excision, it leaves a short DNA footprint that can create in-frame and frameshift insertions in coding sequences. Therefore, we could create alleles of the tagged gene that confirmed causation of the dek phenotype by the Dsg insertion. The mutation, designated dek38-Dsg, is embryonic lethal, has a defective basal endosperm transfer (BETL) layer, and results in a smaller seed with highly underdeveloped endosperm. The maize dek38 gene encodes a TTI2 (Tel2-interacting protein 2) molecular cochaperone. In yeast and mammals, TTI2 associates with two other cochaperones, TEL2 (Telomere maintenance 2) and TTI1 (Tel2-interacting protein 1), to form the triple T complex that regulates DNA damage response. Therefore, we cloned the maize Tel2 and Tti1 homologs and showed that TEL2 can interact with both TTI1 and TTI2 in yeast two-hybrid assays. The three proteins regulate the cellular levels of phosphatidylinositol 3-kinase-related kinases (PIKKs) and localize to the cytoplasm and the nucleus, consistent with known subcellular locations of PIKKs. dek38-Dsg displays reduced pollen transmission, indicating TTI2's importance in male reproductive cell development.

Arabidopsis thaliana G2-LIKE FLAVONOID REGULATOR and BRASSINOSTEROID ENHANCED EXPRESSION1 are low-temperature regulators of flavonoid accumulation.

Flavonoid synthesis is predominantly regulated at the transcriptional level through the MYB-basic helix-loop-helix (bHLH)-WD40 (MBW) (MYB: transcription factor of the myeloblastosis protein family, WD40: tanscription factor with a short structural motif of 40 amino acids which terminates in an aspartic acid-tryptophan dipeptide) complex, and responds to both environmental and developmental stimuli. Although the developmental regulation of flavonoid accumulation in Arabidopsis thaliana has been examined in great detail, the response of the flavonoid synthesis pathway to abiotic stress (particularly low temperature) remains unclear. A screen of a Dissociation element (Ds) transposon-induced mutation collection identified two lines which exhibited an altered profile of phenylpropanoid accumulation following exposure to low-temperature stress. One of the mutated genes (BRASSINOSTEROID ENHANCED EXPRESSION1 (BEE1)) encoded a brassinosteroid enhanced expression transcription factor, while the other (G2-LIKE FLAVONOID REGULATOR (GFR)) encoded a G2-like flavonoid regulator. Phenylpropanoid-targeted analysis was performed using high-performance LC-MS, and gene expression analysis using quantitative reverse transcription-PCR. In both mutants, the accumulation of quercetins and scopolin was reduced under low-temperature growing conditions, whereas that of anthocyanin was increased. BEE1 and GFR were both shown to negatively regulate anthocyanin accumulation by inhibiting anthocyanin synthesis genes via the suppression of the bHLH (TRANSPARENT TESTA8 (TT8) and GLABROUS3 (GL3)) and/or the MYB (PRODUCTION OF ANTHOCYANIN PIGMENTS2 (PAP2)) components of the MBW complex. Our results provide new insight into the regulatory control of phenylpropanoid metabolism at low temperatures, and reveal that BEE1 and GFR act as important components of the signal transduction chain.

Generation and Analysis of Transposon Ac/Ds-Induced Chromosomal Rearrangements in Rice Plants.

Closely-located transposable elements (TEs) have been known to induce chromosomal breakage and rearrangements via alternative transposition. To study genome rearrangements in rice, an Ac/Ds system has been employed. This system comprises an immobile Ac element expressed under the control of CaMV 35S promoter, and a modified Ds element. A starter line carried Ac and a single copy of Ds at the OsRLG5 (Oryza sativa receptor-like gene 5). To enhance the transpositional activity, seed-derived calli were cultured and regenerated into plants. Among 270 lines regenerated from the starter, one line was selected that contained a pair of inversely-oriented Ds elements at the OsRLG5 (Oryza sativa receptor-like gene 5). The selected line was again subjected to tissue culture to obtain a regenerant population. Among 300 regenerated plants, 107 (36 %) contained chromosomal rearrangements including deletions, duplications, and inversions of various sizes. From 34 plants, transposition mechanisms leading to such genomic rearrangements were analyzed. The rearrangements were induced by sister chromatid transposition (SCT), homologous recombination (HR), and single chromatid transposition (SLCT). Among them, 22 events (65 %) were found to be transmitted to the next generation. These results demonstrate a great potential of tissue culture regeneration and the Ac/Ds system in understanding alternative transposition mechanisms and in developing chromosome engineering in plants.

Diverse chromosomal rearrangements induced by Ac/Ds at the OsRLG5 locus in regenerated rice plants

Closely-located transposable elements (TEs) can induce chromosomal breakage and rearrangements via alternative transposition (AT) reactions. Our previous study showed that diverse chromosomal rearrangements were induced by two inversely-oriented Ds elements at the OsRLG5 (Oryza sativa receptor-like kinase gene 5) locus in regenerated rice plants. Here, several novel chromosomal rearrangements were identified in a population of tissue culture regenerants, and their proposed Ac/Ds-transposition mechanisms were discussed. In the first type of event, AT was induced by the same Ds element on each of two sister chromatids and resulted in the inversion of genomic DNA flanking the Ds element. In the second type of event, DNA segments of the inter-transposon segment (ITS) region were deleted or inverted. This novel local rearrangement likely resulted from an AT reaction of two directly-oriented Ds elements located on the same chromatid. The 5' and 3' termini of two Ds elements were re-inserted into two different sites inside the ITS, which generated the subsequent deletion and inversion. In the third type of event, two inversely-oriented Ds elements induced homologous recombination and chromosomal translocation. Together, these results showed the diversity of Ac/Ds-mediated chromosomal rearrangements and demonstrated the utility of the experimental system for examining the mechanisms underlying Ac/Ds AT reactions.

Behavior of a modified Dissociation element in barley: a tool for genetic studies and for breeding transgenic barley

Maize-derived sequences from the transposable elements Activator (Ac) and Dissociation (Ds) have enabled studies of gene function via transposon tagging. The characteristics of modified, transgene-containing Ds elements constructed for some of these studies have demonstrated their ability to resolve complex loci, separate transgenes from marker genes and vector sequences, and to support high and heritable levels of transgene expression. To most efficiently design breeding schemes for developing transgenic populations via Ds-mediated transposition, detailed knowledge of the dynamics and characteristics of transposition in barley is necessary. Examination of a barley transposon tagging population (n = 4,954) derived from crosses of lines containing Ds-bar insertions to lines expressing Ac transposase showed that the frequencies of transposition from eight original Ds-bar loci ranged from 5 to 41 % among F2 individuals. Sequence analysis of Ds-bar terminal sequences and of flanking genomic sequences for 107 F2 and F3 individuals indicated precise integrations. Analysis of 173 flanking sequences derived from these populations and from previously produced populations, primarily using sequence-based methods, enabled the mapping of 159 to a specific chromosome and 136 to specific map locations. Of the 156 DsT loci that could be located to specific contigs, most were located in gene-rich areas and approximately 40 % were either in or near (within 1 kb) expressed sequences or predicted proteins. These data will enable the design of optimal breeding schemes for developing and using Ds-based systems for transposon tagging and for transgene delivery that are specific to barley.