Variety Chinese Spring Research Articles

Analysis of single nucleotide polymorphisms in sequences of Pina and Pinb genes of the diploid wheats Triticum monococcum and T. urartu

Puroindolines (puroindoline a and puroindoline b) are low molecular weight proteins that determine the endosperm texture of grain in the tribes Triticeae and Avenae. The aim of our study was to analyse single nucleotide polymorphisms (SNPs) of the coding sequences of the Pina and Pinb genes of the diploid wheats Triticum monococcum (AmAm) and T. urartu (AA) from the NCBI database in comparison with the reference sequences of the common wheat variety Chinese Spring (CS).For this, 62 sequences of the T. monococcum puroindoline a gene (Pina-Am1), 22 sequences of T. urartu Pina (Pina-A1), 32 sequences of the T. monococcum puroindoline b gene (Pinb-Am1) and 13 sequences of T. urartu Pinb (Pinb-A1) were retrieved from the NCBI database. The sequences of the puroindoline a gene DQ363911.1 of the variety CS (the Pina-D1a allele) and the puroindoline b gene DQ363913.1 of CS (the Pinb-D1a allele) from the NCBI database were used as the reference sequences. The sequences were aligned using MEGA 11. In total, 34 SNPs (13 synonymous and 21 nonsynonymous differences, of which 15 result in radical amino acid substitutions and 6 in conservative ones) were identified in the total sample of 84 diploid wheat Pina sequences, some of which were observed in all sequences and some were rare. Among the 45 Pinb sequences, there were 36 SNPs, but, unlike the Pina gene, synonymous substitutions prevailed (22); 7 substitutions led to radical amino acid substitutions and 7 to conservative ones. Substitutions in the sequences of the puroindoline genes relative to the CS genes can be divided into those fixed in both diploid wheat species, those fixed in T. urartu and polymorphic in T. monococcum, and species-specific ones. Significant differences in the frequencies of alternative nucleotides at certain positions (81, 318, 322 and 384 of Pina and 135 and 359 of Pinb) were found between the wild einkorn wheat T. monococcum ssp. aegilopoides and the cultivated wheat T. monococcum ssp. monococcum.

Production of omega-5 gliadin monoclonal antibodies for allergenic evaluation of WDEIA-causing wheat varieties

In allergic individuals, ingestion of wheat can lead to wheat-dependent exercise-induced anaphylaxis (WDEIA). Many studies have been conducted to find WDEIA allergen–deficient wheat, including by generating omega-5 gliadin antibodies. However, the reported antibodies have not been specific enough to detect omega-5 gliadins encoded on the 1B chromosome. In this study, we generated monoclonal antibodies against the major allergens causing WDEIA, omega-5 gliadins. Using these antibodies (mono-O5B-1C10), we assessed accumulation of omega-5 gliadins in wild-type and nullisomic-tetrasomic (NT) lines of the wheat (Triticum aestivum) varieties Chinese Spring (CS) by one- and two-dimensional gel electrophoresis, followed by Coomassie blue staining or immunoblotting with mono-O5B-1C10. We also tested mono-O5B-1C10 for major omega-5 gliadins in various wheat germplasms. Our results thus demonstrate the specificity of mono-O5B-1C10 for major omega-5 gliadins and potentially useful for identifying of omega-5 gliadin–deficient wheat varieties that should not cause WDEIA.

TRNA-derived fragments from wheat are potentially involved in susceptibility to Fusarium head blight

BackgroundFusarium head blight (FHB) caused by Fusarium graminearum is a devastating fungal disease of wheat. The mechanism underlying F. graminearum-wheat interaction remains largely unknown. tRNA-derived fragments (tRFs) are RNase-dependent small RNAs derived from tRNAs, and they have not been reported in wheat yet, and whether tRFs are involved in wheat-F. graminearum interactions remains unknown.ResultsHerein, small RNAs from the spikelets inoculated with F. graminearum and mock from an FHB-susceptible variety Chinese Spring (CS) and an FHB-resistant variety Sumai3 (SM) were sequenced respectively. A total of 1249 putative tRFs were identified, in which 15 tRFs was CS-specific and 12 SM-specific. Compared with mock inoculation, 39 tRFs were significantly up-regulated across both wheat varieties after F. graminearum challenge and only nine tRFs were significantly down-regulated. tRFGlu, tRFLys and tRFThr were dramatically induced by F. graminearum infection, with significantly higher fold changes in CS than those in SM. The expression patterns of the three highly induced tRFs were further validated by stem-loop qRT-PCR. The accumulation of tRFs were closely related to ribonucleases T2 family members, which were induced by F. graminearum challenge. The tRFs’ targets in host were predicted and were validated by RNA sequencing.ConclusionIntegrative analysis of the differentially expressed tRFs and their candidate targets indicated that tRFGlu, tRFLys and tRFThr might negatively regulate wheat resistance to FHB. Our results unvealed the potential roles of tRFs in wheat-F. graminearum interactions.

Comprehensive speed breeding: a high-throughput and rapid generation system for long-day crops.

Breeding cycle time largely determines the efficiency of crop genetic improvement. To accelerate the generation progress, Watson et al. (2018) proposed a concept of 'speed breeding (SB)' by extending the photoperiod and increasing the light intensity during plant growth. However, there have been few reports on the successful application of SB in semi-winter and winter long-day crops. Here, we propose a comprehensive speed breeding (CSB) system for the rapid generation and high-throughput culture of long-day crops, which can accomplish 4.5 generations for both semi-winter canola and winter wheat per year. With the aid of extra far-red light, three and 5.5 generations can be accomplished for the typical winter and semi-winter type canola. CSB also exhibits high efficiency in spring type canola, and can achieve up to 6.5 and 5.5 generations with or without extra far-red light, respectively. This strategy is expected to greatly accelerate gene pyramiding of superior alleles, screening of recombinants for QTL mapping and functional genomics research by rapid purification of multiple mutated alleles.

Proteomics unravels new candidate genes of Dasypyrum villosum for improving wheat quality

Wheat is one of the most widely grown and important food crops in the world, providing approximately 20% of the food energy and protein produced for human consumption. The progress of wheat breeding is seriously restricted by the narrow genetic basis of common wheat germplasms. Dasypyrum villosum, a wild grass species that is commonly used in wheat improvement, has many excellent traits such as disease resistance, drought resistance, cold resistance, strong tillering ability, and processing quality. In this study, we compared and analyzed the cultivated wheat variety Chinese Spring (CS) and D. villosum using comparative proteomics. A total of 883 different abundant proteins (DAPs) were identified. Some of these different abundant proteins are associated with defense and stress, such as the Gα subunit, zinc finger protein family, PR1, HSP family, LEA protein, and serpin family. And a total of 24 different abundant proteins are gluten proteins. There are also 24 different abundant proteins associated with starch and sucrose metabolism. These results will provide potential candidate genes and a foundation for further research on resistance and quality for wheat genetics and breeding. SignificanceProteins are the direct functional molecules of living organisms. It is of great significance to study the function of plant related genes from the perspective of protein. In this study, proteomics methods based on iTRAQ were used to compare the proteomic differences between wheat varieties Chinese Spring (CS) and D. villosum. The results provide novel insight into improving the quality of wheat. It is helpful to search for potential candidate genes for improving wheat quality and elucidate the molecular mechanisms associated with these genes.

CSCS: a chromatin state interface for Chinese Spring bread wheat.

The online version contains supplementary material available at 10.1007/s42994-021-00048-z.

A Major Locus on Wheat Chromosome 7B Associated With Late-Maturity α-Amylase Encodes a Putative ent-Copalyl Diphosphate Synthase

Many wheat varieties have the potential to develop unacceptably high levels of α-amylase in the grains if exposed to a cool temperature shock or simply cool temperature during the early to middle stages of grain filling. This phenomenon is referred to as late maturity α-amylase (LMA). The enzyme persists in the grain until harvest and may result in wheat with a low Falling Number that does not meet receival and export specifications. Resistance to LMA is therefore a valuable target for wheat breeders and wheat industries in general. Genetic evidence implicating a locus on the long arm of chromosome 7B in variation in LMA phenotype was confirmed in this investigation. Through intensive fine-mapping an ent-copalyl diphosphate synthase (CPS), hitherto named LMA-1, was identified as the likely candidate gene associated with variation in LMA phenotype. Single Nucleotide Polymorphisms (SNPs) within the LMA-1 coding sequence of Chinese Spring, Maringa and Halberd result in either prematurely terminated or functionally altered proteins that are associated with useful levels of resistance to LMA. LMA-1 transcripts detected in de-embryonated grain tissue from around 15 days after anthesis, several days before the synthesis of α-amylase, were low in the resistant varieties Chinese Spring and Maringa compared with LMA susceptible genotype Spica. This was associated with a dramatic reduction in the concentrations of intermediates in the gibberellin biosynthesis pathway such as GA19, evidence that LMA-1 was functioning as CPS in the gibberellin biosynthesis pathway. A survey of a large collection of Australian and international wheat varieties distinguished 9 major haplotypes at the LMA-1 locus. Generally, within classes, there was notable variation for LMA phenotype and evidence for genotypes whose resistance is presumed to be due to genetic loci located elsewhere on the wheat genome. Further investigation is required to characterize the sequence of steps between LMA-1 and α-amylase synthesis as well as to gain a better understanding of the role and potential impact of other genetic loci. Diagnostic markers for sources of resistance and SNP variation reported in this study should assist breeders to deploy resistance associated with LMA-1 variants in breeding programs.

In-silico prediction of novel genes responsive to drought and salinity stress tolerance in bread wheat (Triticum aestivum).

Common wheat (Triticum aestivum) is the most widely grown cereal crop and is cultivated extensively in dry regions. Water shortage, resulting from either drought or salinity, leads to slow growth and loss of wheat yield. In order to predict new genes responsive to the drought and salt stresses in wheat, 6,717 expressed sequence tags (ESTs), expressed in drought and salinity stress conditions were collected from the National Center for Biotechnology Information (NCBI). The downloaded ESTs were clustered and assembled into 354 contigs; 14 transcription factor families in 29 contigs were identified. In addition, 119 contigs were organized in five enzyme classes. Biological functions were obtained for only 324 of the 354 contigs using gene ontology. In addition, using Kyoto Encyclopedia of Genes and Genomes database, 191 metabolic pathways were identified. The remaining contigs were used for further analysis and the search for new genes responsive to drought and salt stresses. These contigs were mapped on the International Wheat Genome Sequencing Consortium RefSeq v1.0 assembly, the most complete version of the reference sequence of the bread wheat variety Chinese Spring. They were found to have from one to three locations on the subgenomes A, B, and D. Full-length gene sequences were designed for these contigs, which were further validated using promoter analysis. These predicted genes may have applications in molecular breeding programs and wheat drought and salinity research.

Genomic, Biochemical, and Modeling Analyses of Asparagine Synthetases from Wheat.

Asparagine synthetase activity in cereals has become an important issue with the discovery that free asparagine concentration determines the potential for formation of acrylamide, a probably carcinogenic processing contaminant, in baked cereal products. Asparagine synthetase catalyses the ATP-dependent transfer of the amino group of glutamine to a molecule of aspartate to generate glutamate and asparagine. Here, asparagine synthetase-encoding polymerase chain reaction (PCR) products were amplified from wheat (Triticum aestivum) cv. Spark cDNA. The encoded proteins were assigned the names TaASN1, TaASN2, and TaASN3 on the basis of comparisons with other wheat and cereal asparagine synthetases. Although very similar to each other they differed slightly in size, with molecular masses of 65.49, 65.06, and 66.24 kDa, respectively. Chromosomal positions and scaffold references were established for TaASN1, TaASN2, and TaASN3, and a fourth, more recently identified gene, TaASN4. TaASN1, TaASN2, and TaASN4 were all found to be single copy genes, located on chromosomes 5, 3, and 4, respectively, of each genome (A, B, and D), although variety Chinese Spring lacked a TaASN2 gene in the B genome. Two copies of TaASN3 were found on chromosome 1 of each genome, and these were given the names TaASN3.1 and TaASN3.2. The TaASN1, TaASN2, and TaASN3 PCR products were heterologously expressed in Escherichia coli (TaASN4 was not investigated in this part of the study). Western blot analysis identified two monoclonal antibodies that recognized the three proteins, but did not distinguish between them, despite being raised to epitopes SKKPRMIEVAAP and GGSNKPGVMNTV in the variable C-terminal regions of the proteins. The heterologously expressed TaASN1 and TaASN2 proteins were found to be active asparagine synthetases, producing asparagine and glutamate from glutamine and aspartate. The asparagine synthetase reaction was modeled using SNOOPY® software and information from the BRENDA database to generate differential equations to describe the reaction stages, based on mass action kinetics. Experimental data from the reactions catalyzed by TaASN1 and TaASN2 were entered into the model using Copasi, enabling values to be determined for kinetic parameters. Both the reaction data and the modeling showed that the enzymes continued to produce glutamate even when the synthesis of asparagine had ceased due to a lack of aspartate.

New Oligonucleotide Probes for ND-FISH Analysis to Identify Barley Chromosomes and to Investigate Polymorphisms of Wheat Chromosomes.

Oligonucleotide probes that can be used for non-denaturing fluorescence in situ hybridization (ND-FISH) analysis are convenient tools for identifying chromosomes of wheat (Triticum aestivum L.) and its relatives. New oligonucleotide probes, Oligo-HvT01, Oligo-pTa71-1, Oligo-s120.1, Oligo-s120.2, Oligo-s120.3, Oligo-275.1, Oligo-275.2, Oligo-k566 and Oligo-713, were designed based on the repetitive sequences HVT01, pTa71, pTa-s120, pTa-275, pTa-k566 and pTa-713. All these probes can be used for ND-FISH analysis and some of them can be used to detect polymorphisms of wheat chromosomes. Probes Oligo-HvT01, Oligo-pTa71-1, Oligo-s120.3, Oligo-275.1, Oligo-k566 and Oligo-713 can, respectively, replace the roles of their original sequences to identify chromosomes of some barley (Hordeum vulgare ssp. vulgare) and the common wheat variety Chinese Spring. Oligo-s120.1, Oligo-s120.2 and Oligo-275.2 produced different hybridization patterns from the ones generated by their original sequences. In addition, Oligo-s120.1, Oligo-s120.2 and Oligo-s120.3, which were derived from pTa-s120, revealed different signal patterns. Likewise, Oligo-275.1 and Oligo-275.2, which were derived from pTa-275, also displayed different hybridization patterns. These results imply that differently arranged or altered structural statuses of tandem repeats might exist on different chromosome regions. These new oligonucleotide probes provide extra convenience for identifying some wheat and barley chromosomes, and they can display polymorphisms of wheat chromosomes.

Identification and molecular characterization of one novel 1SPl-encoded s-type low molecular weight glutenin B-subunit from 1Sl(1B) substitution line of wheat variety Chinese Spring (Triticum aestivum)

Abstract(2

Identification of drought stress related proteins from 1Sl(1B) chromosome substitution line of wheat variety Chinese Spring.

BackgroundWheat, one of the most important crops, has a detrimental effect on both yield and quality under drought stress. As our preliminary experiment showed that the Chinese Spring wheat-Aegilops longissima chromosome substitution line CS-1Sl (1B) had a better drought tolerance than CS, the substitution line CS-1Sl(1B) was used to identify drought stress related proteins by means of a comparative proteome approach in this work. Our present study aimed to explore the gene resources for drought resistance in 1Sl genome.ResultOur results showed that drought stress induced downregulation of relative water and chlorophyll contents and the upregulation of proline content, and further influencing grain filling shortening and significant decrease of plant height, B-type starch granule numbers, grain number and weight. In total, 25 grain albumin and globulin protein spots were found to be specifically encoded by the 1Sl chromosome. In addition, 17 protein spots respected 13 unique proteins were identified by MALDI-TOF/TOF MS, which were mainly involved in adverse defense and gluten quality. Among them, ascorbate peroxidase, serpin-Z2B and alpha-amylase/trypsin inhibitor were upregulated under drought stress. These proteins play important roles in plant drought defenses through various metabolic pathways.ConclusionOur results indicate that the 1Sl chromosome of Aegilops longissima has potential gene resources that could be useful for improving wheat drought resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-016-0134-x) contains supplementary material, which is available to authorized users.

Pistillody mutant reveals key insights into stamen and pistil development in wheat (Triticum aestivum L.).

BackgroundThe pistillody mutant wheat (Triticum aestivum L.) plant HTS-1 exhibits homeotic transformation of stamens into pistils or pistil-like structures. Unlike common wheat varieties, HTS-1 produces three to six pistils per floret, potentially increasing the yield. Thus, HTS-1 is highly valuable in the study of floral development in wheat. In this study, we conducted RNA sequencing of the transcriptomes of the pistillody stamen (PS) and the pistil (P) from HTS-1 plants, and the stamen (S) from the non-pistillody control variety Chinese Spring TP to gain insights into pistil and stamen development in wheat.ResultsApproximately 40 Gb of processed reads were obtained from PS, P, and S. De novo assembly yielded 121,210 putative unigenes, with a mean length of 695 bp. Among these high-quality unigenes, 59,199 (48.84%) had at least one significant match with an existing gene model. A total of 23, 263, and 553 differentially expressed genes were identified in PS vs. P, PS vs. S, and P vs. S, respectively, with differences in expression greater than five-fold. Among the differentially expressed genes, 206 were highly correlated with stamen and pistil development. These genes include WM27B, DL, YAB1, YABBY4, WM 5, CER 1, and WBLH1, which have been implicated in flower development. The expression patterns of 25 differentially expressed genes were confirmed through quantitative real-time reverse transcription PCR.ConclusionsAnalysis of this transcriptome resource enabled us to characterize gene expression profiles, examine differential gene expression, and produce a candidate gene list related to wheat stamen and pistil development. This work is significant for the development of genomic resources for wheat, and provides important insights into the molecular mechanisms of wheat stamen and pistil development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1453-0) contains supplementary material, which is available to authorized users.

Thinopyrum ponticum Chromatin-Integrated Wheat Genome Shows Salt-Tolerance at Germination Stage

A wild wheatgrass, Thinopyrum ponticum (2n = 10x = 70), which exhibits substantially higher levels of salt tolerance than cultivated wheat, was employed to transfer its salt tolerance to common wheat by means of wide hybridization. A highly salt-tolerant wheat line S148 (2n = 42) was obtained from the BC3F2 progenies between Triticum aestivum (2n = 42) and Th. ponticum. In the cross of S148 × salt-sensitive wheat variety Chinese Spring, the BC4F2 seeds at germination stage segregated into a ratio of 3 salt tolerant to 1 salt sensitive, indicating that the salt tolerance was conferred by a dominant gene block. Genomic in situ hybridization analysis revealed that S148 had a single pair of Th. ponticum–T. aestivum translocated chromosomes bearing the salt-tolerance. This is an initial step of molecular breeding for salt-tolerant wheat.

Investigating the Role of Respiration in Plant Salinity Tolerance by Analyzing Mitochondrial Proteomes from Wheat and a Salinity-Tolerant Amphiploid (Wheat × Lophopyrum elongatum)

The effect of salinity on mitochondrial properties was investigated by comparing the reference wheat variety Chinese Spring (CS) to a salt-tolerant amphiploid (AMP). The octoploid AMP genotype was previously generated by combining hexaploid bread wheat (CS) with the diploid wild wheatgrass adapted to salt marshes, Lophopyrum elongatum. Here we used a combination of physiological, biochemical, and proteomic analyses to explore the mitochondrial and respiratory response to salinity in these two genotypes. The AMP showed greater growth tolerance to salinity treatments and altered respiration rate in both roots and shoots. A proteomic workflow of 2D-DIGE and MALDI TOF/TOF mass spectrometry was used to compare the protein composition of isolated mitochondrial samples from roots and shoots of both genotypes, following control or salt treatment. A large set of mitochondrial proteins were identified as responsive to salinity in both genotypes, notably enzymes involved in detoxification of reactive oxygen species. Genotypic differences in mitochondrial composition were also identified, with AMP exhibiting a higher abundance of manganese superoxide dismutase, serine hydroxymethyltransferase, aconitase, malate dehydrogenase, and β-cyanoalanine synthase compared to CS. We present peptide fragmentation spectra derived from some of these AMP-specific protein spots, which could serve as biomarkers to track superior protein variants.

Genetic characterization and mapping of the Rht-1 homoeologs and flanking sequences in wheat

The introgression of Reduced height (Rht)-B1b and Rht-D1b into bread wheat (Triticum aestivum) varieties beginning in the 1960s led to improved lodging resistance and yield, providing a major contribution to the 'green revolution'. Although wheat Rht-1 and surrounding sequence is available, the genetic composition of this region has not been examined in a homoeologous series. To determine this, three Rht-1-containing bacterial artificial chromosome (BAC) sequences derived from the A, B, and D genomes of the bread wheat variety Chinese Spring (CS) were fully assembled and analyzed. This revealed that Rht-1 and two upstream genes were highly conserved among the homoeologs. In contrast, transposable elements (TEs) were not conserved among homoeologs with the exception of intronic miniature inverted-repeat TEs (MITEs). In relation to the Triticum urartu ancestral line, CS-A genic sequences were highly conserved and several colinear TEs were present. Comparative analysis of the CS wheat BAC sequences with assembled Poaceae genomes showed gene synteny and amino acid sequences were well preserved. Further 5' and 3' of the wheat BAC sequences, a high degree of gene colinearity is present among the assembled Poaceae genomes. In the 20kb of sequence flanking Rht-1, five conserved non-coding sequences (CNSs) were present among the CS wheat homoeologs and among all the Poaceae members examined. Rht-A1 was mapped to the long arm of chromosome 4 and three closely flanking genetic markers were identified. The tools developed herein will enable detailed studies of Rht-1 and linked genes that affect abiotic and biotic stress response in wheat.

Proteomic Analysis of Albumins and Globulins from Wheat Variety Chinese Spring and Its Fine Deletion Line 3BS-8

The relationship between chromosome deletion in wheat and protein expression were investigated using Chinese Spring and fine deletion line 3BS-8. Through 2-DE (2-D electrophoresis) analysis, no differentially expressed proteins (DEPs) were found in leaf samples; however, 47 DEPs showed at least two-fold abundance variation (p < 0.05) in matured wheat grains and 21 spots were identified by tandem MALDI-TOF/TOF-MS. Among the identified spots, four were cultivar-specific, including three (spots B15, B16, and B21) in Chinese Spring and one in 3BS-8 (spot B10). Among variety-different DEPs between Chinese Spring and 3BS-8, most spots showed a higher express profile in CS; only four spots showed up-regulated expression tendency in 3BS-8. An interesting observation was that more than half of the identified protein spots were involved in storage proteins, of which 11 spots were identified as globulins. According to these results, we can presume that the encoded genes of protein spots B15, B16, and B21 were located on the chromosome segment deleted in 3BS-8.

RAPD and ISSR-assisted identification and development of three new SCAR markers specific for the Thinopyrum elongatum E (Poaceae) genome

Diploid Thinopyrum elongatum, a wild relative of wheat, contains many agronomically desirable traits and has potential for increasing genetic variability and introducing desirable characters in this crop. Few molecular markers are available for rapid screening of T. elongatum genome segments in the wheat genetic background. We used 36 RAPD primers and 33 ISSR primers to screen for polymorphisms in the common wheat variety Chinese Spring and in T. elongatum. Two RAPD markers and one ISSR marker, designated OPF03(1407), LW10(1487) and UBC841(701), were identified and were specific for the T. elongatum E genome. Three pairs of primers flanking these specific sequences were designed to produce SCAR markers. All three SCAR markers were T. elongatum E genome-specific. Two of these SCAR markers, SCAR(807) and SCAR(577), were present in all seven T. elongatum chromosomes, while SCAR(839) was specific for T. elongatum chromosomes 2E and 3E. These newly developed SCAR markers should be useful for detecting alien genome chromatin or chromosome segments in the genetic background of common wheat.

Genomic analysis of carbon isotope discrimination, photosynthesis rate, stomatal conductance, and grain yield in wheat (Triticum aestivum L.) under water-stressed conditions

Chromosomal substitution lines of wheat variety Timstein (Tim) into the genetic background of variety Chinese Spring (CS) were used to evaluate the chromosomal location of genes controlling carbon isotope discrimination (Δ), photosynthesis rate (PR), stomatal conductance (SC), and grain yield. The experiment was carried out in the field at Shahrekord University Research Station. Considerable variation was observed among the substitution lines and between the parents for all traits. Chinese Spring had smaller values for the characters under study than Timstein. Significant correlations were found for grain yield with PR (r = 0.556) and Δ (r = 0.619). The substitution line CS (Tim2B) was significantly different from CS for Δ (P &lt; 0.01). The substitution of homeologous group 3 chromosomes produced significant differences from the recipient variety for PR. Substitution lines CS (Tim3A), CS (Tim3B), CS (Tim4B), and CS (Tim1D) were significantly different from CS for SC. Genomic comparisons indicated that genome B had higher values of all four characters compared with the A and D genomes. Homeologous effects of genomes were documented for Δ and PR only and not for SC and grain yield.

Recent insertion of a 52-kb mitochondrial DNA segment in the wheat lineage

The assembly of a 1.3-Mb size region of the wheat genome has provided the opportunity to study a recent nuclear mitochondrial DNA insertion (NUMT). In the present study, we have studied two bacterial artificial chromosomes (BACs) and characterized a 52-kb NUMT segment from the tetraploid and hexaploid wheat BAC libraries. The conserved orthologous NUMT regions from tetraploid and hexaploid wheat Langdon and Chinese Spring shared identical gene haplotypes even though mutations (insertions, deletions, and substitutions) had occurred. The 52-kb NUMT was present in hexaploid variety Chinese Spring, but absent in variety Hope, by sequence comparison of their corresponding region. Amplifying the NUMT junctions using a set of the wheat materials including diploid, tetraploid, and hexaploid lines showed that none of the diploid wheat carried the region and only some tetraploid and hexaploid wheat were positive for the NUMT. Age estimation of the NUMT displayed the mean ages of Langdon NUMT and Chinese Spring NUMT to be 378,000 and 416,000years ago, respectively. Reverse transcription PCR and sequencing of the nad7 gene showed 28 C → U RNA editing sites and four partial editing sites, as expected for mitochondrial DNA expression. Specific SNPs discriminated between cDNA from the nucleus and the mitochondria and suggested that the nuclear copy was not expressed. The mitochondrial DNA studied was inserted into the genome quite recently within the wheat lineage and gave rise to the non-coding nuclear nad7 gene. The NUMT segment could be lost and acquired frequently during the wheat evolution.