Mapping of a Recessive Gene for All-Stage Resistance to Stripe Rust in a Wheat Line Derived from Cultivated Einkorn (Triticum monococcum).

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive fungal diseases of wheat. Cultivated einkorn (Triticum monococcum L. ssp. monococcum, 2n = 2x = 14, AmAm), one of the founder crops of agriculture, harbors unexploited genetic sources for wheat improvement. An advanced wheat line, Z15-1949, with 42 chromosomes, selected from the hybrids of Pst-susceptible common wheat cultivar Crocus and resistant T. monococcum accession 10-1, exhibits high resistance to a mixture of the prevalent Chinese Pst races. Genetic analysis on F1, F2, and F2:3 generations of the cross between Z15-1949 and Pst-susceptible common wheat SY95-71 indicated that the resistance of Z15-1949 was conferred by a recessive gene, tentatively designated as YrZ15-1949. This gene was mapped to the short arm of chromosome 7D using the Wheat 55K single nucleotide polymorphism array, flanked by markers KASP-1949-2 and KASP-1949-10 within a 3.3-cM genetic interval corresponding to a 1.12-Mb physical region in the Chinese Spring reference genome V2.0. The gene differs from previously reported Yr genes on 7D based on their physical positions and is probably a novel gene. YrZ15-1949 would be a valuable resource for developing Pst-resistant wheat cultivars, and the linked markers could be used for marker-assisted selection.

Characterization and Mapping of a Rolling Leaf Mutant Allele rlT73 on Chromosome 1BL of Wheat.

Leaf rolling is regarded as an important morphological trait in wheat breeding. Moderate leaf rolling is helpful to keep leaves upright and improve the photosynthesis of plants, leading to increased yield. However, studies on the identification of genomic regions/genes associated with rolling leaf have been reported less frequently in wheat. In this study, a rolling leaf mutant, T73, which has paired spikelets, dwarfism, and delayed heading traits, was obtained from a common wheat landrace through ethyl methanesulfonate mutagenesis. The rlT73 mutation caused an increase in the number of epidermal cells on the abaxial side and the shrinkage of bulliform cells on the adaxial side, leading to an adaxially rolling leaf phenotype. Genetic analysis showed that the rolling leaf phenotype was controlled by a single recessive gene. Further Wheat55K single nucleotide polymorphism array-based bulked segregant analysis and molecular marker mapping delimited rlT73 to a physical interval of 300.29-318.33 Mb on the chromosome arm 1BL in the Chinese Spring genome. We show that a point mutation at the miRNA165/166 binding site of the HD zipper class III transcription factor on 1BL altered its transcriptional level, which may be responsible for the rolling leaf phenotype. Our results suggest the important role of rlT73 in regulating wheat leaf development and the potential of miRNA-based gene regulation for crop trait improvement.

Comparative analysis of Fusarium crown rot resistance in synthetic hexaploid wheats and their parental genotypes.

BACKGROUND: Fusarium crown rot (FCR) is a chronic disease of cereals worldwide. Compared with tetraploid wheat, hexaploid wheat is more resistant to FCR infection. The underlying reasons for the differences are still not clear. In this study, we compared FCR responses of 10 synthetic hexaploid wheats (SHWs) and their tetraploid and diploid parents. We then performed transcriptome analysis to uncover the molecular mechanism of FCR on these SHWs and their parents. RESULTS: We observed higher levels of FCR resistance in the SHWs compared with their tetraploid parents. The transcriptome analysis suggested that multiple defense pathways responsive to FCR infection were upregulated in the SHWs. Notably, phenylalanine ammonia lyase (PAL) genes, involved in lignin and salicylic acid (SA) biosynthesis, exhibited a higher level of expression to FCR infection in the SHWs. Physiological and biochemical analysis validated that PAL activity and SA and lignin contents of the stem bases were higher in SHWs than in their tetraploid parents. CONCLUSION: Overall, these findings imply that improved FCR resistance in SHWs compared with their tetraploid parents is probably related to higher levels of response on PAL-mediated lignin and SA biosynthesis pathways.

Transcriptomic analysis provides insight into the genetic regulation of shade avoidance in Aegilops tauschii.

BACKGROUND: Weeds are not only economically important but also fascinating models for studying the adaptation of species in human-mediated environments. Aegilops tauschii is the D-genome donor species of common wheat but is also a weed that influences wheat production. How shading stress caused by adjacent wheat plants affects Ae. tauschii growth is a fundamental scientific question but is also important in agriculture, such as for weed control and wheat breeding. RESULT: The present study indicated that shade avoidance is a strategy of Ae. tauschii in response to shading stress. Ae. tauschii plants exhibited growth increases in specific organs, such as stem and leaf elongation, to avoid shading. However, these changes were accompanied by sacrificing the growth of other parts of the plants, such as a reduction in tiller number. The two reverse phenotype responses seem to be formed by systemically regulating the expression of different genes. Fifty-six genes involved in the regulation of cell division and cell expansion were found to be downregulated, and one key upstream negative regulator (RPK2) of cell division was upregulated under shading stress. On the other hand, the upregulated genes under shading stress were mainly enriched in protein serine/threonine kinase activity and carbon metabolism, which are associated with cell enlargement, signal transduction and energy supply. The transcription factor WRKY72 may be important in regulating genes in response to shading stress, which can be used as a prior candidate gene for further study on the genetic regulation of shade avoidance. CONCLUSIONS: This study sheds new light on the gene expression changes and molecular processes involved in the response and avoidance of Ae. tauschii to shading stress, which may aid more effective development of shading stress avoidance or cultivars in wheat and other crops in the future.

Identification and fine-mapping of QYrAS286-2BL conferring adult-plant resistance to stripe rust in cultivated emmer wheat.

KEY MESSAGE: A novel major adult-plant stripe rust resistance QTL derived from cultivated emmer wheat was mapped to a 123.6-kb region on wheat chromosome 2BL. Stripe rust, caused by the fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat. Identification of new sources of resistance and their utilization in breeding programs is the effectively control strategy. The objective of this study was to identify and genetically characterize the stripe rust resistance derived from the cultivated emmer accession AS286. A recombinant inbred line population, developed from a cross between the susceptible durum wheat line langdon and AS286, was genotyped using the Wheat55K single nucleotide polymorphism array and evaluated in field conditions with a mixture of the prevalent Chinese Pst races (CYR32, CYR33, CYR34, Zhong4, and HY46) and in growth chamber with race CYR34. Three QTLs conferring resistance were mapped on chromosomes 1BS, 2BL, and 5BL, respectively. The QYrAS286-1BS and QYrAS286-2BL were stable with major effects, explaining 12.91% to 18.82% and 11.31% to 31.43% of phenotypic variation, respectively. QYrAS286-5BL was only detected based on growth chamber seedling data. RILs harboring both QYrAS286-1BS and QYrAS286-2BL showed high levels of stripe rust resistance equal to the parent AS286. The QYrAS286-2BL was only detected at the adult-plant stage, which is different from previously named Yr genes and inherited as a single gene. It was further mapped to a 123.6-kb region using KASP markers derived from SNPs identified by bulked segregant RNA sequencing (BSR-Seq). The identified loci enrich our stripe rust resistance gene pool, and the flanking markers developed here could be useful in marker-assisted selection for incorporating QYrAS286-2BL into wheat cultivars.

Cytogenetic Characterization and Molecular Marker Development for a Wheat-T. boeoticum 4Ab (4B) Disomic Substitution Line with Stripe Rust Resistance.

Triticum boeoticum (2n = 2x = 14, AbAb) is an important relative of wheat. This species tolerates many different types of environmental stresses, including drought, salt, and pathogenic infection, and is lower in dietary fiber and higher in antioxidants, protein (15 to 18%), lipids, and trace elements than common wheat. However, the gene transfer rate from this species to common wheat is low, and few species-specific molecular markers are available. In this study, the wheat-T. boeoticum substitution line Z1889, derived from a cross between the common wheat cultivar Crocus and T. boeoticum line G52, was identified using multicolor fluorescence in situ hybridization, multicolor genomic in situ hybridization, and a 55K single-nucleotide polymorphism array. Z1889 was revealed to be a 4Ab (4B) substitution line with a high degree of resistance to stripe rust pathogen strains prevalent in China. In addition, 22 4Ab chromosome-specific molecular markers and 11 T. boeoticum genome-specific molecular markers were developed from 1,145 4Ab chromosome-specific fragments by comparing the sequences generated by specific-length amplified fragment sequencing, with an efficiency of up to 55.0%. Furthermore, the specificity of these markers was verified in four species containing the Ab genome. These markers not only can be used for the detection of the 4Ab chromosome but also provide a basis for molecular marker-assisted, selection-based breeding in wheat.

Pyramiding of Adult-Plant Resistance Genes Enhances All-Stage Resistance to Wheat Stripe Rust.

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most destructive diseases in wheat production. Pyramiding of adult-plant resistance (APR) genes is a promising strategy to increase durability of resistance. The stripe rust resistance (R) genes Yr18, Yr28, and Yr36 encode different protein families which confer partial resistance to a broad array of P. striiformis f. sp. tritici races. Here, we developed BC3F5 wheat lines representing all possible combinations of Yr18, Yr28, and Yr36 in a genetic background of the highly P. striiformis f. sp. tritici-susceptible wheat line SY95-71 that is widely used in stripe rust analysis. These lines enabled us to accurately evaluate these genes singly and in combination in a common genetic background. The adult plant resistance experiments were analyzed in the field, where stripe rust epidemics occurred frequently. The field results indicated that these partial R genes act additively in enhancing the levels of resistance, and a minimum of two-gene combinations can generate adequate stripe rust resistance. The Yr28 + Yr36 and Yr18 + Yr28 + Yr36 combinations also showed adequate resistance at the seedling stage, implying that APR gene pyramiding can achieve all-stage resistance. Meanwhile, the three genes were simultaneously introduced into elite wheat lines through gene-based marker selection. Elite lines exhibited strong all-stage resistance to stripe rust. This work provides valuable insights and resources for developing durable P. striiformis f. sp. tritici-resistant varieties and for elucidating the regulation mechanism of partial R gene pyramiding.

Identification of the Solid Stem Suppressor Gene Su-TdDof in Synthetic Hexaploid Wheat Syn-SAU-117.

Lodging is one of the most important factors affecting the high and stable yield of wheat worldwide. Solid-stemmed wheat has higher stem strength and lodging resistance than hollow-stemmed wheat does. There are many solid-stemmed varieties, landraces, and old varieties of durum wheat. However, the transfer of solid stem genes from durum wheat is suppressed by a suppressor gene located on chromosome 3D in common wheat, and only hollow-stemmed lines have been created. However, synthetic hexaploid wheat can serve as a bridge for transferring solid stem genes from tetraploid wheat to common wheat. In this study, the F1, F2, and F2:3 generations of a cross between solid-stemmed Syn-SAU-119 and semisolid-stemmed Syn-SAU-117 were developed. A single dominant gene, which was tentatively designated Su-TdDof and suppresses stem solidity, was identified in synthetic hexaploid wheat Syn-SAU-117 by using genetic analysis. By using bulked segregant RNA-seq (BSR-seq) analysis, Su-TdDof was mapped to chromosome 7DS and flanked by markers KASP-669 and KASP-1055 within a 4.53 cM genetic interval corresponding to 3.86 Mb and 2.29 Mb physical regions in the Chinese Spring (IWGSC RefSeq v1.1) and Ae. tauschii (AL8/78 v4.0) genomes, respectively, in which three genes related to solid stem development were annotated. Su-TdDof differed from a previously reported solid stem suppressor gene based on its origin and position. Su-TdDof would provide a valuable example for research on the suppression phenomenon. The flanking markers developed in this study might be useful for screening Ae. tauschii accessions with no suppressor gene (Su-TdDof) to develop more synthetic hexaploid wheat lines for the breeding of lodging resistance in wheat and further cloning the suppressor gene Su-TdDof.

Development and Characterization of Near-Isogenic Lines Derived from Synthetic Wheat Revealing the 2 kb Insertion in the PPD-D1 Gene Responsible for Heading Delay and Grain Number Improvement.

Spikelet number and grain number per spike are two crucial and correlated traits for grain yield in wheat. Photoperiod-1 (Ppd-1) is a key regulator of inflorescence architecture and spikelet formation in wheat. In this study, near-isogenic lines derived from the cross of a synthetic hexaploid wheat and commercial cultivars generated by double top-cross and two-phase selection were evaluated for the number of days to heading and other agronomic traits. The results showed that heading time segregation was conferred by a single incomplete dominant gene PPD-D1, and the 2 kb insertion in the promoter region was responsible for the delay in heading. Meanwhile, slightly delayed heading plants and later heading plants obviously have advantages in grain number and spikelet number of the main spike compared with early heading plants. Utilization of PPD-D1 photoperiod sensitivity phenotype as a potential means to increase wheat yield potential.

The PGS1 basic helix-loop-helix protein regulates Fl3 to impact seed growth and grain yield in cereals.

Plant transcription factors (TFs), such as basic helix-loop-helix (bHLH) and AT-rich zinc-binding proteins (PLATZ), play critical roles in regulating the expression of developmental genes in cereals. We identified the bHLH protein TaPGS1 (T. aestivum Positive Regulator of Grain Size 1) specifically expressed in the seeds at 5-20 days post-anthesis in wheat. TaPGS1 was ectopically overexpressed (OE) in wheat and rice, leading to increased grain weight (up to 13.81% in wheat and 18.55% in rice lines) and grain size. Carbohydrate and total protein levels also increased. Scanning electron microscopy results indicated that the starch granules in the endosperm of TaPGS1 OE wheat and rice lines were smaller and tightly embedded in a proteinaceous matrix. Furthermore, TaPGS1 was bound directly to the E-box motif at the promoter of the PLATZ TF genes TaFl3 and OsFl3 and positively regulated their expression in wheat and rice. In rice, the OsFl3 CRISPR/Cas9 knockout lines showed reduced average thousand-grain weight, grain width, and grain length in rice. Our results reveal that TaPGS1 functions as a valuable trait-associated gene for improving cereal grain yield.

Porous Copper-Loaded Zeolites for High-Efficiency Capture of Iodine from Spent Fuel Reprocessing Off-Gas.

Capturing volatile radionuclide iodine produced in the nuclear industry is a crucial environmental issue. In previous studies, the principal efficient adsorbent for iodine capture was silver-containing zeolite. As silver-containing zeolites are expensive, alternate copper-loaded porous zeolites, including CuCl loaded NaY reduced by H2 (denoted as H2CuY) and CO (denoted as COCuY), were studied for iodine adsorption at moderate temperatures. The current work also discusses the influence of copper valency on iodine adsorption. Due to the copper sites and nanosized pore structure, H2CuY and COCuY showed high iodine adsorption capacities of 450 and 219 mg/g, respectively. The iodine adsorption capacity of H2CuY was higher than that of silver-loaded zeolites. Moreover, H2CuY and COCuY adsorbed volatile iodine through a chemical mechanism involving the copper sites of different valencies, and the Cu0 was more effective in adsorbing iodine than Cu+. These copper-loaded zeolites with strong chemical interactions with iodine and high iodine adsorption capacities provided the possibility for iodine adsorption application in the nuclear industry.

Identification of a recessive gene YrZ15-1370 conferring adult plant resistance to stripe rust in wheat-Triticum boeoticum introgression line.

KEY MESSAGE: A novel recessive gene YrZ15-1370 derived from Triticum boeoticum confers adult-plant resistance to wheat stripe rust. Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most damaging diseases of wheat globally and resistance is the effectively control strategy. Triticum boeoticum Boiss (T. monococcum L. ssp. aegilopoides, 2n = 2x = 14, AbAb) accession G52 confers a high level of adult-plant resistance against a mixture of the Chinese prevalent Pst races. To transfer the resistance to common wheat, a cross was made between G52 and susceptible common wheat genotype Crocus. A highly resistant wheat-T. boeoticum introgression line Z15-1370 (F5 generation) with 42 chromosomes was selected cytologically and by testing with Pst races. F1, F2, and F2:3 generations of the cross between Z15-1370 and stripe rust susceptible common wheat Mingxian169 were developed. Genetic analysis revealed that the resistance in Z15-1370 was controlled by a single recessive gene, tentatively designated YrZ15-1370. Using the bulked segregant RNA-Seq (BSR-Seq) analysis, YrZ15-1370 was mapped to chromosome 6AL and flanked by markers KASP1370-3 and KASP-1370-5 within a 4.3 cM genetic interval corresponding to 1.8 Mb physical region in the Chinese Spring genome, in which a number of disease resistance-related genes were annotated. YrZ15-1370 differed from previously Yr genes identified on chromosome 6A based on its position and/or origin. The YrZ15-1370 would be a valuable resource for wheat resistance improvement and the flanking markers developed here could be useful tools for marker-assisted selection (MAS) in breeding and further cloning the gene.

Relationship between L-lactate dehydrogenase and multidrug resistance in Staphylococcus xylosus.

Staphylococcus xylosus is a gram-positive bacterium that has attracted much attention due to its increasing clinical appearance, frequently associated with serious multidrug resistance cases. L-lactate dehydrogenase (LDH) has been related to drug resistance in several bacterial species. However, the mechanism of multidrug resistance in S. xylosus remains unclear as well as the involvement of LDH in such resistance. To explore the relationship between multidrug resistance and LDH in S. xylosus, we used tylosin-resistant S. xylosus as the parent strain to construct ldh knockout and complemented strains. Then, we tested their resistance to macrolides, lincosamides, tetracyclines, and aminoglycosides. In addition, the enzyme activity, metabolite content, and transcriptional level of key genes involved in the TCA cycle and thioredoxin system were determined to clarify the mechanism of resistance. We observed that the resistance to multiple antibiotics increased significantly after ldh knockout, especially that to lincomycin, whereas antibiotic sensitivity was partially restored in the complemented strain. The levels of pyruvate, nicotinamide adenine dinucleotide, and reactive oxygen species decreased significantly upon ldh knockout, and the activity of isocitrate dehydrogenase and malate dehydrogenase decreased. These results indicate that the lack of LDH promotes multidrug resistance in S. xylosus by inhibiting the TCA cycle and regulating the thioredoxin system.

Differences between diploid donors are the main contributing factor for subgenome asymmetry measured in either gene ratio or relative diversity in allopolyploids.

Subgenome asymmetry (SA) has routinely been attributed to different responses between the subgenomes of a polyploid to various stimuli during evolution. Here, we compared subgenome differences in gene ratio and relative diversity between artificial and natural genotypes of several allopolyploid species. Surprisingly, consistent differences were not detected between these two types of polyploid genotypes, although they differ in times exposed to evolutionary selection. The estimated ratio of shared genes between a subgenome and its diploid donor was invariably higher for the artificial allopolyploid genotypes than those for the natural genotypes, which is expected as it is now well-known that many genes in a species are not shared among all individuals. As the exact diploid parent for a given subgenome is unknown, the estimated ratios of shared genes for the natural genotypes would also include difference among individual genotypes of the diploid donor species. Further, we detected the presence of SA in genotypes before the completion of the polyploidization events as well as in those which were not formed via polyploidization. These results indicate that SA may, to a large degree, reflect differences between its diploid donors or that changes occurred during polyploid evolution are defined by their donor genomes.

A transcriptomic view of the ability of nascent hexaploid wheat to tolerate aneuploidy.

BACKGROUND: In contrast to most animal species, polyploid plant species are quite tolerant of aneuploidy. Here, the global transcriptome of four aneuploid derivatives of a synthetic hexaploid wheat line was acquired, with the goal of characterizing the relationship between gene copy number and transcript abundance. RESULTS: For most of the genes mapped to the chromosome involved in aneuploidy, the abundance of transcripts reflected the gene copy number. Aneuploidy had a greater effect on the strength of transcription of genes mapped to the chromosome present in a noneuploid dose than on that of genes mapped elsewhere in the genome. Overall, changing the copy number of one member of a homeologous set had little effect on the abundance of transcripts generated from the set of homeologs as a whole, consistent with the tolerance of aneuploidy exhibited by allopolyploids, whether in the form of a chromosomal deficit (monosomy) or chromosomal excess (trisomy). CONCLUSIONS: Our findings shed new light on the genetic regulation of homeoallele transcription and contribute to a deeper understanding of allopolyploid genome evolution, with implications for the breeding of polyploid crops.

Genetic mapping of a major QTL promoting homoeologous chromosome pairing in a wheat landrace.

KEY MESSAGE: Common wheat landrace Kaixian-luohanmai carries a gene(s) that promotes homoeologous chromosome pairing. A major QTL responsible for this effect was mapped to chromosome arm 3AL. Polyhaploid hybrids of a Chinese common wheat landrace Kaixian-luohanmai (KL) and related species show increased levels of chromosome pairing. Over 90% of that pairing is between homoeologous arms of wheat chromosomes, with a very strong preference for pairing between homoeologs from genomes A and D. Wheat-rye pairing was also observed at low frequency. Two mapping populations were created from the hybrids of KL with two wheat genotypes top crossed to rye. Mean chiasmata numbers per plant were used as phenotypic data. Wheat 660 K and 15 K SNP arrays, DArT markers and SSR markers were used for genotyping of the top-cross ABDR hybrids. One major QTL, named QPh.sicau-3A, for increased homoeologous pairing was detected on chromosome arm 3AL, and it was responsible for ca. 16% of the total variation. This QTL was located in the interval 696-725 Mb in the Chinese Spring reference genome. SNP markers closely linked with QPh.sicau-3A were converted to KASP markers and validated for marker-assisted selection.

A breeding strategy targeting the secondary gene pool of bread wheat: introgression from a synthetic hexaploid wheat.

KEY MESSAGE: Introgressing one-eighth of synthetic hexaploid wheat genome through a double top-cross plus a two-phase selection is an effective strategy to develop high-yielding wheat varieties. The continued expansion of the world population and the likely onset of climate change combine to form a major crop breeding challenge. Genetic advances in most crop species to date have largely relied on recombination and reassortment within a relatively narrow gene pool. Here, we demonstrate an efficient wheat breeding strategy for improving yield potentials by introgression of multiple genomic regions of de novo synthesized wheat. The method relies on an initial double top-cross (DTC), in which one parent is synthetic hexaploid wheat (SHW), followed by a two-phase selection procedure. A genotypic analysis of three varieties (Shumai 580, Shumai 969 and Shumai 830) released from this program showed that each harbors a unique set of genomic regions inherited from the SHW parent. The first two varieties were generated from very small populations, whereas the third used a more conventional scale of selection since one of bread wheat parents was a pre-breeding material. The three varieties had remarkably enhanced yield potential compared to those developed by conventional breeding. A widely accepted consensus among crop breeders holds that introducing unadapted germplasm, such as landraces, as parents into a breeding program is a risky proposition, since the size of the breeding population required to overcome linkage drag becomes too daunting. However, the success of the proposed DTC strategy has demonstrated that novel variation harbored by SHWs can be accessed in a straightforward, effective manner. The strategy is in principle generalizable to any allopolyploid crop species where the identity of the progenitor species is known.

The antibacterial mechanism of oridonin against methicillin-resistant Staphylococcus aureus (MRSA).

Context: Methicillin-resistant Staphylococcus aureus (MRSA) is a very harmful bacterium. Oridonin, a component in Rabdosia rubescens (Hemsl.) Hara (Lamiaceae), is widely used against bacterial infections in China. Objective: We evaluated oridonin effects on MRSA cell membrane and wall, protein metabolism, lactate dehydrogenase (LDH), DNA and microscopic structure. Materials and methods: Broth microdilution and flat colony counting methods were used to measure oridonin minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against USA300 strain. Electrical conductivity and DNA exosmosis were analysed to study oridonin effects (128 µg/mL) on cell membrane and wall for 0, 1, 2, 4 and 6 h. Sodium dodecyl sulphate polyacrylamide gel electrophoresis was used to detect effects on soluble protein synthesis after 6, 10 and 16 h. LDH activity was examined with an enzyme-linked immunosorbent assay. Effects of oridonin on USA300 DNA were investigated with DAPI staining. Morphological changes in MRSA following oridonin treatment were determined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results: Oridonin MIC and MBC values against USA300 were 64 and 512 µg/mL, respectively. The conductivity and DNA exosmosis level of oridonin-treated USA300 improved by 3.20±0.84% and increased by 58.63 ± 1.78 µg/mL, respectively. LDH and soluble protein levels decreased by 30.85±7.69% and 27.51 ± 1.39%, respectively. A decrease in fluorescence intensity was reported with time. Oridonin affected the morphology of USA300. Conclusions: Oridonin antibacterial mechanism was related to changes in cell membrane and cell wall permeability, disturbance in protein and DNA metabolism, and influence on bacterial morphology. Thus, oridonin may help in treating MRSA infection.

Fluorescence in situ hybridization karyotyping reveals the presence of two distinct genomes in the taxon Aegilops tauschii.

BACKGROUND: Aegilops tauschii is the donor of the bread wheat D genome. Based on spike morphology, the taxon has conventionally been subdivided into ssp. tauschii and ssp. strangulata. The present study was intended to address the poor match between this whole plant morphology-based subdivision and genetic relationships inferred from genotyping by fluorescence in situ hybridization karyotyping a set of 31 Ae. tauschii accessions. RESULTS: The distribution of sites hybridizing to the two probes oligo-pTa-535 and (CTT)10 split the Ae. tauschii accessions into two clades, designated Dt and Ds, which corresponded perfectly with a previously assembled phylogeny based on marker genotype. The Dt cluster was populated exclusively by ssp. tauschii accessions, while the Ds cluster harbored both ssp. strangulata and morphologically intermediate accessions. As a result, it is proposed that Ae. tauschii ssp. tauschii is restricted to carriers of the Dt karyotype: their spikelets are regularly spaced along the rachis, at least in the central portion of their spike. Accessions classified as Ae. tauschii ssp. strangulata carry the Ds karyotype; their spikelets are irregularly spaced. Based on this criterion, forms formerly classified as ssp. tauschii var. meyeri have been re-designated ssp. strangulata var. meyeri. CONCLUSIONS: According to the reworking of the taxon, the bread wheat D genome was most probably donated by ssp. strangulata var. meyeri. Chromosomal differentiation reveals intra-species taxon of Ae. tauschii. Ae. tauschii ssp. tauschii has more distant relationship with breed wheat than ssp. strangulata and can be used for breeding improving effectively.

The abundance of homoeologue transcripts is disrupted by hybridization and is partially restored by genome doubling in synthetic hexaploid wheat.

BACKGROUND: The formation of an allopolyploid is a two step process, comprising an initial wide hybridization event, which is later followed by a whole genome doubling. Both processes can affect the transcription of homoeologues. Here, RNA-Seq was used to obtain the genome-wide leaf transcriptome of two independent Triticum turgidum × Aegilops tauschii allotriploids (F1), along with their spontaneous allohexaploids (S1) and their parental lines. The resulting sequence data were then used to characterize variation in homoeologue transcript abundance. RESULTS: The hybridization event strongly down-regulated D-subgenome homoeologues, but this effect was in many cases reversed by whole genome doubling. The suppression of D-subgenome homoeologue transcription resulted in a marked frequency of parental transcription level dominance, especially with respect to genes encoding proteins involved in photosynthesis. Singletons (genes where no homoeologues were present) were frequently transcribed at both the allotriploid and allohexaploid plants. CONCLUSIONS: The implication is that whole genome doubling helps to overcome the phenotypic weakness of the allotriploid, restoring a more favourable gene dosage in genes experiencing transcription level dominance in hexaploid wheat.