Meiotic recombination is a critical process for plant breeding, as it creates novel allele combinations that can be exploited for crop improvement. In wheat, a complex allohexaploid that has a diploid-like behaviour, meiotic recombination between homoeologous or alien chromosomes is suppressed through the action of several loci. Here, we report positional cloning of Pairing homoeologous 2 (Ph2) and functional validation of the wheat DNA mismatch repair protein MSH7-3D as a key inhibitor of homoeologous recombination, thus solving a half-century-old question. Similar to ph2 mutant phenotype, we show that mutating MSH7-3D induces a substantial increase in homoeologous recombination (up to 5.5 fold) in wheat-wild relative hybrids, which is also associated with a reduction in homologous recombination. These data reveal a role for MSH7-3D in meiotic stabilisation of allopolyploidy and provides an opportunity to improve wheat's genetic diversity through alien gene introgression, a major bottleneck facing crop improvement.
- MeSH
- alely MeSH
- chiméra MeSH
- chromozomy rostlin chemie MeSH
- DNA rostlinná genetika metabolismus MeSH
- fyzikální mapování chromozomů MeSH
- homologní rekombinace * MeSH
- meióza MeSH
- mutace MeSH
- oprava chybného párování bází DNA MeSH
- ploidie MeSH
- pšenice genetika metabolismus MeSH
- regulace genové exprese u rostlin * MeSH
- rostlinné proteiny genetika metabolismus MeSH
- šlechtění rostlin metody MeSH
- žito genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Unraveling and exploiting mechanisms of disease resistance in cereal crops is currently limited by their large repeat-rich genomes and the lack of genetic recombination or cultivar (cv)-specific sequence information. We cloned the first leaf rust resistance gene Rph1 (Rph1a) from cultivated barley (Hordeum vulgare) using "MutChromSeq," a recently developed molecular genomics tool for the rapid cloning of genes in plants. Marker-trait association in the CI 9214/Stirling doubled haploid population mapped Rph1 to the short arm of chromosome 2H in a physical region of 1.3 megabases relative to the barley cv Morex reference assembly. A sodium azide mutant population in cv Sudan was generated and 10 mutants were confirmed by progeny-testing. Flow-sorted 2H chromosomes from Sudan (wild type) and six of the mutants were sequenced and compared to identify candidate genes for the Rph1 locus. MutChromSeq identified a single gene candidate encoding a coiled-coil nucleotide binding site Leucine-rich repeat (NLR) receptor protein that was altered in three different mutants. Further Sanger sequencing confirmed all three mutations and identified an additional two independent mutations within the same candidate gene. Phylogenetic analysis determined that Rph1 clustered separately from all previously cloned NLRs from the Triticeae and displayed highest sequence similarity (89%) with a homolog of the Arabidopsis (Arabidopsis thaliana) disease resistance protein 1 protein in Triticum urartu In this study we determined the molecular basis for Rph1-mediated resistance in cultivated barley enabling varietal improvement through diagnostic marker design, gene editing, and gene stacking technologies.
Bread wheat (Triticum aestivum L.) is a staple food for a significant part of the world's population. The growing demand on its production can be satisfied by improving yield and resistance to biotic and abiotic stress. Knowledge of the genome sequence would aid in discovering genes and QTLs underlying these traits and provide a basis for genomics-assisted breeding. Physical maps and BAC clones associated with them have been valuable resources from which to generate a reference genome of bread wheat and to assist map-based gene cloning. As a part of a joint effort coordinated by the International Wheat Genome Sequencing Consortium, we have constructed a BAC-based physical map of bread wheat chromosome arm 7DS consisting of 895 contigs and covering 94% of its estimated length. By anchoring BAC contigs to one radiation hybrid map and three high resolution genetic maps, we assigned 73% of the assembly to a distinct genomic position. This map integration, interconnecting a total of 1713 markers with ordered and sequenced BAC clones from a minimal tiling path, provides a tool to speed up gene cloning in wheat. The process of physical map assembly included the integration of the 7DS physical map with a whole-genome physical map of Aegilops tauschii and a 7DS Bionano genome map, which together enabled efficient scaffolding of physical-map contigs, even in the non-recombining region of the genetic centromere. Moreover, this approach facilitated a comparison of bread wheat and its ancestor at BAC-contig level and revealed a reconstructed region in the 7DS pericentromere.
- MeSH
- Aegilops genetika MeSH
- centromera genetika MeSH
- chromozomy rostlin genetika MeSH
- fyzikální mapování chromozomů metody MeSH
- genom rostlinný MeSH
- hybridizace genetická MeSH
- klonování DNA MeSH
- pšenice genetika MeSH
- rostlinné geny MeSH
- šlechtění rostlin MeSH
- umělé bakteriální chromozomy genetika MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
Any project seeking to deliver a plant or animal reference genome sequence must address the question as to the completeness of the assembly. Given the complexity introduced particularly by the presence of sequence redundancy, a problem which is especially acute in polyploid genomes, this question is not an easy one to answer. One approach is to use the sequence data, along with the appropriate computational tools, the other is to compare the estimate of genome size with an experimentally measured mass of nuclear DNA. The latter requires a reference standard in order to provide a robust relationship between the two independent measurements of genome size. Here, the proposal is to choose the human male leucocyte genome for this standard: its 1C DNA amount (the amount of DNA contained within unreplicated haploid chromosome set) of 3.50 pg is equivalent to a genome length of 3.423 Gbp, a size which is just 5% longer than predicted by the most current human genome assembly. Adopting this standard, this paper assesses the completeness of the reference genome assemblies of the leading cereal crops species wheat, barley and rye.
- MeSH
- délka genomu * MeSH
- genom lidský MeSH
- genom rostlinný * MeSH
- lidé MeSH
- pšenice genetika MeSH
- referenční standardy MeSH
- sekvenční analýza DNA * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Despite a long history, the production of useful alien introgression lines in wheat remains difficult mainly due to linkage drag and incomplete genetic compensation. In addition, little is known about the molecular mechanisms underlying the impact of foreign chromatin on plant phenotype. Here, a comparison of the transcriptomes of barley, wheat and a wheat-barley 7HL addition line allowed the transcriptional impact both on 7HL genes of a non-native genetic background and on the wheat gene complement as a result of the presence of 7HL to be assessed. Some 42% (389/923) of the 7HL genes assayed were differentially transcribed, which was the case for only 3% (960/35 301) of the wheat gene complement. The absence of any transcript in the addition line of a suite of chromosome 7A genes implied the presence of a 36 Mbp deletion at the distal end of the 7AL arm; this deletion was found to be in common across the full set of Chinese Spring/Betzes barley addition lines. The remaining differentially transcribed wheat genes were distributed across the whole genome. The up-regulated barley genes were mostly located in the proximal part of the 7HL arm, while the down-regulated ones were concentrated in the distal part; as a result, genes encoding basal cellular functions tended to be transcribed, while those encoding specific functions were suppressed. An insight has been gained into gene transcription in an alien introgression line, thereby providing a basis for understanding the interactions between wheat and exotic genes in introgression materials.
The movement of nuclear DNA from one vascular plant species to another in the absence of fertilization is thought to be rare. Here, nonnative rRNA gene [ribosomal DNA (rDNA)] copies were identified in a set of 16 diploid barley (Hordeum) species; their origin was traceable via their internal transcribed spacer (ITS) sequence to five distinct Panicoideae genera, a lineage that split from the Pooideae about 60 Mya. Phylogenetic, cytogenetic, and genomic analyses implied that the nonnative sequences were acquired between 1 and 5 Mya after a series of multiple events, with the result that some current Hordeum sp. individuals harbor up to five different panicoid rDNA units in addition to the native Hordeum rDNA copies. There was no evidence that any of the nonnative rDNA units were transcribed; some showed indications of having been silenced via pseudogenization. A single copy of a Panicum sp. rDNA unit present in H. bogdanii had been interrupted by a native transposable element and was surrounded by about 70 kbp of mostly noncoding sequence of panicoid origin. The data suggest that horizontal gene transfer between vascular plants is not a rare event, that it is not necessarily restricted to one or a few genes only, and that it can be selectively neutral.
- MeSH
- buněčné jádro genetika MeSH
- diploidie MeSH
- DNA rostlinná chemie genetika MeSH
- fylogeneze * MeSH
- ječmen (rod) klasifikace genetika MeSH
- lipnicovité klasifikace genetika MeSH
- mezerníky ribozomální DNA chemie genetika MeSH
- molekulární evoluce MeSH
- přenos genů horizontální * MeSH
- ribozomální DNA chemie genetika MeSH
- rostlinné geny genetika MeSH
- sekvenční analýza DNA MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Fluorescence in situ hybridization (FISH) is a widely used method to localize DNA sequences on mitotic and meiotic chromosomes and interphase nuclei. It was developed in early 1980s and since then it has contributed to numerous studies and important discoveries. Over the decades, the protocol was modified for ease of use, allowing for localizing multiple probes simultaneously and increasing its sensitivity and specificity. Despite the continuous improvements, the ability to detect short single-copy sequences of only a few kilobases or less, such as genes, remains limited. Here, we provide a detailed protocol for detection of short, single- or low-copy sequences on plant mitotic metaphase chromosomes.
Photosynthesis in plants and algae relies on the coordinated function of photosystems (PS) I and II. Their efficiency is augmented by finely-tuned light-harvesting proteins (Lhcs) connected to them. The most recent Lhcs (in evolutionary terms), Lhcb6 and Lhcb3, evolved during the transition of plants from water to land and have so far been considered to be an essential characteristic of land plants. We used single particle electron microscopy and sequence analysis to study architecture and composition of PSII supercomplex from Norway spruce and related species. We have found that there are major land plant families that lack functional lhcb6 and lhcb3 genes, which notably changes the organization of PSII supercomplexes. The Lhcb6 and Lhcb3 proteins have been lost in the gymnosperm genera Picea and Pinus (family Pinaceae) and Gnetum (Gnetales). We also revealed that the absence of these proteins in Norway spruce modifies the PSII supercomplex in such a way that it resembles its counterpart in the alga Chlamydomonas reinhardtii, an evolutionarily older organism. Our results break a deep-rooted concept of Lhcb6 and Lhcb3 proteins being the essential characteristic of land plants, and beg the question of what the evolutionary benefit of their loss could be.
- MeSH
- biologická evoluce * MeSH
- fotosystém II - proteinový komplex metabolismus MeSH
- fylogeneze MeSH
- podjednotky proteinů chemie metabolismus MeSH
- rostlinné geny MeSH
- rostlinné proteiny metabolismus MeSH
- sekvenční homologie aminokyselin MeSH
- světlosběrné proteinové komplexy metabolismus ultrastruktura MeSH
- vyšší rostliny metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Aldehyde dehydrogenases (ALDHs) are responsible for oxidation of biogenic aldehyde intermediates as well as for cell detoxification of aldehydes generated during lipid peroxidation. So far, 13 ALDH families have been described in plants. In the present study, we provide a detailed biochemical characterization of plant ALDH2 and ALDH7 families by analysing maize and pea ALDH7 (ZmALDH7 and PsALDH7) and four maize cytosolic ALDH(cALDH)2 isoforms RF2C, RF2D, RF2E and RF2F [the first maize ALDH2 was discovered as a fertility restorer (RF2A)]. We report the crystal structures of ZmALDH7, RF2C and RF2F at high resolution. The ZmALDH7 structure shows that the three conserved residues Glu(120), Arg(300) and Thr(302) in the ALDH7 family are located in the substrate-binding site and are specific to this family. Our kinetic analysis demonstrates that α-aminoadipic semialdehyde, a lysine catabolism intermediate, is the preferred substrate for plant ALDH7. In contrast, aromatic aldehydes including benzaldehyde, anisaldehyde, cinnamaldehyde, coniferaldehyde and sinapaldehyde are the best substrates for cALDH2. In line with these results, the crystal structures of RF2C and RF2F reveal that their substrate-binding sites are similar and are formed by an aromatic cluster mainly composed of phenylalanine residues and several nonpolar residues. Gene expression studies indicate that the RF2C gene, which is strongly expressed in all organs, appears essential, suggesting that the crucial role of the enzyme would certainly be linked to the cell wall formation using aldehydes from phenylpropanoid pathway as substrates. Finally, plant ALDH7 may significantly contribute to osmoprotection because it oxidizes several aminoaldehydes leading to products known as osmolytes.
- MeSH
- aldehyddehydrogenasa chemie genetika metabolismus MeSH
- fylogeneze MeSH
- hrách setý enzymologie genetika MeSH
- izoenzymy chemie genetika metabolismus MeSH
- katalytická doména genetika MeSH
- kinetika MeSH
- krystalografie rentgenová MeSH
- kukuřice setá enzymologie genetika MeSH
- modely genetické MeSH
- molekulární modely MeSH
- molekulární sekvence - údaje MeSH
- NAD metabolismus MeSH
- rostlinné proteiny chemie genetika metabolismus MeSH
- rostliny enzymologie genetika MeSH
- sekvence aminokyselin MeSH
- stanovení celkové genové exprese MeSH
- substrátová specifita MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
