RESUMEN
KEY MESSAGE: The dwarfing allele Rht14 of durum wheat associates with greater stigma length, an important trait for hybrid breeding, whilst major dwarfing alleles Rht-B1b and Rht-D1b showed little to no effect. Although much understudied in wheat, the stigma is a crucial component for attaining grain set, the fundamental basis for yield, particularly in hybrid production systems where successful grain set relies on wind-driven pollen dispersal by the male parent and effective pollen capture by the female parent. Females with long stigma that exsert early are thought to be advantageous. Using glasshouse-grown lines, we examined variation in Total Stigma Length (TSL) across diverse panels comprising 27 durum and 116 bread wheat genotypes. Contrasting genotypes were selected for population development and genetic analysis. Quantitative trait loci (QTL) analysis was performed on a durum F2 population and a bread wheat recombinant inbred line (RIL) population. Contrasting with studies of anther length, we found no large effect on TSL of the GA-insensitive semi-dwarfing genes Rht-B1 and Rht-D1 in either durum or bread wheat. However, in durum cultivar Italo, we identified a region on chromosome 6A which is robustly associated with larger TSL and contains the Rht14 allele for reduced plant height, a trait that is favourable for female line development in hybrid systems. This dual effect locus explained 25.2 and 19.2% of TSL phenotypic variation in experiments across two growing seasons, with preliminary results suggesting this locus may increase TSL when transferred to bread wheat. In a bread wheat, RIL population minor QTL on 1A and 2A was indicated, but the strongest association was with Ppd-B1. Methods developed here, and the identification of a TSL-enhancing locus provides advances and further opportunities in the study of wheat stigma.
Asunto(s)
Alelos , Flores , Ligamiento Genético , Genotipo , Fenotipo , Sitios de Carácter Cuantitativo , Triticum , Triticum/genética , Triticum/crecimiento & desarrollo , Flores/genética , Flores/crecimiento & desarrollo , Mapeo Cromosómico , Genes de Plantas , Fitomejoramiento , PanRESUMEN
Correct floral development is the result of a sophisticated balance of molecular cues. Floral mutants provide insight into the main genetic determinants that integrate these cues, as well as providing opportunities to assess functional variation across species. In this study, we characterize the barley (Hordeum vulgare) multiovary mutants mov2.g and mov1, and propose causative gene sequences: a C2H2 zinc-finger gene HvSL1 and a B-class gene HvMADS16, respectively. In the absence of HvSL1, florets lack stamens but exhibit functional supernumerary carpels, resulting in multiple grains per floret. Deletion of HvMADS16 in mov1 causes homeotic conversion of lodicules and stamens into bract-like organs and carpels that contain non-functional ovules. Based on developmental, genetic, and molecular data, we propose a model by which stamen specification in barley is defined by HvSL1 acting upstream of HvMADS16. The present work identifies strong conservation of stamen formation pathways with other cereals, but also reveals intriguing species-specific differences. The findings lay the foundation for a better understanding of floral architecture in Triticeae, a key target for crop improvement.
Asunto(s)
Hordeum , Animales , Hordeum/genética , Hordeum/metabolismo , Ovario/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Flores , Poaceae/metabolismo , Regulación de la Expresión Génica de las Plantas , Proteínas de Dominio MADS/genéticaRESUMEN
Transition to the reproductive phase, inflorescence formation and flower development are crucial elements that ensure maximum reproductive success in a plant's life cycle. To understand the regulatory mechanisms underlying correct flower development in barley (Hordeum vulgare), we characterized the multiovary 5 (mov5.o) mutant. This mutant develops abnormal flowers that exhibit mosaic floral organs typified by multiple carpels at the total or partial expense of stamens. Genetic mapping positioned mov5 on the long arm of chromosome 2H, incorporating a region that encodes HvLFY, the barley orthologue of LEAFY from Arabidopsis. Sequencing revealed that, in mov5.o plants, HvLFY contains a single amino acid substitution in a highly conserved proline residue. CRISPR-mediated knockout of HvLFY replicated the mov5.o phenotype, suggesting that HvLFYmov5 represents a loss of function allele. In heterologous assays, the HvLFYmov5 polymorphism influenced protein-protein interactions and affinity for a putative binding site in the promoter of HvMADS58, a C-class MADS-box gene. Moreover, molecular analysis indicated that HvLFY interacts with HvUFO and regulates the expression of floral homeotic genes including HvMADS2, HvMADS4 and HvMADS16. Other distinct changes in expression differ from those reported in the rice LFY mutants apo2/rfl, suggesting that LFY function in the grasses is modulated in a species-specific manner. This pathway provides a key entry point for the study of LFY function and multiple ovary formation in barley, as well as cereal species in general.
Asunto(s)
Flores/crecimiento & desarrollo , Hordeum/fisiología , Proteínas de Plantas/genética , Sustitución de Aminoácidos , Proteínas de Arabidopsis/genética , Sitios de Unión , Mapeo Cromosómico , Cromosomas de las Plantas , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , ADN de Plantas/metabolismo , Flores/fisiología , Regulación de la Expresión Génica de las Plantas , Genes Homeobox , Hordeum/crecimiento & desarrollo , Inflorescencia/genética , Mutación , Proteínas de Plantas/metabolismo , Polimorfismo de Nucleótido Simple , Factores de Transcripción/genéticaRESUMEN
Functional divergence after gene duplication plays a central role in plant evolution. Among cereals, only Hordeum vulgare (barley), Triticum aestivum (wheat) and Secale cereale (rye) accumulate delphinidin-derived (blue) anthocyanins in the aleurone layer of grains, whereas Oryza sativa (rice), Zea mays (maize) and Sorghum bicolor (sorghum) do not. The underlying genetic basis for this natural occurrence remains elusive. Here, we mapped the barley Blx1 locus involved in blue aleurone to an approximately 1.13 Mb genetic interval on chromosome 4HL, thus identifying a trigenic cluster named MbHF35 (containing HvMYB4H, HvMYC4H and HvF35H). Sequence and expression data supported the role of these genes in conferring blue-coloured (blue aleurone) grains. Synteny analyses across monocot species showed that MbHF35 has only evolved within distinct Triticeae lineages, as a result of dispersed gene duplication. Phylogeny analyses revealed a shared evolution pattern for MbHF35 in Triticeae, suggesting that these genes have co-evolved together. We also identified a Pooideae-specific flavonoid 3',5'-hydroxylase (F3'5'H) lineage, termed here Mo_F35H2, which has a higher amino acid similarity with eudicot F3'5'Hs, demonstrating a scenario of convergent evolution. Indeed, selection tests identified 13 amino acid residues in Mo_F35H2 that underwent positive selection, possibly driven by protein thermostablility selection. Furthermore, through the interrogation of barley germplasm there is evidence that HvMYB4H and HvMYC4H have undergone human selection. Collectively, our study favours blue aleurone as a recently evolved trait resulting from environmental adaptation. Our findings provide an evolutionary explanation for the absence of blue anthocyanins in other cereals and highlight the importance of gene functional divergence for plant diversity and environmental adaptation.
Asunto(s)
Hordeum/genética , Proteínas de Plantas/genética , Adaptación Fisiológica/genética , Evolución Biológica , Mapeo Cromosómico , Color , Grano Comestible , Ambiente , Duplicación de Gen , Sitios Genéticos/genética , Hordeum/fisiología , Fenotipo , Filogenia , Proteínas de Plantas/metabolismoRESUMEN
Nuclear male-sterile mutants with non-conditional, recessive and strictly monogenic inheritance are useful for both hybrid and conventional breeding systems, and have long been a research focus for many crops. In allohexaploid wheat, however, genic redundancy results in rarity of such mutants, with the ethyl methanesulfonate-induced mutant ms5 among the few reported to date. Here, we identify TaMs5 as a glycosylphosphatidylinositol-anchored lipid transfer protein required for normal pollen exine development, and by transgenic complementation demonstrate that TaMs5-A restores fertility to ms5. We show ms5 locates to a centromere-proximal interval and has a sterility inheritance pattern modulated by TaMs5-D but not TaMs5-B. We describe two allelic forms of TaMs5-D, one of which is non-functional and confers mono-factorial inheritance of sterility. The second form is functional but shows incomplete dominance. Consistent with reduced functionality, transcript abundance in developing anthers was found to be lower for TaMs5-D than TaMs5-A. At the 3B homoeolocus, we found only non-functional alleles among 178 diverse hexaploid and tetraploid wheats that include landraces and Triticum dicoccoides. Apparent ubiquity of non-functional TaMs5-B alleles suggests loss-of-function arose early in wheat evolution and, therefore, at most knockout of two homoeoloci is required for sterility. This work provides genetic information, resources and tools required for successful implementation of ms5 sterility in breeding systems for bread and durum wheats.
Asunto(s)
Proteínas de Plantas/metabolismo , Triticum/metabolismo , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Infertilidad Vegetal/genética , Infertilidad Vegetal/fisiología , Proteínas de Plantas/genética , Polen/metabolismo , Polen/fisiología , Triticum/genética , Triticum/fisiologíaRESUMEN
BACKGROUND: The CRISPR-Cas9 system is a powerful and versatile tool for crop genome editing. However, achieving highly efficient and specific editing in polyploid species can be a challenge. The efficiency and specificity of the CRISPR-Cas9 system depends critically on the gRNA used. Here, we assessed the activities and specificities of seven gRNAs targeting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in hexaploid wheat protoplasts. EPSPS is the biological target of the widely used herbicide glyphosate. RESULTS: The seven gRNAs differed substantially in their on-target activities, with mean indel frequencies ranging from 0% to approximately 20%. There was no obvious correlation between experimentally determined and in silico predicted on-target gRNA activity. The presence of a single mismatch within the seed region of the guide sequence greatly reduced but did not abolish gRNA activity, whereas the presence of an additional mismatch, or the absence of a PAM, all but abolished gRNA activity. Large insertions (≥20 bp) of DNA vector-derived sequence were detected at frequencies up to 8.5% of total indels. One of the gRNAs exhibited several properties that make it potentially suitable for the development of non-transgenic glyphosate resistant wheat. CONCLUSIONS: We have established a rapid and reliable method for gRNA validation in hexaploid wheat protoplasts. The method can be used to identify gRNAs that have favourable properties. Our approach is particularly suited to polyploid species, but should be applicable to any plant species amenable to protoplast transformation.
Asunto(s)
Sistemas CRISPR-Cas/genética , Edición Génica/métodos , Genoma de Planta/genética , ARN Guía de Kinetoplastida/genética , Triticum/genética , Protoplastos/metabolismoRESUMEN
The development and adoption of hybrid seed technology have led to dramatic increases in agricultural productivity. However, it has been a challenge to develop a commercially viable platform for the production of hybrid wheat (Triticum aestivum) seed due to wheat's strong inbreeding habit. Recently, a novel platform for commercial hybrid seed production was described. This hybridization platform utilizes nuclear male sterility to force outcrossing and has been applied to maize and rice. With the recent molecular identification of the wheat male fertility gene Ms1, it is now possible to extend the use of this novel hybridization platform to wheat. In this report, we used the CRISPR/Cas9 system to generate heritable, targeted mutations in Ms1. The introduction of biallelic frameshift mutations into Ms1 resulted in complete male sterility in wheat cultivars Fielder and Gladius, and several of the selected male-sterile lines were potentially non-transgenic. Our study demonstrates the utility of the CRISPR/Cas9 system for the rapid generation of male sterility in commercial wheat cultivars. This represents an important step towards capturing heterosis to improve wheat yields, through the production and use of hybrid seed on an industrial scale.
Asunto(s)
Sistemas CRISPR-Cas , Infertilidad Vegetal , Semillas , Triticum/genética , Mutación del Sistema de Lectura , Técnicas de Inactivación de Genes , Genes de Plantas , PoliploidíaRESUMEN
KEY MESSAGE: Elite wheat pollinators are critical for successful hybrid breeding. We identified Rht-B1 and Ppd-D1 loci affecting multiple pollinator traits and therefore represent major targets for improving hybrid seed production. Hybrid breeding has a great potential to significantly boost wheat yields. Ideal male pollinators would be taller in stature, contain many spikelets well-spaced along the spike and exhibit high extrusion of large anthers. Most importantly, flowering time would match with that of the female parent. Available genetic resources for developing an elite wheat pollinator are limited, and the genetic basis for many of these traits is largely unknown. Here, we report on the genetic analysis of pollinator traits using biparental mapping populations. We identified two anther extrusion QTLs of medium effect, one on chromosome 1BL and the other on 4BS coinciding with the semi-dwarfing Rht-B1 locus. The effect of Rht-B1 alleles on anther extrusion is genotype dependent, while tall plant Rht-B1a allele is consistently associated with large anthers. Multiple QTLs were identified at the Ppd-D1 locus for anther length, spikelet number and spike length, with the photoperiod-sensitive Ppd-D1b allele associated with favourable pollinator traits in the populations studied. We also demonstrated that homeoloci, Rht-D1 and Ppd-B1, influence anther length among other traits. These results suggest that combinations of Rht-B1 and Ppd-D1 alleles control multiple pollinator traits and should be major targets of hybrid wheat breeding programs.
Asunto(s)
Flores/genética , Polinización/genética , Sitios de Carácter Cuantitativo , Triticum/genética , Alelos , Mapeo Cromosómico , Genes de Plantas , Genotipo , Fenotipo , FotoperiodoRESUMEN
BACKGROUND: In flowering plants, lipid biosynthesis and transport within anthers is essential for male reproductive success. TaMs1, a dominant wheat fertility gene located on chromosome 4BS, has been previously fine mapped and identified to encode a glycosylphosphatidylinositol (GPI)-anchored non-specific lipid transfer protein (nsLTP). Although this gene is critical for pollen exine development, details of its function remains poorly understood. RESULTS: In this study, we report that TaMs1 is only expressed from the B sub-genome, with highest transcript abundance detected in anthers containing microspores undergoing pre-meiosis through to meiosis. ß-glucuronidase transcriptional fusions further revealed that TaMs1 is expressed throughout all anther cell-types. TaMs1 was identified to be expressed at an earlier stage of anther development relative to genes reported to be necessary for sporopollenin precursor biosynthesis. In anthers missing a functional TaMs1 (ms1c deletion mutant), these same genes were not observed to be mis-regulated, indicating an independent function for TaMs1 in pollen development. Exogenous hormone treatments on GUS reporter lines suggest that TaMs1 expression is increased by both indole-3-acetic acid (IAA) and abscisic acid (ABA). Translational fusion constructs showed that TaMs1 is targeted to the plasma membrane. CONCLUSIONS: In summary, TaMs1 is a wheat fertility gene, expressed early in anther development and encodes a GPI-LTP targeted to the plasma membrane. The work presented provides a new insight into the process of wheat pollen development.
Asunto(s)
Glicosilfosfatidilinositoles/metabolismo , Metabolismo de los Lípidos/genética , Proteínas de Plantas/genética , Polen/crecimiento & desarrollo , Factores de Transcripción/genética , Triticum/genética , Ácido Abscísico/metabolismo , Flores/crecimiento & desarrollo , Flores/metabolismo , Perfilación de la Expresión Génica , Ácidos Indolacéticos/metabolismo , Reguladores del Crecimiento de las Plantas/metabolismo , Proteínas de Plantas/metabolismo , Polen/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Factores de Transcripción/metabolismo , Triticum/metabolismoRESUMEN
Bread wheat is strongly autogamous; however, an opportunity for outcrossing occurs when self-pollination fails and florets open. The first phase of floret opening at anthesis is short and induced by lodicule turgidity. Some wheat florets re-open post-anthesis for several days, known as the 'second opening', for which the underlying mechanisms are largely unknown. We performed detailed physiological, anatomical, and histological investigations to understand the biological basis of the flower opening process. Wheat florets were observed open when the ovary was unfertilized. Unfertilized ovaries significantly increased in radial size post-anthesis, pushing the lemma and palea apart to open the florets. The absence of fertile pollen was not directly linked to this, but anther filament elongation coincided with initiation of ovary swelling. The pericarp of unfertilized ovaries did not undergo degeneration as normally seen in developing grains, instead pericarp cells remained intact and enlarged, leading to increased ovary radial size. This is a novel role for the ovary pericarp in wheat flower opening, and the knowledge is useful for facilitating cross-pollination in hybrid breeding. Ovary swelling may represent a survival mechanism in autogamous cereals such as wheat and barley, ensuring seed set in the absence of self-fertilization and increasing genetic diversity through cross-pollination.
Asunto(s)
Flores/fisiología , Polinización/fisiología , Triticum/fisiología , FertilizaciónRESUMEN
Drought is one of the major abiotic stresses reducing crop yield. Since the discovery of plant microRNAs (miRNAs), considerable progress has been made in clarifying their role in plant responses to abiotic stresses, including drought. miR827 was previously reported to confer drought tolerance in transgenic Arabidopsis. We examined barley (Hordeum vulgare L. 'Golden Promise') plants over-expressing miR827 for plant performance under drought. Transgenic plants constitutively expressing CaMV-35S::Ath-miR827 and drought-inducible Zm-Rab17::Hv-miR827 were phenotyped by non-destructive imaging for growth and whole plant water use efficiency (WUEwp). We observed that the growth, WUEwp, time to anthesis and grain weight of transgenic barley plants expressing CaMV-35S::Ath-miR827 were negatively affected in both well-watered and drought-treated growing conditions compared with the wild-type plants. In contrast, transgenic plants over-expressing Zm-Rab17::Hv-miR827 showed improved WUEwp with no growth or reproductive timing change compared with the wild-type plants. The recovery of Zm-Rab17::Hv-miR827 over-expressing plants also improved following severe drought stress. Our results suggest that Hv-miR827 has the potential to improve the performance of barley under drought and that the choice of promoter to control the timing and specificity of miRNA expression is critical.
Asunto(s)
Adaptación Fisiológica , Sequías , Hordeum/genética , Plantas Modificadas GenéticamenteRESUMEN
Tetrapyrroles such as chlorophyll and heme play a vital role in primary plant metabolic processes such as photosynthesis and respiration. Over the past decades, extensive genetic and molecular analyses have provided valuable insights into the complex regulatory network of the tetrapyrrole biosynthesis. However, tetrapyrroles are also implicated in abiotic stress tolerance, although the mechanisms are largely unknown. With recent reports demonstrating that modified tetrapyrrole biosynthesis in plants confers wilting avoidance, a component physiological trait to drought tolerance, it is now timely that this pathway be reviewed in the context of drought stress signalling. In this review, the significance of tetrapyrrole biosynthesis under drought stress is addressed, with particular emphasis on the inter-relationships with major stress signalling cascades driven by reactive oxygen species (ROS) and organellar retrograde signalling. We propose that unlike the chlorophyll branch, the heme branch of the pathway plays a key role in mediating intracellular drought stress signalling and stimulating ROS detoxification under drought stress. Determining how the tetrapyrrole biosynthetic pathway is involved in stress signalling provides an opportunity to identify gene targets for engineering drought-tolerant crops.
Asunto(s)
Sequías , Fenómenos Fisiológicos de las Plantas , Transducción de Señal , Estrés Fisiológico , Tetrapirroles/metabolismo , Especies Reactivas de Oxígeno/metabolismoRESUMEN
Fusarium head blight (FHB) is a devastating wheat disease. Fhb1, the most widely applied genetic locus for FHB resistance, is conferred by TaHRC of an unknown mode of action. Here, we show that TaHRC alleles distinctly drive liquid-liquid phase separation (LLPS) within a proteinaceous complex, determining FHB susceptibility or resistance. TaHRC-S (susceptible) exhibits stronger LLPS ability than TaHRC-R (resistant), and this distinction is further intensified by fungal mycotoxin deoxynivalenol, leading to opposing FHB symptoms. TaHRC recruits a protein class with intrinsic LLPS potentials, referred to as an "HRC-containing hub." TaHRC-S drives condensation of hub components, while TaHRC-R comparatively suppresses hub condensate formation. The function of TaSR45a splicing factor, a hub member, depends on TaHRC-driven condensate state, which in turn differentially directs alternative splicing, switching between susceptibility and resistance to wheat FHB. These findings reveal a mechanism for FHB spread within a spike and shed light on the roles of complex condensates in controlling plant disease.
Asunto(s)
Resistencia a la Enfermedad , Fusarium , Enfermedades de las Plantas , Proteínas de Plantas , Triticum , Triticum/microbiología , Triticum/genética , Triticum/metabolismo , Fusarium/genética , Enfermedades de las Plantas/microbiología , Resistencia a la Enfermedad/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Tricotecenos/metabolismo , Alelos , Empalme AlternativoRESUMEN
Global food security demands the development and delivery of new technologies to increase and secure cereal production on finite arable land without increasing water and fertilizer use. There are several options for boosting wheat yields, but most offer only small yield increases. Wheat is an inbred plant, and hybrids hold the potential to deliver a major lift in yield and will open a wide range of new breeding opportunities. A series of technological advances are needed as a base for hybrid wheat programmes. These start with major changes in floral development and architecture to separate the sexes and force outcrossing. Male sterility provides the best method to block self-fertilization, and modifying the flower structure will enhance pollen access. The recent explosion in genomic resources and technologies provides new opportunities to overcome these limitations. This review outlines the problems with existing hybrid wheat breeding systems and explores molecular-based technologies that could improve the hybrid production system to reduce hybrid seed production costs, a prerequisite for a commercial hybrid wheat system.
Asunto(s)
Cruzamiento/métodos , Semillas/genética , Triticum/genética , Quimera , Productos Agrícolas/genética , Flores/genética , Flores/fisiología , Vigor Híbrido , Infertilidad Vegetal/genética , Plantas Modificadas Genéticamente , AutofecundaciónRESUMEN
The CLAVATA3/embryo-surrounding region (CLE) peptides control the fine balance between proliferation and differentiation in plant development. We studied the role of CLE peptides during indeterminate nodule development and identified 25 MtCLE peptide genes in the Medicago truncatula genome, of which two genes, MtCLE12 and MtCLE13, had nodulation-related expression patterns that were linked to proliferation and differentiation. MtCLE13 expression was up-regulated early in nodule development. A high-to-low expression gradient radiated from the inner toward the outer cortical cell layers in a region defining the incipient nodule. At later stages, MtCLE12 and MtCLE13 were expressed in differentiating nodules and in the apical part of mature, elongated nodules. Functional analysis revealed a putative role for MtCLE12 and MtCLE13 in autoregulation of nodulation, a mechanism that controls the number of nodules and involves systemic signals mediated by a leucine-rich repeat receptor-like kinase, SUNN, which is active in the shoot. When MtCLE12 and MtCLE13 were ectopically expressed in transgenic roots, nodulation was abolished at the level of the nodulation factor signal transduction, and this inhibition involved long-distance signaling. In addition, composite plants with roots ectopically expressing MtCLE12 or MtCLE13 had elongated petioles. This systemic effect was not observed in transgenic roots ectopically expressing MtCLE12 and MtCLE13 in a sunn-1 mutant background, although nodulation was still strongly reduced. These results suggest multiple roles for CLE signaling in nodulation.
Asunto(s)
Medicago truncatula/crecimiento & desarrollo , Proteínas de Plantas/metabolismo , Nodulación de la Raíz de la Planta , Citocininas/metabolismo , Expresión Génica , Genes de Plantas , Ácidos Indolacéticos/metabolismo , Medicago truncatula/genética , Medicago truncatula/metabolismo , Mutación , Péptidos/metabolismo , Proteínas de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Brotes de la Planta/metabolismo , Regulación hacia ArribaRESUMEN
The Clavata3 (CLV3)/endosperm surrounding region (CLE) signaling peptides are encoded in large plant gene families. CLV3 and the other A-type CLE peptides promote cell differentiation in root and shoot apical meristems, whereas the B-type peptides (CLE41-CLE44) do not. Instead, CLE41 inhibits the differentiation of Zinnia elegans tracheary elements. To test whether CLE genes might code for antagonistic or synergistic functions, peptides from both types were combined through overexpression within or application onto Arabidopsis thaliana seedlings. The CLE41 peptide (CLE41p) promoted proliferation of vascular cells, although delaying differentiation into phloem and xylem cell lineages. Application of CLE41p or overexpression of CLE41 did not suppress the terminal differentiation of the root and shoot apices triggered by A-type CLE peptides. However, in combination, A-type peptides enhanced all of the phenotypes associated with CLE41 gain-of-function, leading to massive proliferation of vascular cells. This proliferation relied on auxin signaling because it was enhanced by exogenous application of a synthetic auxin, decreased by an auxin polar transport inhibitor, and abolished by a mutation in the Monopteros auxin response factor. These findings highlight that vascular patterning is a process controlled in time and space by different CLE peptides in conjunction with hormonal signaling.
Asunto(s)
División Celular , Péptidos/fisiología , Células Vegetales , Fenómenos Fisiológicos de las Plantas , Proteínas de Plantas/fisiología , Linaje de la Célula , Desarrollo de la Planta , Proteínas de Plantas/químicaRESUMEN
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.
Asunto(s)
ADN de Plantas/genética , Regulación de la Expresión Génica de las Plantas , Recombinación Homóloga , Fitomejoramiento/métodos , Proteínas de Plantas/genética , Triticum/genética , Alelos , Quimera , Cromosomas de las Plantas/química , Reparación de la Incompatibilidad de ADN , ADN de Plantas/metabolismo , Meiosis , Mutación , Mapeo Físico de Cromosoma , Proteínas de Plantas/metabolismo , Ploidias , Secale/genética , Secale/metabolismo , Triticum/metabolismoRESUMEN
Hybrid breeding in wheat has the potential to boost yields. An efficient hybrid seed production system requires elite pollinators; however, such germplasm is limited among modern cultivars. Piko, a winter wheat (Triticum aestivum L.) cultivar, has been identified as a superior pollinator and has been used in Europe. Piko has favourable pollinator traits for anther extrusion, anther length, pollen mass and hybrid seed set. However, the genetic factors responsible for Piko's favourable traits are largely unknown. Here, we report on the genetic analysis of a Piko-derived F2 mapping population. We confirmed that Piko's Rht-D1a allele for tall stature is associated with large anthers and high anther extrusion. However, Rht-D1 was not found to be associated with anther filament length, confirmed by near isogenic lines. Piko's photoperiod sensitive Ppd-B1b allele shows an association with increased spike length, more spikelets and spike architecture traits, while the insensitive Ppd-B1a allele is linked with high anther extrusion and larger anthers. We identified an anther extrusion quantitative trait locus (QTL) on chromosome 6A that showed significantly biased transmission of the favourable Piko allele amongst F2 progenies. The Piko allele is completely absent in the distal 6AS region and the central 6A region revealed a significantly lower ratio (<8%) of F2 with homozygous Piko alleles. Our study provided further evidence for the effects of Rht-D1 and Ppd-B1 loci on multiple pollinator traits and a novel anther extrusion QTL that exhibits segregation distortion.
Asunto(s)
Fitomejoramiento , Triticum , Europa (Continente) , Fenotipo , Sitios de Carácter Cuantitativo/genética , Triticum/genéticaRESUMEN
Hybrid breeding in wheat (Triticum aestivum L.) has the potential to deliver major yield increases. This is a requisite to guarantee food security for increasing population demands and to counterbalance the effects of extreme environmental conditions. Successful hybrid breeding in wheat relies on forced outcrossing while preventing self-pollination. To achieve this, research has been directed towards identifying and improving fertility control systems. To maximise cross-pollination and seed set, however, fertility control systems need to be complemented by breeding phenotypically distinct male and female lines. This review summarises existing and novel male sterility systems for wheat hybridisation. We also consider the genetic resources that can be used to alter wheat's floral development and spike morphology, with a focus on the genetic variation already available. Exploiting these resources can lead to enhanced outcrossing, a key requirement in the progress towards hybrid wheat breeding.
Asunto(s)
Fitomejoramiento , Triticum , Biología , Femenino , Hibridación Genética , Masculino , Semillas , Triticum/genéticaRESUMEN
Non-specific Lipid Transfer Proteins (nsLTPs) are involved in numerous biological processes. To date, only a fraction of wheat (Triticum aestivum L.) nsLTPs (TaLTPs) have been identified, and even fewer have been functionally analysed. In this study, the identification, classification, phylogenetic reconstruction, chromosome distribution, functional annotation and expression profiles of TaLTPs were analysed. 461 putative TaLTPs were identified from the wheat genome and classified into five types (1, 2, C, D and G). Phylogenetic analysis of the TaLTPs along with nsLTPs from Arabidopsis thaliana and rice, showed that all five types were shared across species, however, some type 2 TaLTPs formed wheat-specific clades. Gene duplication analysis indicated that tandem duplications contributed to the expansion of this gene family in wheat. Analysis of RNA sequencing data showed that TaLTPs were expressed in most tissues and stages of wheat development. Further, we refined the expression profile of anther-enriched expressed genes, and identified potential cis-elements regulating their expression specificity. This analysis provides a valuable resource towards elucidating the function of TaLTP family members during wheat development, aids our understanding of the evolution and expansion of the TaLTP gene family and, additionally, provides new information for developing wheat male-sterile lines with application to hybrid breeding.