RESUMO
KEY MESSAGE: A Bayesian linkage disequilibrium-based multiple-locus mixed model identified QTLs for fibre, seed and oil traits and predicted breeding worthiness of test lines, enabling their simultaneous improvement in cotton. Improving cotton seed and oil yields has become increasingly important while continuing to breed for higher lint yield. In this study, a novel Bayesian linkage disequilibrium-based multiple-locus mixed model was developed for QTL identification and genomic prediction (GP). A multi-parent population consisting of 256 recombinant inbred lines, derived from four elite cultivars with distinct combinations of traits, was used in the analysis of QTLs for lint percentage, seed index, lint index and seed oil content and their interrelations. All four traits were moderately heritable and correlated but with no large influence of genotype × environment interactions across multiple seasons. Seven to ten major QTLs were identified for each trait with many being adjacent or overlapping for different trait pairs. A fivefold cross-validation of the model indicated prediction accuracies of 0.46-0.62. GP results based on any two-season phenotypes were strongly correlated with phenotypic means of a pooled analysis of three-season experiments (r = 0.83-0.92). When used for selection of improvement in lint, seed and oil yields, GP captured 40-100% of individuals with comparable lint yields of those selected based on the three-season phenotypic results. Thus, this quantitative genomics-enabled approach can not only decipher the genomic variation underlying lint, seed and seed oil traits and their interrelations, but can provide predictions for their simultaneous improvement. We discuss future breeding strategies in cotton that will enhance the entire value of the crop, not just its fibre.
Assuntos
Teorema de Bayes , Gossypium , Desequilíbrio de Ligação , Fenótipo , Melhoramento Vegetal , Locos de Características Quantitativas , Sementes , Gossypium/genética , Gossypium/crescimento & desenvolvimento , Sementes/genética , Sementes/crescimento & desenvolvimento , Melhoramento Vegetal/métodos , Genótipo , Genômica/métodos , Mapeamento Cromossômico/métodos , Fibra de Algodão/análise , Modelos Genéticos , Seleção GenéticaRESUMO
Some plant microRNA (miRNA) families contain multiple members generating identical or highly similar mature miRNA variants. Mechanisms underlying the expansion of miRNA families remain elusive, although tandem and/or segmental duplications have been proposed. In this study of two tetraploid cottons, Gossypium hirsutum and Gossypium barbadense, and their extant diploid progenitors, Gossypium arboreum and Gossypium raimondii, we investigated the gain and loss of members of the miR482/2118 superfamily, which modulates the expression of nucleotide-binding site leucine-rich repeat (NBS-LRR) disease resistance genes. We found significant expansion of MIR482/2118d in G. barbadense, G. hirsutum and G. raimondii, but not in G. arboreum. Several newly expanded MIR482/2118d loci have mutated to produce different miR482/2118 variants with altered target-gene specificity. Based on detailed analysis of sequences flanking these MIR482/2118 loci, we found that this expansion of MIR482/2118d and its derivatives resulted from an initial capture of an MIR482/2118d by a class-II DNA transposable element (TE) in G. raimondii prior to the tetraploidization event, followed by transposition to new genomic locations in G. barbadense, G. hirsutum and G. raimondii. The 'GosTE' involved in the capture and proliferation of MIR482/2118d and its derivatives belongs to the PIF/Harbinger superfamily, generating a 3-bp target site duplication upon insertion at new locations. All orthologous MIR482/2118 loci in the two diploids were retained in the two tetraploids, but mutation(s) in miR482/2118 were observed across all four species as well as in different cultivars of both G. barbadense and G. hirsutum, suggesting a dynamic co-evolution of miR482/2118 and its NBS-LRR targets. Our results provide fresh insights into the mechanisms contributing to MIRNA proliferation and enrich our knowledge on TEs.
Assuntos
Elementos de DNA Transponíveis/genética , Gossypium/genética , MicroRNAs/genética , RNA de Plantas/genética , Gossypium/metabolismo , MicroRNAs/metabolismo , RNA de Plantas/metabolismo , Sequências Repetitivas de Ácido Nucleico/genética , TetraploidiaRESUMO
Black root rot (BRR) is an economically important disease of cotton and other crops, especially in cooler regions with short growing seasons. Symptoms include black discoloration of the roots, reduced number of lateral roots and stunted or slow plant growth. The cultivated tetraploid Gossypium species are susceptible to BRR. Resistance to BRR was identified in G. arboreum accession BM13H and is associated with reduced and restricted hyphal growth and less sporulation. Transcriptome analysis indicates that BM13H responds to infection at early time points 2- and 3-days post-inoculation, but by day 5, few differentially expressed genes are observed between infected and uninfected roots. Inheritance of BM13H resistance to BRR was evaluated in an F6 recombinant inbred population and shows a single semi-dominant locus conferring resistance that was fine mapped to a region on chromosome 1, containing ten genes including five putative resistance-like genes.
Assuntos
Ascomicetos/metabolismo , Mapeamento Cromossômico , Resistência à Doença/genética , Gossypium , Doenças das Plantas , Raízes de Plantas , Regulação da Expressão Gênica de Plantas , Gossypium/genética , Gossypium/metabolismo , Gossypium/microbiologia , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , TetraploidiaRESUMO
Many polypetalous plants have a constriction at the base of the petal that leaves a small gap that can provide entry into the young flower bud before the reproductive organs are fully developed. In cotton (Gossypium hirsutum L.), this gap is occluded by tufts of short unicellular trichomes superficially resembling the fibers found on cotton seeds. We are just beginning to understand the developmental regulation of the seed fibers and have previously characterized several MIXTA-like MYB transcription factors (TFs) that are critical for correct seed fiber development but know little about the molecular regulation of other types of cotton trichomes. Here, using RNAi or dominant suppression transgenic cotton lines and natural fiber mutants, we investigated the development and regulation of the petal base trichomes. Petal base trichomes and seed trichomes were also examined across several different species within and outside of the Malvoideae. We found that the petal base trichomes are regulated by the same MYB TFs as cotton seed fibers and, since they are more widely distributed across different taxa than the seed fibers, could have preceded them in the evolution of these important textile fibers produced by some cotton species.
Assuntos
Flores/metabolismo , Gossypium/metabolismo , Proteínas de Plantas/fisiologia , Sementes/metabolismo , Fatores de Transcrição/fisiologia , Tricomas/metabolismo , Fibra de Algodão , Flores/fisiologia , Gossypium/fisiologia , Proteínas de Plantas/metabolismo , Proteínas Proto-Oncogênicas c-myb/metabolismo , Proteínas Proto-Oncogênicas c-myb/fisiologia , Sementes/fisiologia , Fatores de Transcrição/metabolismo , Tricomas/fisiologiaRESUMO
Alpha-linolenic acid (ALA, 18:3Δ9,12,15) and γ-linolenic acid \ (GLA, 18:3Δ6,9,12) are important trienoic fatty acids, which are beneficial for human health in their own right, or as precursors for the biosynthesis of long-chain polyunsaturated fatty acids. ALA and GLA in seed oil are synthesized from linoleic acid (LA, 18:2Δ9,12) by the microsomal ω-3 fatty acid desaturase (FAD3) and Δ6 desaturase (D6D), respectively. Cotton (Gossypium hirsutum L.) seed oil composition was modified by transforming with an FAD3 gene from Brassica napus and a D6D gene from Echium plantagineum, resulting in approximately 30% ALA and 20% GLA, respectively. The total oil content in transgenic seeds remained unaltered relative to parental seeds. Despite the use of a seed-specific promoter for transgene expression, low levels of GLA and increased levels of ALA were found in non-seed cotton tissues. At low temperature, the germinating cottonseeds containing the linolenic acid isomers elongated faster than the untransformed controls. ALA-producing lines also showed higher photosynthetic rates at cooler temperature and better fiber quality compared to both untransformed controls and GLA-producing lines. The oxidative stability of the novel cottonseed oils was assessed, providing guidance for potential food, pharmaceutical and industrial applications of these oils.
Assuntos
Fibra de Algodão , Óleo de Sementes de Algodão/metabolismo , Germinação/genética , Gossypium/genética , Fotossíntese/genética , Sementes/crescimento & desenvolvimento , Ácido alfa-Linolênico/metabolismo , Ácido gama-Linolênico/metabolismo , Brassica napus/genética , Resposta ao Choque Frio , Fibra de Algodão/normas , Ácidos Graxos Dessaturases/genética , Ácidos Graxos Dessaturases/metabolismo , Engenharia Genética , Gossypium/metabolismo , Plantas Geneticamente Modificadas , Sementes/metabolismo , Ácido alfa-Linolênico/genética , Ácido gama-Linolênico/genéticaRESUMO
Only a few transcription factors (TFs) regulating which cells of the ovule epidermis differentiate into lint fibres have been identified in cotton (Gossypium hirsutum L.). In this study, the effect on lint yield and fibre quality of over-expressing three TFs in cotton, GhHD-1, GhMYB25 and GhMYB25Like, and their double and triple combinations, were evaluated in field experiments over two seasons. The expression of single or stacked TFs were all driven either by an ovule-specific promoter, FBP 7, or a constitutive promoter, Stunt 7, in a Coker 315 background. TF type, either singly or in combination, was found to be the most significant factor affecting lint yield. Among 64 transgenic lines tested, seven were higher yielding than null segregant lines in one or both seasons and were all from the sets with single and double over-expressed TF combinations. A reduced yield was associated with the set of triple combinations. The two most stable high yielding lines across the seasons recorded 12-22% higher yields than the nulls, although were not competitive to locally adapted commercial controls. Over-expression of TFs singly or in combination did not significantly alter fibre length and strength, but sometimes increased fibre micronaire. There were positive relationships between lint yield and lint percentage and lint yield and fibre density amongst the transgenic lines. Our preliminary results suggest that manipulating TF expression, either singly or in pairs, can increase the density of fibres initiated on developing seeds and fibre yields under field conditions while maintaining overall fibre quality.
Assuntos
Gossypium/genética , Plantas Geneticamente Modificadas/genética , Fatores de Transcrição/genética , Fibra de Algodão , Regulação da Expressão Gênica de Plantas , Gossypium/crescimento & desenvolvimento , Óvulo Vegetal/genética , Óvulo Vegetal/crescimento & desenvolvimento , Proteínas de Plantas/genética , Regiões Promotoras Genéticas , Sementes/genéticaRESUMO
Due to an unfortunate misunderstanding, an extra middle initial erroneously appeared in the original publication and the full name of the first author should read Shi Ming Liu.
RESUMO
Upon publication of the original article [1], the authors had flagged that Fig. 1 had been published twice, as both Fig. 1 and Additional file 3.
RESUMO
Cotton fibres are single-celled trichomes arising from the epidermal cells of the seed coat and may be either long (lint) or very short (fuzz). The dominant fuzzless N1 of Gossypium hirsutum is a defective allele of the At-subgenome homoeolog of MYB25-like, but the genetic components underlying the recessive fuzzless trait from G. barbadense (Gb) are unknown. We have identified five genetic loci, including a major contributing locus containing MYB25-like_Dt, associated with Gb fuzzless seeds based on genotyping of fuzzy and fuzzless near isogenic lines (NILs) from an interspecies cross (G. barbadense × G. hirsutum). At 3 d post-anthesis when fuzz fibres are initiating, expression of MYB25-like_Dt was significantly lower in fuzzless NILs than in fuzzy seeded NILs, while higher MYB25-like_Dt expression was associated with more seed fuzz across different cotton genotypes. Phenotypic and genotypic analysis of MYB25-like homoeoalleles in cottons showing different fibre phenotypes and their crossing progeny indicated that both MYB25-like_At and MYB25-like_Dt are associated with lint development, and that fuzz development is mainly determined by the expression level of MYB25-like_Dt at ~3 d post-anthesis. Expression of Gb fuzzless seeds depends on genetic background and interactions amongst the multiple loci identified. MYB25-like_Dt is one of the best candidates for N2.
Assuntos
Genótipo , Gossypium/genética , Fenótipo , Proteínas de Plantas/genética , Sementes/crescimento & desenvolvimento , Gossypium/crescimento & desenvolvimento , Gossypium/metabolismo , Proteínas de Plantas/metabolismo , Sementes/genética , Sementes/metabolismoRESUMO
Polyploidy often confers emergent properties, such as the higher fibre productivity and quality of tetraploid cottons than diploid cottons bred for the same environments. Here we show that an abrupt five- to sixfold ploidy increase approximately 60 million years (Myr) ago, and allopolyploidy reuniting divergent Gossypium genomes approximately 1-2 Myr ago, conferred about 30-36-fold duplication of ancestral angiosperm (flowering plant) genes in elite cottons (Gossypium hirsutum and Gossypium barbadense), genetic complexity equalled only by Brassica among sequenced angiosperms. Nascent fibre evolution, before allopolyploidy, is elucidated by comparison of spinnable-fibred Gossypium herbaceum A and non-spinnable Gossypium longicalyx F genomes to one another and the outgroup D genome of non-spinnable Gossypium raimondii. The sequence of a G. hirsutum A(t)D(t) (in which 't' indicates tetraploid) cultivar reveals many non-reciprocal DNA exchanges between subgenomes that may have contributed to phenotypic innovation and/or other emergent properties such as ecological adaptation by polyploids. Most DNA-level novelty in G. hirsutum recombines alleles from the D-genome progenitor native to its New World habitat and the Old World A-genome progenitor in which spinnable fibre evolved. Coordinated expression changes in proximal groups of functionally distinct genes, including a nuclear mitochondrial DNA block, may account for clusters of cotton-fibre quantitative trait loci affecting diverse traits. Opportunities abound for dissecting emergent properties of other polyploids, particularly angiosperms, by comparison to diploid progenitors and outgroups.
Assuntos
Evolução Biológica , Fibra de Algodão , Genoma de Planta/genética , Gossypium/genética , Poliploidia , Alelos , Cacau/genética , Cromossomos de Plantas/genética , Diploide , Duplicação Gênica/genética , Genes de Plantas/genética , Gossypium/classificação , Anotação de Sequência Molecular , Filogenia , Vitis/genéticaRESUMO
BACKGROUND: Knowledge of plant secondary cell wall (SCW) regulation and deposition is mainly based on the Arabidopsis model of a 'typical' lignocellulosic SCW. However, SCWs in other plants can vary from this. The SCW of mature cotton seed fibres is highly cellulosic and lacks lignification whereas xylem SCWs are lignocellulosic. We used cotton as a model to study different SCWs and the expression of the genes involved in their formation via RNA deep sequencing and chemical analysis of stem and seed fibre. RESULTS: Transcriptome comparisons from cotton xylem and pith as well as from a developmental series of seed fibres revealed tissue-specific and developmentally regulated expression of several NAC transcription factors some of which are likely to be important as top tier regulators of SCW formation in xylem and/or seed fibre. A so far undescribed hierarchy was identified between the top tier NAC transcription factors SND1-like and NST1/2 in cotton. Key SCW MYB transcription factors, homologs of Arabidopsis MYB46/83, were practically absent in cotton stem xylem. Lack of expression of other lignin-specific MYBs in seed fibre relative to xylem could account for the lack of lignin deposition in seed fibre. Expression of a MYB103 homolog correlated with temporal expression of SCW CesAs and cellulose synthesis in seed fibres. FLAs were highly expressed and may be important structural components of seed fibre SCWs. Finally, we made the unexpected observation that cell walls in the pith of cotton stems contained lignin and had a higher S:G ratio than in xylem, despite that tissue's lacking many of the gene transcripts normally associated with lignin biosynthesis. CONCLUSIONS: Our study in cotton confirmed some features of the currently accepted gene regulatory cascade for 'typical' plant SCWs, but also revealed substantial differences, especially with key downstream NACs and MYBs. The lignocellulosic SCW of cotton xylem appears to be achieved differently from that in Arabidopsis. Pith cell walls in cotton stems are compositionally very different from that reported for other plant species, including Arabidopsis. The current definition of a 'typical' primary or secondary cell wall might not be applicable to all cell types in all plant species.
Assuntos
Parede Celular/metabolismo , Perfilação da Expressão Gênica , Gossypium/citologia , Gossypium/genética , Celulose/biossíntese , Gossypium/metabolismo , Especificidade de Órgãos , Caules de Planta/crescimento & desenvolvimento , Caules de Planta/metabolismo , Propanóis/metabolismo , Fatores de Transcrição/metabolismo , Transcrição GênicaRESUMO
BACKGROUND: Cotton germplasm resources contain beneficial alleles that can be exploited to develop germplasm adapted to emerging environmental and climate conditions. Accessions and lines have traditionally been characterized based on phenotypes, but phenotypic profiles are limited by the cost, time, and space required to make visual observations and measurements. With advances in molecular genetic methods, genotypic profiles are increasingly able to identify differences among accessions due to the larger number of genetic markers that can be measured. A combination of both methods would greatly enhance our ability to characterize germplasm resources. Recent efforts have culminated in the identification of sufficient SNP markers to establish high-throughput genotyping systems, such as the CottonSNP63K array, which enables a researcher to efficiently analyze large numbers of SNP markers and obtain highly repeatable results. In the current investigation, we have utilized the SNP array for analyzing genetic diversity primarily among cotton cultivars, making comparisons to SSR-based phylogenetic analyses, and identifying loci associated with seed nutritional traits. RESULTS: The SNP markers distinctly separated G. hirsutum from other Gossypium species and distinguished the wild from cultivated types of G. hirsutum. The markers also efficiently discerned differences among cultivars, which was the primary goal when designing the CottonSNP63K array. Population structure within the genus compared favorably with previous results obtained using SSR markers, and an association study identified loci linked to factors that affect cottonseed protein content. CONCLUSIONS: Our results provide a large genome-wide variation data set for primarily cultivated cotton. Thousands of SNPs in representative cotton genotypes provide an opportunity to finely discriminate among cultivated cotton from around the world. The SNPs will be relevant as dense markers of genome variation for association mapping approaches aimed at correlating molecular polymorphisms with variation in phenotypic traits, as well as for molecular breeding approaches in cotton.
Assuntos
Gossypium/genética , Polimorfismo de Nucleotídeo Único , Alelos , Marcadores Genéticos , Variação Genética , Genoma de Planta , Genótipo , Gossypium/classificação , Repetições de Microssatélites , Filogenia , Proteínas de Plantas/genéticaRESUMO
Cotton provides us the most important natural fibre. High fibre quality is the major goal of cotton breeding, and introducing genes conferring longer, finer and stronger fibre from Gossypium barbadense to Gossypium hirsutum is an important breeding strategy. We previously analysed the G. barbadense fibre development mechanism by gene expression profiling and found two homoeologous fibre-specific α-expansins from G. barbadense, GbEXPA2 and GbEXPATR. GbEXPA2 (from the DT genome) is a classical α-expansin, while its homoeolog, GbEXPATR (AT genome), encodes a truncated protein lacking the normal C-terminal polysaccharide-binding domain of other α-expansins and is specifically expressed in G. barbadense. Silencing EXPA in G. hirsutum induced shorter fibres with thicker cell walls. GbEXPA2 overexpression in G. hirsutum had no effect on mature fibre length, but produced fibres with a slightly thicker wall and increased crystalline cellulose content. Interestingly, GbEXPATR overexpression resulted in longer, finer and stronger fibres coupled with significantly thinner cell walls. The longer and thinner fibre was associated with lower expression of a number of secondary wall-associated genes, especially chitinase-like genes, and walls with lower cellulose levels but higher noncellulosic polysaccharides which advocated that a delay in the transition to secondary wall synthesis might be responsible for better fibre. In conclusion, we propose that α-expansins play a critical role in fibre development by loosening the cell wall; furthermore, a truncated form, GbEXPATR, has a more dramatic effect through reorganizing secondary wall synthesis and metabolism and should be a candidate gene for developing G. hirsutum cultivars with superior fibre quality.
Assuntos
Parede Celular/metabolismo , Fibra de Algodão , Proteínas de Plantas/metabolismo , Sequência de Bases , Parede Celular/genética , Cruzamentos Genéticos , Regulação para Baixo/genética , Genes de Plantas , Teste de Complementação Genética , Proteínas de Plantas/química , Plantas Geneticamente Modificadas , Polimorfismo de Nucleotídeo Único/genética , Domínios Proteicos , Homologia de Sequência do Ácido Nucleico , Especificidade da EspécieRESUMO
Diverse leaf morphology has been observed among accessions of Gossypium hirsutum, including okra leaf, which has advantages and disadvantages in cotton production. The okra leaf locus has been mapped to chromosome 15 of the Dt subgenome, but the underlying gene has yet to be identified. In this study, we used a combination of targeted association analysis, F2 population-based fine mapping, and comparative sequencing of orthologues to identify a candidate gene underlying the okra leaf trait in G. hirsutum. The okra leaf gene identified, GhOKRA, encoded a homeodomain leucine-zipper class I protein, whose closely related genes in several other plant species have been shown to be involved in regulating leaf morphology. The transcript levels of GhOKRA in shoot apices were positively correlated with the phenotypic expression of the okra leaf trait. Of the multiple sequence variations observed in the coding region among GrOKRA of Gossypium raimondii and GhOKRA-Dt of normal and okra/superokra leaf G. hirsutum accessions, a non-synonymous substitution near the N terminus and the variable protein sequences at the C terminus may be related to the leaf shape difference. Our results suggest that both transcription and protein activity of GhOKRA may be involved in regulating leaf shape. Furthermore, we found that non-reciprocal homoeologous recombination, or gene conversion, may have played a role in the origin of the okra leaf allele. Our results provided tools for further investigating and understanding the fundamental biological processes that are responsible for the cotton leaf shape variation and will help in the design of cotton plants with an ideal leaf shape for enhanced cotton production.
Assuntos
Abelmoschus/anatomia & histologia , Mapeamento Cromossômico/métodos , Genes de Plantas , Gossypium/anatomia & histologia , Gossypium/genética , Folhas de Planta/anatomia & histologia , Característica Quantitativa Herdável , Alelos , Arabidopsis/genética , Cruzamentos Genéticos , Ecótipo , Regulação da Expressão Gênica de Plantas , Loci Gênicos , Fenótipo , Proteínas de Plantas/química , Proteínas de Plantas/genética , Análise de Sequência de ProteínaRESUMO
Gossypium hirsutum L. (cotton) fibres are specialized trichomes a few centimetres in length that grow from the seed coat. Few genes directly involved in the differentiation of these epidermal cells have been identified. These include GhMYB25-like and GhMYB25, two related MYB transcription factors that regulate fibre cell initiation and expansion. We have also identified a putative homeodomain leucine zipper (HD-ZIP) transcription factor, GhHD-1, expressed in trichomes and early fibres that might play a role in cotton fibre initiation. Here, we characterize GhHD-1 homoeologues from tetraploid G. hirsutum and show, using reporter constructs and quantitative real-time PCR (qRT-PCR), that they are expressed predominantly in epidermal tissues during early fibre development, and in other tissues bearing epidermal trichomes. Silencing of GhHD-1 reduced trichome formation and delayed the timing of fibre initiation. Constitutive overexpression of GhHD-1 increased the number of fibres initiating on the seed, but did not affect leaf trichomes. Expression of GhHD-1 in cotton silenced for different fibre MYBs suggest that in ovules it acts downstream of GhMYB25-like, but is unaffected in GhMYB25- or GhMYB109-silenced plants. Microarray analysis of silencing and overexpression lines of GhHD-1 indicated that it potentially regulates the levels of ethylene and reactive oxidation species (ROS) through a WRKY transcription factor and calcium-signalling pathway genes to activate downstream genes necessary for cell expansion and elongation.
Assuntos
Diferenciação Celular/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Gossypium/fisiologia , Epiderme Vegetal/fisiologia , Proteínas de Plantas/metabolismo , Sequência de Aminoácidos , Sinalização do Cálcio/fisiologia , Diferenciação Celular/fisiologia , Crescimento Celular , Fibra de Algodão , Etilenos/metabolismo , Regulação da Expressão Gênica de Plantas/genética , Genes Homeobox , Gossypium/citologia , Gossypium/genética , Gossypium/crescimento & desenvolvimento , Zíper de Leucina/genética , Dados de Sequência Molecular , Filogenia , Componentes Aéreos da Planta/citologia , Componentes Aéreos da Planta/genética , Componentes Aéreos da Planta/crescimento & desenvolvimento , Componentes Aéreos da Planta/fisiologia , Epiderme Vegetal/citologia , Epiderme Vegetal/genética , Epiderme Vegetal/crescimento & desenvolvimento , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas/genética , Espécies Reativas de Oxigênio/metabolismo , Sementes/citologia , Sementes/genética , Sementes/crescimento & desenvolvimento , Sementes/fisiologia , Alinhamento de Sequência , Fatores de Tempo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
MYB transcription factors have been implicated in regulation of the development of ovule epidermal cells into the elongated seed fibres of cotton. An R2R3 MYB, GhMYB25-like, identified from its reduced expression in a fibreless mutant of cotton (Xu142 fl), is here shown to play a key role in the very early stages of fibre cell differentiation. A GhMYB25-like promoter-GUS construct was expressed predominantly in the epidermal layers of cotton ovules before anthesis (-3days post-anthesis, dpa), increasing in expression in 0-dpa ovules, primarily in those epidermal cells expanding into fibres, and then in elongating fibres at +3dpa, declining thereafter. This was consistent with GhMYB25-like transcript abundance during fibre development. RNA interference suppression of GhMYB25-like resulted in cotton plants with fibreless seeds, but normal trichomes elsewhere, phenocopying the Xu142 fl mutant. Like Xu142 fl these plants had reduced expression of the fibre-expressed MYBs, GhMYB25 and GhMYB109, indicating that GhMYB25-like is upstream from those MYBs. This hierarchy was supported by the absence of any change in transcript level of GhMYB25-like in GhMYB25- and GhMYB109-silenced transgenic lines. Transgenic cotton with an additional copy of the native gene had elevated expression of GhMYB25-like in ovules, but no obvious increase in fibre initials, suggesting that there may be other factors that interact with GhMYB25-like to differentiate epidermal cells into fibre cells.
Assuntos
Gossypium/genética , Proteínas de Plantas/metabolismo , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , Clonagem Molecular , Fibra de Algodão , DNA de Plantas/genética , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Gossypium/metabolismo , Microscopia Eletrônica de Varredura , Dados de Sequência Molecular , Óvulo Vegetal/genética , Óvulo Vegetal/metabolismo , Óvulo Vegetal/ultraestrutura , Epiderme Vegetal/genética , Epiderme Vegetal/metabolismo , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Regiões Promotoras Genéticas , Interferência de RNA , Alinhamento de Sequência , Análise de Sequência de DNA , Fatores de Transcrição/genéticaRESUMO
Sucrose (Suc) synthase (Sus) is the major enzyme of Suc breakdown for cellulose biosynthesis in cotton (Gossypium hirsutum) fiber, an important source of fiber for the textile industry. This study examines the tissue-specific expression, relative abundance, and temporal expression of various Sus transcripts and proteins present in cotton. A novel isoform of Sus (SusC) is identified that is expressed at high levels during secondary cell wall synthesis in fiber and is present in the cell wall fraction. The phylogenetic relationships of the deduced amino acid sequences indicate two ancestral groups of Sus proteins predating the divergence of monocots and dicots and that SusC sequences form a distinct branch in the phylogeny within the dicot-specific clade. The subcellular location of the Sus isoforms is determined, and it is proposed that cell wall-localized SusC may provide UDP-glucose for cellulose and callose synthesis from extracellular sugars.
Assuntos
Parede Celular/enzimologia , Fibra de Algodão , Glucosiltransferases/metabolismo , Isoenzimas/metabolismo , Sequência de Aminoácidos , Genes de Plantas , Glucosiltransferases/química , Glucosiltransferases/genética , Gossypium/genética , Dados de Sequência Molecular , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , RNA Mensageiro/genética , Homologia de Sequência de Aminoácidos , Frações Subcelulares/enzimologiaRESUMO
Genetical genomics, or genetic analysis applied to gene expression data, has not been widely used in plants. We used quantitative cDNA-AFLP to monitor the variation in the expression level of cotton fiber transcripts among a population of inter-specific Gossypium hirsutum × G. barbadense recombinant inbred lines (RILs). Two key fiber developmental stages, elongation (10 days post anthesis, dpa), and secondary cell wall thickening (22 dpa), were studied. Normalized intensity ratios of 3,263 and 1,201 transcript-derived fragments (TDFs) segregating over 88 RILs were analyzed for quantitative trait loci (QTL) mapping for the 10 and 22 dpa fibers, respectively. Two-thirds of all TDFs mapped between 1 and 6 eQTLs (LOD > 3.5). Chromosome 21 had a higher density of eQTLs than other chromosomes in both data sets and, within chromosomes, hotspots of presumably trans-acting eQTLs were identified. The eQTL hotspots were compared to the location of phenotypic QTLs for fiber characteristics among the RILs, and several cases of co-localization were detected. Quantitative RT-PCR for 15 sequenced TDFs showed that 3 TDFs had at least one eQTL at a similar location to those identified by cDNA-AFLP, while 3 other TDFs mapped an eQTL at a similar location but with opposite additive effect. In conclusion, cDNA-AFLP proved to be a cost-effective and highly transferable platform for genome-wide and population-wide gene expression profiling. Because TDFs are anonymous, further validation and interpretation (in silico analysis, qPCR gene profiling) of the eQTL and eQTL hotspots will be facilitated by the increasing availability of cDNA and genomic sequence resources in cotton.
Assuntos
Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , DNA Complementar/genética , Perfilação da Expressão Gênica , Marcadores Genéticos/genética , Genômica , Gossypium/genética , Mapeamento Cromossômico , Cruzamentos Genéticos , DNA de Plantas/genética , Etiquetas de Sequências Expressas , Genes de Plantas , Gossypium/crescimento & desenvolvimento , Análise em Microsséries , Fenótipo , Locos de Características Quantitativas , Reação em Cadeia da Polimerase em Tempo RealRESUMO
The Commonwealth Scientific and Industrial Research Organisation (CSIRO) cotton breeding program is the sole breeding effort for cotton in Australia, developing high performing cultivars for the local industry which is worthâ¼AU$3 billion per annum. The program is supported by Cotton Breeding Australia, a Joint Venture between CSIRO and the program's commercial partner, Cotton Seed Distributors Ltd. (CSD). While the Australian industry is the focus, CSIRO cultivars have global impact in North America, South America, and Europe. The program is unique compared with many other public and commercial breeding programs because it focuses on diverse and integrated research with commercial outcomes. It represents the full research pipeline, supporting extensive long-term fundamental molecular research; native and genetically modified (GM) trait development; germplasm enhancement focused on yield and fiber quality improvements; integration of third-party GM traits; all culminating in the release of new commercial cultivars. This review presents evidence of past breeding successes and outlines current breeding efforts, in the areas of yield and fiber quality improvement, as well as the development of germplasm that is resistant to pests, diseases and abiotic stressors. The success of the program is based on the development of superior germplasm largely through field phenotyping, together with strong commercial partnerships with CSD and Bayer CropScience. These relationships assist in having a shared focus and ensuring commercial impact is maintained, while also providing access to markets, traits, and technology. The historical successes, current foci and future requirements of the CSIRO cotton breeding program have been used to develop a framework designed to augment our breeding system for the future. This will focus on utilizing emerging technologies from the genome to phenome, as well as a panomics approach with data management and integration to develop, test and incorporate new technologies into a breeding program. In addition to streamlining the breeding pipeline for increased genetic gain, this technology will increase the speed of trait and marker identification for use in genome editing, genomic selection and molecular assisted breeding, ultimately producing novel germplasm that will meet the coming challenges of the 21st Century.