MELOGEN: an EST database for melon functional genomics

<p>Abstract</p> <p>Background</p> <p>Melon (<it>Cucumis melo </it>L.) is one of the most important fleshy fruits for fresh consumption. Despite this, few genomic resources exist for this species. To facilitate the discovery of genes involved in essential traits, such as fruit development, fruit maturation and disease resistance, and to speed up the process of breeding new and better adapted melon varieties, we have produced a large collection of expressed sequence tags (ESTs) from eight normalized cDNA libraries from different tissues in different physiological conditions.</p> <p>Results</p> <p>We determined over 30,000 ESTs that were clustered into 16,637 non-redundant sequences or unigenes, comprising 6,023 tentative consensus sequences (contigs) and 10,614 unclustered sequences (singletons). Many potential molecular markers were identified in the melon dataset: 1,052 potential simple sequence repeats (SSRs) and 356 single nucleotide polymorphisms (SNPs) were found. Sixty-nine percent of the melon unigenes showed a significant similarity with proteins in databases. Functional classification of the unigenes was carried out following the Gene Ontology scheme. In total, 9,402 unigenes were mapped to one or more ontology. Remarkably, the distributions of melon and Arabidopsis unigenes followed similar tendencies, suggesting that the melon dataset is representative of the whole melon transcriptome. Bioinformatic analyses primarily focused on potential precursors of melon micro RNAs (miRNAs) in the melon dataset, but many other genes potentially controlling disease resistance and fruit quality traits were also identified. Patterns of transcript accumulation were characterised by Real-Time-qPCR for 20 of these genes.</p> <p>Conclusion</p> <p>The collection of ESTs characterised here represents a substantial increase on the genetic information available for melon. A database (MELOGEN) which contains all EST sequences, contig images and several tools for analysis and data mining has been created. This set of sequences constitutes also the basis for an oligo-based microarray for melon that is being used in experiments to further analyse the melon transcriptome.</p

Desarrollo de una plataforma de tilling en melón (Cucumis melo L.)

El trabajo descrito en esta tesis doctoral se enmarca dentro del proyecto MELOGEN (GEN2013‑ 20237, 2004‑2007) uno de cuyos objetivos era la construcción de una plataforma de TILLING en melón. La disponibilidad de recursos genéticos y genómicos para el melón se ha incrementado a lo largo de los últimos años e incluso la secuencia del genoma está disponible. Sin embargo, las herramientas genómicas para determinar la funcionalidad de los genes en esta especie son todavía limitadas. El TILLING (Targeting Induced Local Lesions IN Genomes) es un método de genética inversa mediante el cual se pueden crear e identificar nuevas mutaciones en genes candidatos y observar su efecto fenotípico. Además, también se pueden detectar fenotipos de interés para posteriormente identificar la mutación responsable de los mismos. En este trabajo se ha desarrollado una población de TILLING en Cucumis melo a partir de la línea doble haploide del tipo “Piel de Sapo” M62‑113. Aplicando inicialmente el mutágeno químico EMS (Etil Metano Sulfonato) sobre 17.000 semillas se ha desarrollado una colección de mutantes compuesta por 3.268 familias M2. A partir de 400 familias M2 se observaron diversos fenotipos mutantes en las diferentes etapas de crecimiento de la planta. Algunos de estos mutantes se han descrito con detalle generando un catálogo de los fenotipos observados en cada familia, algunos de los cuales pueden tener interés comercial. Para medir la tasa de mutación de la población se han analizado cuatro genes, la fitoeno desaturasa PDS, los factores de iniciación de la traducción eIF4E y eIF(iso)4E y el receptor de etileno ETR1. Los mutantes detectados han permitido calcular la tasa de mutación de la población, una mutación cada 1,5 Mb. En el caso de PDS se ha podido obtener un mutante con fenotipo albino, demostrando así la efectividad del método TILLING en melón. Además, paralelamente se analizaron los mismos genes en otra población mutagenizada independiente. También se realizó un estudio de EcoTILLING con 113 accesiones de melón y se identificaron 19 haplotipos distintos en el gen eIF4E, uno de ellos, con un SNP que provoca un cambio de aminoácido y que sólo se encuentra en la accesión PI 505602 y dos haplotipos en el gen ETR1, uno de los cuales también contiene un SNP que provoca un cambio de aminoácido. El TILLING facilitará los estudios de genética inversa en melón y abre la puerta a futuros estudios de genómica funcional en un genoma recientemente secuenciado. Este trabajo ha representado también el primer paso para poder desarrollar nuevas poblaciones de TILLING en melón con mayores tasas de mutación y en otros fondos genéticos.The work described in this thesis is part of the MELOGEN project (GEN2013‑20237, 2004‑2007) one of whose goals was to build a melon TILLING platform. The availability of genetic and genomic resources in melon has increased over recent years, and even the sequence of the genome is available. However, genomic tools to determine the functionality of genes in this species are still limited. TILLING (Targeting Induced Local Lesions IN Genomes) is a reverse genetics method by which you can create and identify new mutations in candidate genes and observe their phenotypic effect. Furthermore, it is also possible to detect phenotypes of interest in order to identify their responsible mutation. In this project we developed a TILLING population in Cucumis melo L. in the double haploid M62‑113 line from the ʺPiel de Sapoʺ type. Applying the chemical mutagen EMS (Ethyl methane sulfonate) over 17,000 seeds we have developed a collection of mutants consisting of 3268 M2 families. Phenotypic mutants were observed in 400 M2 families in different stages of plant growth during the development of the population. Some mutant phenotypes have been described and identified in detail by generating a catalogue of phenotypic changes. Some of these phenotypes may have a commercial interest. We have analysed four genes to identify the rate of mutation in the population: Phytoene desaturase (PDS), Eukaryotic translation initiation factors (eIF4E and eIFiso4E) and the Ethylene receptor (ETR1). Mutants detected allowed to calculate the mutation rate of the population, one mutation per 1.5 Mb. For PDS we were able to obtain a mutant with an albino phenotype, demonstrating the effectiveness of TILLING method in melon. Moreover, in parallel the same genes were analyzed in another independent mutagenized population. A study of Ecotilling was also performed in 113 melon accessions and 19 different haplotypes in the eIF4E gene were obtained. One of them contained a SNP that causes an amino acid change and was only found in the accession PI 505602 and two other haplotypes were found in the ETR1 gene, one of which also contains a SNP that causes an amino acid change. TILLING will facilitate reverse genetics studies in melon and opens the possibility of performing future functional genomics studies in a newly sequenced genome. This work has also represented the first step to developing new melon TILLING populations with higher rates of mutation and in other genetic backgrounds

Desarrollo de una plataforma de tilling en melón (Cucumis melo L.)

El trabajo descrito en esta tesis doctoral se enmarca dentro del proyecto MELOGEN (GEN2013‑ 20237, 2004‑2007) uno de cuyos objetivos era la construcción de una plataforma de TILLING en melón. La disponibilidad de recursos genéticos y genómicos para el melón se ha incrementado a lo largo de los últimos años e incluso la secuencia del genoma está disponible. Sin embargo, las herramientas genómicas para determinar la funcionalidad de los genes en esta especie son todavía limitadas. El TILLING (Targeting Induced Local Lesions IN Genomes) es un método de genética inversa mediante el cual se pueden crear e identificar nuevas mutaciones en genes candidatos y observar su efecto fenotípico. Además, también se pueden detectar fenotipos de interés para posteriormente identificar la mutación responsable de los mismos. En este trabajo se ha desarrollado una población de TILLING en Cucumis melo a partir de la línea doble haploide del tipo "Piel de Sapo" M62‑113. Aplicando inicialmente el mutágeno químico EMS (Etil Metano Sulfonato) sobre 17.000 semillas se ha desarrollado una colección de mutantes compuesta por 3.268 familias M2. A partir de 400 familias M2 se observaron diversos fenotipos mutantes en las diferentes etapas de crecimiento de la planta. Algunos de estos mutantes se han descrito con detalle generando un catálogo de los fenotipos observados en cada familia, algunos de los cuales pueden tener interés comercial. Para medir la tasa de mutación de la población se han analizado cuatro genes, la fitoeno desaturasa PDS, los factores de iniciación de la traducción eIF4E y eIF(iso)4E y el receptor de etileno ETR1. Los mutantes detectados han permitido calcular la tasa de mutación de la población, una mutación cada 1,5 Mb. En el caso de PDS se ha podido obtener un mutante con fenotipo albino, demostrando así la efectividad del método TILLING en melón. Además, paralelamente se analizaron los mismos genes en otra población mutagenizada independiente. También se realizó un estudio de EcoTILLING con 113 accesiones de melón y se identificaron 19 haplotipos distintos en el gen eIF4E, uno de ellos, con un SNP que provoca un cambio de aminoácido y que sólo se encuentra en la accesión PI 505602 y dos haplotipos en el gen ETR1, uno de los cuales también contiene un SNP que provoca un cambio de aminoácido. El TILLING facilitará los estudios de genética inversa en melón y abre la puerta a futuros estudios de genómica funcional en un genoma recientemente secuenciado. Este trabajo ha representado también el primer paso para poder desarrollar nuevas poblaciones de TILLING en melón con mayores tasas de mutación y en otros fondos genéticos.The work described in this thesis is part of the MELOGEN project (GEN2013‑20237, 2004‑2007) one of whose goals was to build a melon TILLING platform. The availability of genetic and genomic resources in melon has increased over recent years, and even the sequence of the genome is available. However, genomic tools to determine the functionality of genes in this species are still limited. TILLING (Targeting Induced Local Lesions IN Genomes) is a reverse genetics method by which you can create and identify new mutations in candidate genes and observe their phenotypic effect. Furthermore, it is also possible to detect phenotypes of interest in order to identify their responsible mutation. In this project we developed a TILLING population in Cucumis melo L. in the double haploid M62‑113 line from the ʺPiel de Sapoʺ type. Applying the chemical mutagen EMS (Ethyl methane sulfonate) over 17,000 seeds we have developed a collection of mutants consisting of 3268 M2 families. Phenotypic mutants were observed in 400 M2 families in different stages of plant growth during the development of the population. Some mutant phenotypes have been described and identified in detail by generating a catalogue of phenotypic changes. Some of these phenotypes may have a commercial interest. We have analysed four genes to identify the rate of mutation in the population: Phytoene desaturase (PDS), Eukaryotic translation initiation factors (eIF4E and eIFiso4E) and the Ethylene receptor (ETR1). Mutants detected allowed to calculate the mutation rate of the population, one mutation per 1.5 Mb. For PDS we were able to obtain a mutant with an albino phenotype, demonstrating the effectiveness of TILLING method in melon. Moreover, in parallel the same genes were analyzed in another independent mutagenized population. A study of Ecotilling was also performed in 113 melon accessions and 19 different haplotypes in the eIF4E gene were obtained. One of them contained a SNP that causes an amino acid change and was only found in the accession PI 505602 and two other haplotypes were found in the ETR1 gene, one of which also contains a SNP that causes an amino acid change. TILLING will facilitate reverse genetics studies in melon and opens the possibility of performing future functional genomics studies in a newly sequenced genome. This work has also represented the first step to developing new melon TILLING populations with higher rates of mutation and in other genetic backgrounds

A set of EST-SNPs for map saturation and cultivar identification in melon

<p>Abstract</p> <p>Background</p> <p>There are few genomic tools available in melon (<it>Cucumis melo </it>L.), a member of the <it>Cucurbitaceae</it>, despite its importance as a crop. Among these tools, genetic maps have been constructed mainly using marker types such as simple sequence repeats (SSR), restriction fragment length polymorphisms (RFLP) and amplified fragment length polymorphisms (AFLP) in different mapping populations. There is a growing need for saturating the genetic map with single nucleotide polymorphisms (SNP), more amenable for high throughput analysis, especially if these markers are located in gene coding regions, to provide functional markers. Expressed sequence tags (ESTs) from melon are available in public databases, and resequencing ESTs or validating SNPs detected <it>in silico </it>are excellent ways to discover SNPs.</p> <p>Results</p> <p>EST-based SNPs were discovered after resequencing ESTs between the parental lines of the PI 161375 (SC) × 'Piel de sapo' (PS) genetic map or using <it>in silico </it>SNP information from EST databases. In total 200 EST-based SNPs were mapped in the melon genetic map using a bin-mapping strategy, increasing the map density to 2.35 cM/marker. A subset of 45 SNPs was used to study variation in a panel of 48 melon accessions covering a wide range of the genetic diversity of the species. SNP analysis correctly reflected the genetic relationships compared with other marker systems, being able to distinguish all the accessions and cultivars.</p> <p>Conclusion</p> <p>This is the first example of a genetic map in a cucurbit species that includes a major set of SNP markers discovered using ESTs. The PI 161375 × 'Piel de sapo' melon genetic map has around 700 markers, of which more than 500 are gene-based markers (SNP, RFLP and SSR). This genetic map will be a central tool for the construction of the melon physical map, the step prior to sequencing the complete genome. Using the set of SNP markers, it was possible to define the genetic relationships within a collection of forty-eight melon accessions as efficiently as with SSR markers, and these markers may also be useful for cultivar identification in Occidental melon varieties.</p

Distribution of melon and Arabidopsis unigenes according to the Gene Ontology scheme for functional classification of gene products

<p><b>Copyright information:</b></p><p>Taken from "MELOGEN: an EST database for melon functional genomics"</p><p>http://www.biomedcentral.com/1471-2164/8/306</p><p>BMC Genomics 2007;8():306-306.</p><p>Published online 3 Sep 2007</p><p>PMCID:PMC2034596.</p><p></p