Abstract:

Author affiliation: Nani, Juan Pablo. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; Argentina.

La mastitis es considerada la patología que produce mayores pérdidas económicas para la industria láctea en general ya que produce una disminución en la producción, afecta la calidad de la leche, la tasa de preñez, posee altos costos de diagnóstico y tratamiento, y reduce la vida útil del animal en producción. La resistencia a mastitis es un rasgo complejo que depende de componentes genéticos, ambientales y fisiológicos. Las limitaciones de las medidas clásicas de control han llevado a la búsqueda de alternativas para reducir al mínimo el uso de antibióticos, siendo una de ellas la selección de animales naturalmente resistentes. El recuento de células somáticas (RCS) en leche está directamente relacionado con el nivel de inflamación en la ubre. En este trabajo de tesis se usaron dos estrategias: 1) identificar polimorfismos en genes candidatos (seleccionados en base a su función biológica, fisiológica, funcional, o evidencia previa de asociación con la enfermedad) y 2) utilizar un panel de más de 50.000 marcadores de tipo SNP distribuidos uniformemente en el genoma, a fin de identificar regiones cromosómicas asociadas a la variación en el score de células somáticas (SCS), en un estudio de asociación de genoma completo (GWAS, Genome Wide Association Study). Los diferentes análisis se identificaron 8 marcadores significativamente asociados con el SCS. Se confirmó también que el SCS está influenciado por múltiples loci distribuidos por todo el genoma. Estos resultados contribuyen a obtener un mejor conocimiento sobre las regiones genómicas que influyen en el SCS en rodeos lecheros argentinos.

Mastitis is considered to be the pathology that produces the most economic losses for both, the producer and the dairy industry, causing a decrease in production, affecting the quality of milk, the pregnancy rate, and having high costs for diagnosis and treatment as well as reducing the productive life of the animal. Mastitis control programs based on reducing the number of new infections and limiting the duration of existing infections by hygienic practice and using antibiotics has shown mixed efficacy against different pathogens. These limitations promoted the search for alternatives to minimize the use of antibiotics, by stimulating the animal’s defense systems or by selecting animals showing natural resistance to infections. In this thesis two strategies were used: 1) to identify polymorphisms in candidate genes (based on known biological, physiological, or functional relevance to the disease) and 2) use a panel of more than 50,000 SNP markers evenly distributed throughout the bovine genome in order to identify chromosomal regions associated with variation in somatic cell score (SCS) in a Genome Wide Association Study (GWAS). In the association analysis, eight different markers were found significantly associated with the SCS. This analysis confirmed that the SCS is influenced by multiple loci distributed throughout the genome, each contributing a relatively small effect. These results contributed to a better understanding of the genomic regions influencing the SCS in Argentine dairy herds and together with the use of molecular markers may contribute significantly to the design of better selection programs.

Agencia Nacional de Promoción Científica y Tecnológica

Instituto Nacional de Tecnología Agropecuaria

Abstract:

fs8.1 is a major quantitative trait locus (QTL) that controls the elongated shape of tomato (Solanum lycopersicum) fruit. In this study, we fine-mapped the locus from a 47Mb to a 3.03Mb interval on the long arm of chromosome 8. Of the 122 annotated genes found in the fs8.1 region, 51 were expressed during floral development and six were differentially expressed in anthesis-stage ovaries in fs8.1 and wild-type (WT) lines. To identify possible nucleotide polymorphisms that may underlie the fruit shape phenotype, genome sequence analyses between tomato cultivars carrying the mutant and WT allele were conducted. This led to the identification of 158 single-nucleotide polymorphisms (SNPs) and five small indels in the fs8.1 interval, including 31 that could be associated with changes in gene expression or function. Morphological and histological analyses showed that the effects of fs8.1 were mainly on reproductive organ elongation by increasing cell number in the proximal–distal direction. Fruit weight was also increased in fs8.1 compared with WT, which was predominantly attributed to the increased fruit length. By combining the findings from the different analyses, we consider 12 likely candidate genes to underlie fs8.1, including Solyc08g062580 encoding a pentatricopeptide repeat protein, Solyc08g061560 encoding a putative orthologue of ERECTA, which is known to control fruit morphology and inflorescence architecture in Arabidopsis, Solyc08g061910 encoding a GTL2-like trihelix transcription factor, Solyc08g061930 encoding a protein that regulates cytokinin degradation, and two genes, Solyc08g062340 and Solyc08g062450, encoding 17.6kDa class II small heat-shock proteins.

Author affiliation: Sun, Liang. Ohio State University; Estados Unidos

Author affiliation: Rodríguez, Gustavo Rubén. Ohio State University; Estados Unidos. Universidad Nacional de Rosario. Facultad de Cs.agrarias. Departamento de Biologia. Cat.de Genetica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnológico Rosario; Argentina

Author affiliation: Clevenger, Josh P.. Ohio State University; Estados Unidos

Author affiliation: Illa Berenguer, Eudald. Ohio State University; Estados Unidos

Author affiliation: Lin, Jinshan. Ohio State University; Estados Unidos

Author affiliation: Blakeslee, Joshua J.. Ohio State University; Estados Unidos

Author affiliation: Liu, Wenli. Cornell University; Estados Unidos

Author affiliation: Fei, Zhangjun. Cornell University; Estados Unidos

Author affiliation: Wijeratne, Asela. Ohio State University; Estados Unidos

Author affiliation: Meulia, Tea. Ohio State University; Estados Unidos

Author affiliation: Knaap, Esther van der. Ohio State University; Estados Unidos

Abstract:

The genetic diversity of 14 Japanese plum (Prunus salicina Lindl) landraces adapted to an ecosystem of alternating flooding and dry conditions was characterized using neutral simple sequence repeat (SSR) markers. Twelve SSRs located in six chromosomes of the Prunus persica reference genome resulted to be polymorphic, thus allowing identification of all the evaluated landraces. Differentiation between individuals was moderate to high (average shared allele distance (DAS) = 0.64), whereas the genetic diversity was high (average indices polymorphism information content (PIC) = 0.62, observed heterozygosity (Ho) = 0.51, unbiased expected heterozygosity (uHe) = 0.70). Clustering and genetic structure approaches grouped all individuals into two major groups that correlated with flesh color. This finding suggests that the intuitive breeding practices of growers tended to select plum trees according to specific phenotypic traits. These neutral markers were adequate for population genetic studies and cultivar identification. Furthermore, we assessed the SSR flanking genome regions (25 kb) in silico to search for candidate genes related to stress resistance or associated with other agronomic traits of interest. Interestingly, at least 26 of the 118 detected genes seem to be related to fruit quality, plant development, and stress resistance. This study suggests that the molecular characterization of specific landraces of Japanese plum that have been adapted to extreme agroecosystems is a useful approach to localize candidate genes which are potentially interesting for breeding.

Instituto de Biotecnología

Author affiliation: Acuña, Cintia Vanesa. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Rivas, Juan Gabriel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Brambilla, Silvina Maricel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina

Author affiliation: Cerrillo, Teresa. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Delta del Paraná; Argentina

Author affiliation: Frusso, Enrique. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Recursos Biológicos; Argentina

Author affiliation: Garcia, Martin Nahuel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Villalba, Pamela Victoria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Aguirre, Natalia Cristina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Sabio Y Garcia, Julia Verónica. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Martinez, Maria Carolina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Hopp, Horacio Esteban. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Marcucci Poltri, Susana Noemi. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Abstract:

Eucalyptus globulus es la especie forestal con mejor aptitud papelera y para la obtención de bioenergía a partir de celulosa, mayormente plantada en regiones templadas del mundo. Los proyectos genómicos en Eucalyptus han incrementado el número de secuencias disponibles en los bancos de datos públicos. Los marcadores funcionales públicos, si bien son frecuentes en diferentes cultivos, son aún escasos en especies forestales. De allí la importancia de la búsqueda y validación de regiones SSRs en genes de interés, para ser utilizados en futuros proyectos de mejoramiento asistido por marcadores (marker assisted breeding). En este estudio, se identificaron secuencias no redundantes de ADN de Eucalyptus (genómicas y ESTs) depositadas en bancos de datos públicos para revelar secuencias microsatélites y predecir, in silico, su función putativa. Éstas fueron luego validadas en laboratorio para predecir su potencial uso en análisis de diversidad genética. A partir de 12.690 ESTs de Eucalyptus globulus publicados en NCBI se identificaron 4.924 secuencias no redundantes. De éstas, 952 unigenes (19,3%) contenían 1.140 regiones SSR. Luego del análisis bioinformático de estos EST-SSRs, se diseñaron 979 oligonucleótidos novedosos y se predijo su función putativa, incluyendo categorías Gene Ontology (GO) según su proceso biológico, función molecular y componente celular. Se identificaron así 29 SSRs en 24 genes candidatos (estructurales y reguladores) para calidad de madera. Los SSRs se encontraron en promotores, intrones y exones de genes candidatos (GC) de distintas rutas metabólicas (biosíntesis del fenilpropanoico, biosíntesis de celulosa, metabolismo de hemicelulosas, ruta metabólica del shikimato, metabolismo de la metionina y genes de tubulinas y el factor de transcripción LIM1). Un total de 85 SSRs (56 EST-SSRs y 29 SSRs incluídos en GC) hallados en este trabajo fueron analizados para su validación en 8 genotipos de E. globulus, resultando positivos un 65%. A partir de esta validación se obtuvieron 17 EST-SSRs y 12 GC-SSRs polimórficos. Con éstos se estimaron los valores de diversidad en una muestra de 60 individuos no emparentados de E. globulus representantes de seis razas que cubren el rango de distribución natural de la especie. Los valores de PIC, Ho y UHe variaron ampliamente entre aproximadamente 0,02 y 0,9, mientras que el número de alelos varió entre 2 y 16, con un promedio de 7,55. Al realizar el test de Equilibrio de Hardy Weinberg (EHW) para los 29 loci, se encontró que 14 de ellos mostraron un significante déficit de heterocigotas (P<0,01). Este desvío del EHW podría explicarse por la presencia de subestructura poblacional y a la presencia de alelos nulos que sesgó las estimaciones de las frecuencias alélicas. Se realizó el estudio de transferibilidad de 49 loci (37 EST-SSRs validados (polimórficos y monomórficos) y los 12 GC-SSRs polimórficos) a otras seis especies de Eucalyptus (E. camaldulensis, E. dunnii, E. grandis, E. saligna, E. tereticornis y E. viminalis). Se encontró que 33 marcadores amplificaron en las seis especies estudiadas y seis en al menos cinco, mostrando la alta transferiblidad de los mismos. Finalmente, el estudio del polimorfismo y transferibilidad de los marcadores funcionales, permitió la selección de un conjunto de 13 (7 EST-SSRs y 6 GC-SSRs) altamente informativos y transferibles a otras seis especies de Eucalyptus. El conjunto de marcadores desarrollados son altamente informativos tendrán un uso potencial en estudios de diversidad genética, taxonomía, mapeo de QTL y en facilitar, en un futuro, la selección asistida en el mejoramiento de Eucalyptus.

Eucalyptus globulus is the most planted hardwood species for pulpwood in temperate regions. Genomic researches in Eucalyptus have increased the information available in DNA sequence`s public databases. Functional genetic markers, while frequent in crop, are still scarce in forest species. Hence the detection and validation of SSRs in interesting genes to be used in future projects of marker-assisted breeding are needed. Here, Eucalyptus DNA sequences (genomics and ESTs) from public databases were screened to identify non redundant sequences, to discover microsatellite sequences and to in silico predict putative gene functions. These were also validated in wet lab to predict their potential for functional genetic diversity analysis. From 12,690 updated E. globulus EST database published in National Center for Biotechnology Information a total of 4,924 non-redundant sequences were identified. From these ones, 952 unigenes (19.3 %) contained 1,140 SSRs. A new set of 979 primers were designed for putative SSR-markers after bioinformatic analysis. The predicted functions of these EST-SSRs were adjudged, including biological process, molecular function and cellular component Gene Ontology (GO) categories. Twenty four structural and regulatory candidate genes for wood quality carrying 29 SSR were indentified. Microsatellite sequences were located in promoters, introns and exons from candidate genes (CG) from: phenylpropanoid biosynthesis, cellulose biosynthetic process, hemicellulose metabolism, shikimate pathway, methionine metabolism, tubulin genes and the transcriptor factor LIM1. Sixty five percent out of a total of 85 SSR (56 EST-SSRs and 29 SSR containg GC) detected in this work were validated for actual PCR amplification of tree DNA samples in eight genotypes of E. globulus. From this assessment a total of 17 polymorphic EST-SSRs and 12 polymorphic CG-SSRs markers were obtained. These ones were selected for further analyses, so as to accurately estimate genetic information content in a larger sample of 60 non related trees represented major geographical races of the species’ natural distribution. PIC, Ho and UHe values varied over a wide range from around 0.02 to 0.9, whereas the allele number ranged from 2 to 16, with and average of 7.55. Fourteen out of the 29 loci tested showed significant deviation from Hardy Weinberg Equilibrium (HWE) showing a significant deficit of heterozygotes (P <0.01). This deviation from HWE could be explained by the presence of substructure population and the presence of null alleles that biased estimates of allele frequencies. A set of 49 loci (37 validated EST-SSRs (polymorphic and monomorphic) and 12 polymorphic CG-SSRs) were also tested for cross-transferability to other six Eucalyptus species (E. grandis, E. saligna, E. dunnii, E. viminalis, E. camaldulensis, E. tereticornis). A total of 33 out of the 49 validated markers in E. globulus amplified in the six other species and six markers amplified in at least other five. Finally, the analyses of polymorphism and transferability of functional markers, enabled the selection of a set of 13 (7 EST-SSRs and 6 GC-SSRs) highly informative and transferable to other six species of Eucalyptus. The set of highly informative markers developed here will have potential use in studies of genetic diversity, taxonomy, gene mapping and will help the improvement of Eucalyptus trough the assisted selection.

Author affiliation: Acuña, Cintia Vanesa. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Abstract:

Knowledge on the genetic bases of physiological processes determining maize kernel weight (KW) is relevant for maize yield improvement. However, little is known about the genetic control of KW and its component traits: kernel growth rate (KGR) and grain-filling duration (GFD). We phenotyped several grain-filling traits in 245 RILs from the IBM Syn4 population (B73×Mo17) under two environments, and a multi-trait multi-environment quantitative trait loci (QTL) analysis was conducted. We were specifically interested inseeking genetic links of knowncorrelated traits atthe phenotypic level, like kernelmaximum water content(MWC) and KGR. Our specific objectives were (i)to conduct a QTL analysis over grain-filling traits to determine their genetic complexity,(ii)to study the relationships between kernel developmental traits at phenotypic and genetic levels, and (iii) to suggest possible candidate genes for each specific trait using detected QTL and B73 sequence data. All traits showed significant genotype × environment interactions (p < 0.001) and large phenotypic variability. KW variability was positively associated (p < 0.01) with variations in KGR (r = 0.79) and GFD (r = 0.32). As expected, KGR was positively correlated to MWC, while GFD was negatively correlated to the kernel moisture concentration at physiological maturity (MCPM). A total of 10 joint QTL were detected under both environments, located on chromosomes 1, 2, 4, 5, 6, 7, 9 and 10. Most QTL showed inconsistent effects underlying genotype × environment interactions. However, the multi-trait multi-environment approach helped understand genetic correlations between traits, where positive and consistent genetic correlations were observed between KW, KGR and MWC on chromosomes 2, 6, 9 and 10. Only one consistent QTL for KW, GFD and kernel desiccation rate (KDR) was detected. KGR and GFD showed no common consistent QTL, supporting previous observations on independent physiological control. Several detected QTL co-localized with previous mapping studies. With the use of B73 sequence data we described genes within QTL marker intervals, and discussed relevant candidate ones for future dissection. Results showing the co-localization of consistent QTL for KW, KGR and MWC suggest a common genetic basis for these critical secondary traits measured under field conditions.

Author affiliation: Alvarez Prado, Santiago. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; Argentina;

Author affiliation: Lopez, Cesar Gabriel. Universidad Nacional de Lomas de Zamora. Facultad de Ciencias Agrarias; Argentina;

Author affiliation: Gambin, Brenda Laura. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; Argentina; Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Departamento de Biologia. Cátedra de Fisiología Vegetal; Argentina;

Author affiliation: Abertondo, Victor. Advanta Semillas S.A.I.C.;

Author affiliation: Borras, Lucas. Universidad Nacional de Rosario. Facultad de Cs.agrarias; Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Cátedra de Cultivo Extensivos Cereales y Oleaginosas; Argentina;

Abstract:

Argentina tiene una larga tradición en el mejoramiento de girasol, siendo su germoplasma un recurso genético invaluable a nivel mundial. Nuestro país es el tercer exportador mundial de aceite crudo y segundo exportador de harinas proteicas y pellet. Actualmente, la producción del cultivo presenta una importante brecha entre el rendimiento real y el rendimiento potencial debido principalmente a las limitantes generadas por los estreses bióticos y abióticos. El mapeo por asociación (MA) es un método de mapeo de QTL (del inglés, Quantitative trait loci) que tiene el potencial de identificar las bases genéticas de características cuantitativas complejas, alcanzando resolución a nivel de genes individuales. Los objetivos de este trabajo comprendieron: 1) el estudio de la diversidad genómica en colecciones de girasol cultivado conservadas en el Banco Activo de Germoplasma de INTA Manfredi (BAG-IM); y 2) la identificación de genes involucrados en la defensa a la Podredumbre Húmeda del Capítulo (PHC) causada por Sclerotinia sclerotiorum utilizando la estrategia de MA. La población de mapeo por asociación (PMA) para caracteres complejos de INTA, constituida por 137 líneas endocriadas pertenecientes al programa de mejoramiento de girasol, fue genotipificada con un panel de 384 polimorfismos de nucleótido simple (SNPs) basado en la tecnología Veracode (Illumina), 28 genes candidato y 42 marcadores microsatélite (SSRs). Los estudios de diversidad realizados mostraron que tanto los SSR como los SNPs resultaron informativos para la caracterización del germoplasma. En general, las estimas de variabilidad genética fueron moderadas, al tiempo que se obtuvieron evidencias de la existencia de tres grupos genéticos diferentes en la PMA. La respuesta a PHC en las líneas de la PMA fue evaluada a campo durante cinco campañas sucesivas con inoculación asistida con esporas del hongo, registrando como medidas fenotípicas la incidencia, severidad y período de incubación de la enfermedad. El análisis estadístico de las asociaciones fenotipo-genotipo llevado a cabo, ya sea mediante el uso de modelos lineales mixtos que contemplan la existencia de estructuración y relaciones de parentesco entre los individuos de la población de mapeo, o modelos bayesianos de interrogación simultánea de loci, permitió la identificación de polimorfismos asociados con reducción de la enfermedad (p<0,05). Los resultados obtenidos demuestran que los estudios de asociación son herramientas útiles a la hora de identificar genes implicados en caracteres complejos para ser usados como insumos para el mejoramiento genético del cultivo de girasol.

Argentina has a long tradition of sunflower breeding, and its germplasm is a valuable genetic resource worldwide. Our country is the third global oil exporter and the second protein meal pellet exporter. Nowadays, there is a significant gap between actual and potential yield, mainly due to biotic and abiotic stresses. Association mapping (AM) is a method for QTL mapping that has a potential resolution to the level of individual genes. The aims of this thesis were to: a) study the genomic diversity in a set of sunflower accessions preserved at the Active Germplasm bank of INTA Manfredi (AGB-IM); and b) identify gene loci involved in resistance to Sclerotinia Head Rot disease in sunflower by an association mapping approach. The association mapping population (AMP) for complex characters of INTA, composed of 137 inbred lines from the sunflower breeding program, was genotyped with an Illumina 384-plex oligo pool assay, 28 candidate genes and 42 microsatellite markers (SSR). The analysis of polymorphism in the set of sunflower accessions studied here showed that both the microsatellites and Single Nucleotide Polymorphism (SNP) markers were informative for germplasm characterization. In general, the estimates of genetic variability were moderate, while evidence for the existence of three different genetic groups was found in the AMP. The AMP was evaluated for disease incidence, severity and incubation period (PI) after assisted inoculation with the pathogen across five campaigns in replicated field trials. Mixed linear models accounting for population structure and kinship relatedness, as well as a Bayesian approach for multilocus association mapping, were used for the statistical analysis of phenotype-genotype associations, allowing the identification of polymorphisms associated with disease reduction (p<0.05). These results demonstrate the potential of candidate gene association mapping for complex trait dissection in sunflower, contributing to the generation of useful tools for sunflower molecular breeding.

Author affiliation: Filippi, Carla Valeria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Abstract:

Hygienic behavior is an economically beneficial,heritable trait, which has evolved to limit the impact of honeybee pathogens. Selecting and breeding colonies with high levels of hygienic behavior has become a feasible andenvironmentally friendly strategy to control brood diseases in honeybee colonies worldwide. The identification of genes involved in the expression of this character may not only unravel molecular and biochemical pathways underlyinghygienic behavior, but also serve as a practical approach to select disease resistance biomarkers useful for honeybee breeding programs. In the present work, we evaluated, at genetic level, Apis mellifera stocks selected for hygienic behavior, widely used for commercial apiculture in Argentina. We analyzed the expression profiles of five genes previously identified as candidates associated with hygienic behavior both in QTL and global gene expression studies in honeybees, more precisely, involved in perceptionand processing of olfactory information. We validated the differential expression of these genes as potentially responsible for behavioral differences in our selected stocks. Our results indicate that four of them (octopaminereceptor, smell-impaired, odorant-binding protein 3, and odorant-binding protein 4) were differentially expressed between hygienic and non-hygienic bees within our highly hygienic colonies. The present findings improve our understanding of the molecular mechanisms underlying the differentiation of middle-age worker bees in their genetic propensity to perform hygienic behavior. This progresstowards the genetic characterization of highly hygienic colonies that are commercially used in Argentine apiculture lays the groundwork for future development of targets for marker-assisted selection of disease-resistant honeybee stocks

Author affiliation: Scannapieco, Alejandra Carla. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Author affiliation: Mannino, Maria Constanza. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Author affiliation: Soto, Gabriela Cynthia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Author affiliation: Palacio, M. A.. Instituto Nacional de Tecnología Agropecuaria; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina

Author affiliation: Cladera, Jorge Luis. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Author affiliation: Lanzavecchia, Silvia Beatriz. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Abstract:

Understanding the genetic architecture of any quantitative trait requires identifying the genes involved in its expression in different environmental conditions. This goal can be achieved by mutagenesis screens in genetically tractable model organisms such as Drosophila melanogaster. Temperature during ontogenesis is an important environmental factor affecting development and phenotypic variation in holometabolous insects. In spite of the importance of phenotypic plasticity and genotype by environment interaction (GEI) for fitness related traits, its genetic basis has remained elusive. In this context, we analyzed five different adult morphological traits (face width, head width, thorax length, wing size and wing shape) in 42 coisogenic single P-element insertional lines of Drosophila melanogaster raised at 17°C and 25°C. Our analyses showed that all lines differed from the control for at least one trait in males or females at either temperature. However, no line showed those differences for all traits in both sexes and temperatures simultaneously. In this sense, the most pleiotropic candidate genes were CG34460, Lsd-2 and Spn. Our analyses also revealed extensive genetic variation for all the characters mostly indicated by strong GEIs. Further, our results indicate that GEIs were predominantly explained by changes in ranking order in all cases suggesting that a moderate number of genes are involved in the expression of each character at both temperatures. Most lines displayed a plastic response for at least one trait in either sex. In this regard, P-element insertions affecting plasticity of a large number of traits were associated to the candidate genes Btk29A, CG43340, Drak and jim. Further studies will help to elucidate the relevance of these genes on the morphogenesis of different body structures in natural populations of D. melanogaster.

Author affiliation: Carreira, Valeria Paula. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Ecologia, Genetica y Evolucion de Bs. As;

Author affiliation: Imberti, Marcos Agustin. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Ecologia, Genetica y Evolucion de Bs. As;

Author affiliation: Mensch, Julian. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Ecologia, Genetica y Evolucion de Bs. As;

Author affiliation: Fanara, Juan Jose. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Ecologia, Genetica y Evolucion de Bs. As;

Abstract:

Accessory gland proteins (Acps) are part of the seminal fluid of male Drosophila flies. Some Acps have exceptionally high evolutionary rates and evolve under positive selection. Proper interactions between Acps and female reproductive molecules are essential for fertilization. These observations lead to suggestions that fast evolving Acps could be involved in speciation by promoting reproductive incompatibilities between emerging species. To test this hypothesis, we used population genetics data for three sibling species: D. mayaguana, D. parisiena and D. straubae. The latter two species are morphologically very similar and show only incipient reproductive isolation. This system allowed us to examine Acp evolution at different time frames with respect to speciation and reproductive isolation. Comparing data of 14 Acp loci with data obtained for other genomic regions, we found that some Acps show extraordinarily high levels of divergence between D. mayaguana and its two sister species D. parisiena and D. straubae. This divergence was likely driven by adaptive evolution at several loci. No fixed nucleotide differences were found between D. parisiena and D. straubae, however. Nevertheless, some Acp loci did show significant differentiation between these species associated with signs of positive selection; these loci may be involved in this early phase of the speciation process.

Author affiliation: Cunha Almeida, Francisca. University of New York; Estados Unidos. American Museum of Natural History; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Author affiliation: Desalle, R.. American Museum of Natural History; Estados Unidos

Abstract:

In insects, pre-adult stages of the life cycle are exposed to variation in temperature that may differ from that in adults. However, the genetic basis for adaptation to environmental temperature could be similar between the pre-adult and the adult stages of the life cycle. Here, we tested quantitative trait loci (QTL) for heat-stress survival in larvae of Drosophila melanogaster, with and without a mild-heat-stress pre-treatment. Two sets of recombinant inbred lines derived from lines artificially selected for high and low levels of knockdown resistance to high temperature in young flies were used as the mapping population. There was no apparent increase in heat-shock survival between heat-pretreated and non-pretreated larvae. There was a positive correlation between the two experimental conditions of heat-shock survival (with and without a heat pre-treatment) except for males from one set of lines. Several QTL were identified involving all three major chromosomes. Most QTL for larval thermotolerance overlapped with thermotolerance QTL identified in previous studies for adults, indicating that heat-stress resistance is not genetically independent between life cycle stages because of either linkage or pleiotropy. The sign of the effects of some QTL alleles differed both between the sexes and between life stages.

Author affiliation: Sambucetti, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Author affiliation: Scannapieco, Alejandra Carla. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Loeschcke, V.. University Aarhus; Dinamarca

Author affiliation: Norry, Fabian Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina