Optimización de mapeo de Loci de caracteres cuantitativos asociados a eficiencia de uso de nitrógeno en maíz e identificación de genes candidatos

La absorción de nitrógeno por las plantas tiene un papel importante en su crecimiento. Los fertilizantes nitrogenados son una herramienta útil para aumentar el rendimiento de los cultivos, pero su uso indiscriminado puede causar severos daños ambientales y económicos. Por lo tanto, el mejoramiento para la adaptación a tipos de estrés como la falta de nitrógeno es muy importante. La mayoría de los caracteres más relevantes para el mejoramiento vegetal son cuantitativos. El mapeo de loci de caracteres cuantitativos (QTL) permite identificar regiones del genoma que explican parte de la variación fenotípica observada. El objetivo de este trabajo fue aumentar la precisión de la localización de QTL para eficiencia de uso de nitrógeno (EUN) detectados en los cromosomas 1, 8 y 9 de maíz sobre el mapa genético elaborado a partir de la población de 181 líneas endocriadas recombinantes (RILs) derivada del cruzamiento B100xLP2 incrementando el número de microsatélites o SSR (simple sequence repeats) e INDEL (inserciones-deleciones). En la caracterización genotípica se probaron 149 marcadores moleculares en los parentales, de los cuales 40 fueron usados para evaluar la población de RILs. La incorporación de marcadores nuevos a los mapas de ligamiento permitió una mejor representación de los cromosomas y mayor precisión en la localización de los QTL. El mapeo de QTL se realizó mediante mapeo por intervalo compuesto y se detectaron 11 QTL en los cromosomas 1, 8 y 9. Se identificaron 3155 genes dentro de los intervalos de los QTL detectados y se clasificaron según su función. El 67% de los genes corresponden a proteínas con función putativa. Se identificaron genes relacionados al metabolismo del nitrógeno, respuesta al estrés debido a la falta de nitrógeno en el suelo y transporte de aminoácidosFil: Manzelli, Gisela Andrea. Universidad Nacional del Noroeste de la Provincia de Buenos AiresFil: Mandolino, Cecilia Inés. Universidad Nacional del Noroeste de la Provincia de Buenos Aire

Maize Nitrogen Use Efficiency: QTL Mapping in a U.S. Dent x Argentine-Caribbean Flint RILs population

This study was aimed to identify quantitative trait loci (QTL) for nitrogen use efficiency(NUE) and related traits in a maize population derived from a cross between two lines with different genetic background (B100 and LP2). Recombinant inbred lines (181) from this population were evaluated under fieldconditions during two growing seasons, and significant(P < 0.01) phenotypic and genotypic variability was detected for most evaluated traits. Two different mapping methods were applied for detecting QTLs. Firstly, a trait by trait approach was performed on across environments, and 19 QTLs were identified.Secondly, a multi-trait multi-environment analysis detected seven joint QTLs. Almost all joint QTLs had inconsistent additive effects from one environment to another, which would reflectpresence of QTL × Environment interaction. Most joint QTLs co-localized with QTLs detected by indi-vidual mapping. We detected consistent additive effects for grain yield per plant and NUE, as well as for biomass and nitrogen harvest index in some joint QTLs, especially QTL-1 and QTL-6. These QTLs had positive and stable effects across environments, and presence of some genes within these QTL intervals could be relevant for selecting for both NUE and grain yield simultaneously. Up today, this is a firstreport on the co-localization of QTLs for enhan-ced allocation of biomass allocation to grains with NUE, and NUE candidate gene identificaion. Fine mapping of these regions could allow to detect additional markers more closely linked to these QTLs that could be used for marker assisted selection for NUE

In Silico Identification of MYB and bHLH Families Reveals Candidate Transcription Factors for Secondary Metabolic Pathways in Cannabis sativa L

Plant secondary metabolic pathways are finely regulated by the activity of transcription factors, among which members of the bHLH and MYB subfamilies play a main role. Cannabis sativa L. is a unique officinal plant species with over 600 synthesized phytochemicals having diverse scale-up industrial and pharmaceutical usage. Despite comprehensive knowledge of cannabinoids\u2019 metabolic pathways, very little is known about their regulation, while the literature on flavonoids\u2019 metabolic pathways is still scarce. In this study, we provide the first genome-wide analysis of bHLH and MYB families in C. sativa reference cultivar CBDRx and identification of candidate coding sequences for these transcription factors. Cannabis sativa bHLHs and MYBs were then classified into functional subfamilies through comparative phylogenetic analysis with A. thaliana transcription factors. Analyses of gene structure and motif distribution confirmed that CsbHLHs and CsMYBs belonging to the same evolutionary clade share common features at both gene and amino acidic level. Candidate regulatory genes for key metabolic pathways leading to flavonoid and cannabinoid synthesis in Cannabis were also retrieved. Furthermore, a candidate gene approach was used to identify structural enzyme-coding genes for flavonoid and cannabinoid synthesis. Taken as a whole, this work represents a valuable resource of candidate genes for further investigation of the C. sativa cannabinoid and flavonoid metabolic pathways for genomic studies and breeding programs

Genetic relatedness and population structure within the public Argentinean collection of maize inbred lines

Genetic diversity of an Argentinean public temperate inbred maize collection has not been previously assessed. This collection includes mainly locally developed orange flint germplasm and a group of temperate inbred lines introduced from the US or derived from selection of crosses to genetic stocks from other countries, providing representativeness of exotic gene pools. To establish heterotic groups and patterns for breeding purposes and to assess genetic structure and relatedness for association-mapping studies, a public panel of a 103 maize inbreds was characterized using 50 microsatellite markers and pedigree information. By means of clustering-based and model-based methods the flint germplasm collection was split into two subpopulations that were separated from the BSSS-BS13-related lines. Relatedness estimates with coancestry and kinship coefficients provided additional information in the case of structured mixed membership of some germplasm. These three main subpopulations were in agreement with prior pedigree records. Allele diversity was high and sufficient to give major, minor and specific allele profiles to characterize inbred lines. Convenience of the use of minor allele frequency for structure and relatedness assessment is also discussed. In addition, molecular characterization provided useful information to elucidate inbred ancestry origins of germplasm with unknown pedigree records and to group them into known heterotic groups to define heterotic patterns.Fil: Olmos, Sofí­a Eugenia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Delucchi, Carla. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Ravera, Melina Andrea. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Negri, Maria Emilia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Mandolino, Cecilia Ines. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Eyherabide, Guillermo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino; Argentin

Analysis of sequence variability and transcriptional profile of cannabinoid synthase genes in cannabis sativa l. Chemotypes with a focus on cannabichromenic acid synthase

Cannabis sativa L. has been long cultivated for its narcotic potential due to the accumulation of tetrahydrocannabinolic acid (THCA) in female inflorescences, but nowadays its production for fiber, seeds, edible oil and bioactive compounds has spread throughout the world. However, some hemp varieties still accumulate traces of residual THCA close to the 0.20% limit set by European Union, despite the functional gene encoding for THCA synthase (THCAS) is lacking. Even if some hypotheses have been produced, studies are often in disagreement especially on the role of the cannabichromenic acid synthase (CBCAS). In this work a set of European Cannabis genotypes, representative of all chemotypes, were investigated from a chemical and molecular point of view. Highly specific primer pairs were developed to allow an accurate distinction of different cannabinoid synthases genes. In addition to their use as markers to detect the presence of CBCAS at genomic level, they allowed the analysis of transcriptional profiles in hemp or marijuana plants. While the high level of transcription of THCAS and cannabidiolic acid synthase (CBDAS) clearly reflects the chemical phenotype of the plants, the low but stable transcriptional level of CBCAS in all genotypes suggests that these genes are active and might contribute to the final amount of cannabinoids

Cold storage of liver microorgans in ViaSpan® and BG35 solutions. Study of ammonia metabolism during normothermic reoxygenation

Introduction. This work focuses on ammonia metabolism of Liver Microorgans (LMOs) after cold preservation in a normothermic reoxygenation system (NRS). We have previously reported the development of a novel preservation solution, Bes-Gluconate-PEG 35 kDa (BG35) that showed the same efficacy as ViaSpan® to protect LMOs against cold preservation injury. The objective of this work was to study mRNA levels and activities of two key Urea Cycle enzymes, Carbamyl Phosphate Synthetase I (CPSI) and Ornithine Transcarbamylase (OTC), after preservation of LMOs in BG35 and ViaSpan® and the ability of these tissue slices to detoxify an ammonia overload in a NRS model. Material and methods. After 48 h of cold storage (0°C in BG35 or ViaSpan®) LMOs were rewarmed in KHR containing an ammonium chloride overload (1 mM). We determined ammonium detoxification capacity (ADC), urea synthesis and enzyme activities and relative mRNA levels for CPSI and OTC. Results. At the end of reoxygenation LMOs cold preserved in BG35 have ADC and urea synthesis similar to controls. ViaSpan® group demonstrated a lower capacity to detoxify ammonia and to synthesize urea than fresh LMOs during the whole reoxygenation period which correlated with the lower mRNA levels and activities for CPSI and OTC observed for this group. Conclusion. We demonstrate that our preservation conditions (48 hours, BG35 solution, anoxia, 0oC) did not affect ammonia metabolism of cold preserved LMOs maintaining the physiological and biochemical liver functions tested, which allows their future use as biological component of a BAL system

Kernel weight in maize: genetic control of its physiological and compositional determinants in a dent × flint-caribbean RIL population

The genetic control of maize kernel weight (KW) determination could be studied through its physiological and/ or compositional determinants. Our objective was to dissect the genetic control of maize KW by analyzing its physiological (KGR: kernel growth rate; KFD: kernel filling duration) and compositional (protein, oil, starch) determinants in a dent×flint Caribbean RIL population, which combines a broad genetic background with grains of high added value for industry. An additional objective was to determine the stability of the genetic control under contrasting growing conditions, for which soil nitrogen offer was modified across experiments. Heritability (H2 ) values were high for KW (H2 = 0.74) and intermediate for the other traits (from 0.62 to 0.42). Kernel weight had a strong correlation with KFD (r = 0.69), KGR (r = 0.60) and protein concentration (r = 0.56). Ten joint QTL with inconsistent effects across years and seven epistatic interactions were detected. Despite changes in effect size, most QTL were significant under both environments. Nine QTL were associated with variations in potential KW (KWP), mean KW, KGR and oil concentration, eight with variations in protein and starch concentration and seven with KFD. Epistatic interactions were related to regions with significant main effects. The most important finding was the existence of a common QTL for KWP, KGR and KFD on chromosome 5, for which there was no previous report. Results increased our knowledge on the genetic control of KW through its phenotypic and genetic correlation with KFD, confirming the need to explore different physiological strategies in different genetic backgrounds.Fil: Mandolino, Cecilia Ines. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: D'andrea, Karina Elizabeth. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Producción Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Piedra, Carlina Victoria. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Producción Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Alvarez Prado, Santiago. Institut National de la Recherche Agronomique; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Olmos, Sofia Eugenia. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Cirilo, Alfredo Gabriel. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Otegui, Maria Elena. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Producción Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentin

Kernel weight in maize: genetic control of its physiological and compositional determinants in a dent × flint-caribbean RIL population

The genetic control of maize kernel weight (KW) determination could be studied through its physiological and/ or compositional determinants. Our objective was to dissect the genetic control of maize KW by analyzing its physiological (KGR: kernel growth rate; KFD: kernel filling duration) and compositional (protein, oil, starch) determinants in a dent×flint Caribbean RIL population, which combines a broad genetic background with grains of high added value for industry. An additional objective was to determine the stability of the genetic control under contrasting growing conditions, for which soil nitrogen offer was modified across experiments. Heritability (H2) values were high for KW (H2 = 0.74) and intermediate for the other traits (from 0.62 to 0.42). Kernel weight had a strong correlation with KFD (r = 0.69), KGR (r = 0.60) and protein concentration (r = 0.56). Ten joint QTL with inconsistent effects across years and seven epistatic interactions were detected. Despite changes in effect size, most QTL were significant under both environments. Nine QTL were associated with variations in potential KW (KW ), mean KW, KGR and oil concentration, eight with variations in protein and starch concentration and seven with KFD. Epistatic interactions were related to regions with significant main effects. The most important finding was the existence of a common QTL for KW , KGR and KFD on chromosome 5, for which there was no previous report. Results increased our knowledge on the genetic control of KW through its phenotypic and genetic correlation with KFD, confirming the need to explore different physiological strategies in different genetic backgrounds