The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jorge Dubcovsky - One of the best experts on this subject based on the ideXlab platform.
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effect of the down regulation of the high Grain Protein content gpc genes on the wheat transcriptome during monocarpic senescence
BMC Genomics, 2011Co-Authors: Dario Cantu, Stephen Pearce, Michael W Christiansen, Eduard Akhunov, Assaf Distelfeld, Cristobal Uauy, Tzion Fahima, Jorge DubcovskyAbstract:Background: Increasing the nutrient concentration of wheat Grains is important to ameliorate nutritional deficiencies in many parts of the world. Proteins and nutrients in the wheat Grain are largely derived from the remobilization of degraded leaf molecules during monocarpic senescence. The down-regulation of the NAC transcription factor Grain Protein Content (GPC) in transgenic wheat plants delays senescence (>3 weeks) and reduces the concentration of Protein, Zn and Fe in the Grain (>30%), linking senescence and nutrient remobilization. Based on the early and rapid up-regulation of GPC in wheat flag leaves after anthesis, we hypothesized that this transcription factor is an early regulator of monocarpic senescence. To test this hypothesis, we used high-throughput mRNA-seq technologies to characterize the effect of the GPC down-regulation on the wheat flag-leaf transcriptome 12 days after anthesis. At this early stage of senescence GPC transcript levels are significantly lower in transgenic GPC-RNAi plants than in the wild type, but there are still no visible phenotypic differences between genotypes. Results: We generated 1.4 million 454 reads from early senescing flag leaves (average ~350 nt) and assembled 1.2 million into 30,497 contigs that were used as a reference to map 145 million Illumina reads from three wild type and four GPC-RNAi plants. Following normalization and statistical testing, we identified a set of 691 genes differentially regulated by GPC (431 ≥ 2-fold change). Transcript level ratios between transgenic and wild type plants showed a high correlation (R = 0.83) between qRT-PCR and Illumina results, providing independent validation of the mRNA-seq approach. A set of differentially expressed genes were analyzed across an early senescence time-course. Conclusions: Monocarpic senescence is an active process characterized by large-scale changes in gene expression which begins considerably before the appearance of visual symptoms of senescence. The mRNA-seq approach used here was able to detect small differences in transcript levels during the early stages of senescence. This resulted in an extensive list of GPC-regulated genes, which includes transporters, hormone regulated genes, and transcription factors. These GPC-regulated genes, particularly those up-regulated during senescence, provide valuable entry points to dissect the early stages of monocarpic senescence and nutrient remobilization in wheat.
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effect of the Grain Protein content locus gpc b1 on bread and pasta quality
Journal of Cereal Science, 2010Co-Authors: Juan Carlos Brevis, Craig F Morris, Frank A Manthey, Jorge DubcovskyAbstract:Grain Protein concentration (GPC) affects wheat nutritional value and several critical parameters for bread and pasta quality. A gene designated Gpc-B1, which is not functional in common and durum wheat cultivars, was recently identified in Triticum turgidum ssp. dicoccoides. The functional allele of Gpc-B1 improves nitrogen remobilization from the straw increasing GPC, but also shortens the Grain filling period resulting in reduced Grain weight in some genetic backgrounds. We developed isogenic lines for the Gpc-B1 introgression in six hexaploid and two tetraploid wheat genotypes to evaluate its effects on bread-making and pasta quality. In common wheat, the functional Gpc-B1 introgression was associated with significantly higher GPC, water absorption, mixing time and loaf volume, whereas in durum wheat, the introgression resulted in significant increases in GPC, wet gluten, mixing time, and spaghetti firmness, as well as a decrease in cooking loss. On the negative side, the functional Gpc-B1 introgression was associated in some varieties with a significant reduction in Grain weight, test weight, and flour yield and significant increases in ash concentration. Significant gene × environment and gene × genotype interactions for most traits stress the need for evaluating the effect of this introgression in particular genotypes and environments.
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Colinearity between the barley Grain Protein content (GPC) QTL on chromosome arm 6HS and the wheat Gpc-B1 region
Molecular Breeding, 2008Co-Authors: Assaf Distelfeld, Cristobal Uauy, Jorge Dubcovsky, Abraham B. Korol, Tom Blake, Tzion FahimaAbstract:Grain Protein Content (GPC) is an important determinant of Grain quality in many crops, including barley and wheat. Recently, the map-based cloning of Gpc-B1, a wheat GPC quantitative trait locus (QTL), revealed a NAC transcription factor (TtNAM-B1) that was associated with increased Grain Protein, zinc, and iron content. In barley, a QTL for GPC was identified in a segregating population developed from a cross between ‘Karl’ (low GPC) and ‘Lewis’ (average GPC). This QTL was mapped near marker hvm74 on chromosome 6H and was suggested as a potential orthologue for Gpc-B1 on chromosome arm 6BS. In the current study, wheat genes that were previously mapped within a 0.8 cM segment spanning the TtNAM-B1 gene were converted into barley molecular markers. These new markers, together with the barley TtNAM-B1 orthologous gene (designated HvNAM-1 hereafter) were mapped on a 0.7 cM interval encompassing the peak of the barley QTL for GPC on chromosome arm 6HS. Sequence comparison of HvNAM-1 parental alleles showed two single nucleotide polymorphisms (SNPs) that result in two amino acid differences. Analysis of the allelic variation in a wild and cultivated barley collection revealed that the Karl haplotype was present only in nine out of 147 tested accessions. The colinearity between the wheat and barley GPC regions and the low frequency of the HvNAM-1 haplotype associated with low GPC suggest that the barley NAC transcription factor is responsible for the GPC QTL on barley chromosome 6H.
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a nac gene regulating senescence improves Grain Protein zinc and iron content in wheat
Science, 2006Co-Authors: Cristobal Uauy, Assaf Distelfeld, Tzion Fahima, Ann E Blechl, Jorge DubcovskyAbstract:Enhancing the nutritional value of food crops is a means of improving human nutrition and health. We report here the positional cloning of Gpc-B1, a wheat quantitative trait locus associated with increased Grain Protein, zinc, and iron content. The ancestral wild wheat allele encodes a NAC transcription factor (NAM-B1) that accelerates senescence and increases nutrient remobilization from leaves to developing Grains, whereas modern wheat varieties carry a nonfunctional NAM-B1 allele. Reduction in RNA levels of the multiple NAM homologs by RNA interference delayed senescence by more than 3 weeks and reduced wheat Grain Protein, zinc, and iron content by more than 30%.
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the high Grain Protein content gene gpc b1 accelerates senescence and has pleiotropic effects on Protein content in wheat
Journal of Experimental Botany, 2006Co-Authors: Cristobal Uauy, Juan Carlos Brevis, Jorge DubcovskyAbstract:High Grain Protein content (GPC) is a frequent target of wheat breeding programmes because of its positive effect on bread and pasta quality. A wild wheat allele at the Gpc-B1 locus with a significant impact on this trait was identified previously. The precise mapping of several senescence-related traits in a set of tetraploid recombinant substitution lines (RSLs) segregating for Gpc-B1 is reported here. Flag leaf chlorophyll degradation, change in peduncle colour, and spike water content were completely linked to the Gpc-B1 locus and to the differences in GPC within a 0.3 cM interval corresponding to a physical distance of only 250 kb. The effect of Gpc-B1 was also examined in different environments and genetic backgrounds using a set of tetraploid and hexaploid pairs of isogenic lines. The results were consistent with those observed in the RSLs. The high GPC allele conferred a shorter duration of Grain fill due to earlier flag leaf senescence and increased GPC in all four genetic backgrounds. The effect on Grain size was more variable, depending on the genotype-environment combinations. These results are consistent with a model in which the wild-type allele of Gpc-B1 accelerates senescence in flag leaves producing pleiotropic effects on nitrogen remobilization, total GPC, and Grain size.
Assaf Distelfeld - One of the best experts on this subject based on the ideXlab platform.
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effect of the down regulation of the high Grain Protein content gpc genes on the wheat transcriptome during monocarpic senescence
BMC Genomics, 2011Co-Authors: Dario Cantu, Stephen Pearce, Michael W Christiansen, Eduard Akhunov, Assaf Distelfeld, Cristobal Uauy, Tzion Fahima, Jorge DubcovskyAbstract:Background: Increasing the nutrient concentration of wheat Grains is important to ameliorate nutritional deficiencies in many parts of the world. Proteins and nutrients in the wheat Grain are largely derived from the remobilization of degraded leaf molecules during monocarpic senescence. The down-regulation of the NAC transcription factor Grain Protein Content (GPC) in transgenic wheat plants delays senescence (>3 weeks) and reduces the concentration of Protein, Zn and Fe in the Grain (>30%), linking senescence and nutrient remobilization. Based on the early and rapid up-regulation of GPC in wheat flag leaves after anthesis, we hypothesized that this transcription factor is an early regulator of monocarpic senescence. To test this hypothesis, we used high-throughput mRNA-seq technologies to characterize the effect of the GPC down-regulation on the wheat flag-leaf transcriptome 12 days after anthesis. At this early stage of senescence GPC transcript levels are significantly lower in transgenic GPC-RNAi plants than in the wild type, but there are still no visible phenotypic differences between genotypes. Results: We generated 1.4 million 454 reads from early senescing flag leaves (average ~350 nt) and assembled 1.2 million into 30,497 contigs that were used as a reference to map 145 million Illumina reads from three wild type and four GPC-RNAi plants. Following normalization and statistical testing, we identified a set of 691 genes differentially regulated by GPC (431 ≥ 2-fold change). Transcript level ratios between transgenic and wild type plants showed a high correlation (R = 0.83) between qRT-PCR and Illumina results, providing independent validation of the mRNA-seq approach. A set of differentially expressed genes were analyzed across an early senescence time-course. Conclusions: Monocarpic senescence is an active process characterized by large-scale changes in gene expression which begins considerably before the appearance of visual symptoms of senescence. The mRNA-seq approach used here was able to detect small differences in transcript levels during the early stages of senescence. This resulted in an extensive list of GPC-regulated genes, which includes transporters, hormone regulated genes, and transcription factors. These GPC-regulated genes, particularly those up-regulated during senescence, provide valuable entry points to dissect the early stages of monocarpic senescence and nutrient remobilization in wheat.
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Colinearity between the barley Grain Protein content (GPC) QTL on chromosome arm 6HS and the wheat Gpc-B1 region
Molecular Breeding, 2008Co-Authors: Assaf Distelfeld, Cristobal Uauy, Jorge Dubcovsky, Abraham B. Korol, Tom Blake, Tzion FahimaAbstract:Grain Protein Content (GPC) is an important determinant of Grain quality in many crops, including barley and wheat. Recently, the map-based cloning of Gpc-B1, a wheat GPC quantitative trait locus (QTL), revealed a NAC transcription factor (TtNAM-B1) that was associated with increased Grain Protein, zinc, and iron content. In barley, a QTL for GPC was identified in a segregating population developed from a cross between ‘Karl’ (low GPC) and ‘Lewis’ (average GPC). This QTL was mapped near marker hvm74 on chromosome 6H and was suggested as a potential orthologue for Gpc-B1 on chromosome arm 6BS. In the current study, wheat genes that were previously mapped within a 0.8 cM segment spanning the TtNAM-B1 gene were converted into barley molecular markers. These new markers, together with the barley TtNAM-B1 orthologous gene (designated HvNAM-1 hereafter) were mapped on a 0.7 cM interval encompassing the peak of the barley QTL for GPC on chromosome arm 6HS. Sequence comparison of HvNAM-1 parental alleles showed two single nucleotide polymorphisms (SNPs) that result in two amino acid differences. Analysis of the allelic variation in a wild and cultivated barley collection revealed that the Karl haplotype was present only in nine out of 147 tested accessions. The colinearity between the wheat and barley GPC regions and the low frequency of the HvNAM-1 haplotype associated with low GPC suggest that the barley NAC transcription factor is responsible for the GPC QTL on barley chromosome 6H.
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multiple qtl effects of wheat gpc b1 locus on Grain Protein and micronutrient concentrations
Physiologia Plantarum, 2007Co-Authors: Assaf Distelfeld, Ismail Cakmak, Zvi Peleg, Levent Ozturk, Atilla Yazici, Hikmet Budak, Yehoshua Saranga, Tzion FahimaAbstract:Micronutrient malnutrition afflicts over three bill ion people worldwide and the numbers are continuously increasing. Developing genetically micronutrient-enriched cereals, which are the predominant source of human dietary, is essential to alleviate malnutrition worldwide. Wheat chromosome 6B derived from wild emmer wheat [Triticum turgidum ssp. dicoccoides (Korn.) Thell] was previously reported to be associated with high Zn concentration in the Grain. In the present study, recombinant chromosome substitution lines (RSLs), previously constructed for genetic and physical maps of Gpc-B1 (a 250-kb locus affecting Grain Protein concentration), were used to identify the effects of the Gpc-B1 locus on Grain micronutrient concentrations. RSLs carrying the Gpc-B 1 allele of T. dicoccoides accumulated on average 12% higher concentration of Zn, 18% higher concentration of Fe, 29% higher concentration of Mn and 38% higher concentration of Protein in the Grain as compared with RSLs carrying the allele from cultivated wheat (Triticum durum). Furthermore, the high Grain Zn, Fe and Mn concentrations were consistently expressed in five different environments with an absence of genotype by environment interaction. The results obtained in the present study also confirmed the previously reported effect of the wild-type allele of Gpc-B1 on earlier senescence of flag leaves. We suggest that the Gpc-B1 locus is involved in more efficient remobilization of Protein, zinc, iron and manganese from leaves to the Grains, in addition to its effect on earlier senescence of the green tissues.
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a nac gene regulating senescence improves Grain Protein zinc and iron content in wheat
Science, 2006Co-Authors: Cristobal Uauy, Assaf Distelfeld, Tzion Fahima, Ann E Blechl, Jorge DubcovskyAbstract:Enhancing the nutritional value of food crops is a means of improving human nutrition and health. We report here the positional cloning of Gpc-B1, a wheat quantitative trait locus associated with increased Grain Protein, zinc, and iron content. The ancestral wild wheat allele encodes a NAC transcription factor (NAM-B1) that accelerates senescence and increases nutrient remobilization from leaves to developing Grains, whereas modern wheat varieties carry a nonfunctional NAM-B1 allele. Reduction in RNA levels of the multiple NAM homologs by RNA interference delayed senescence by more than 3 weeks and reduced wheat Grain Protein, zinc, and iron content by more than 30%.
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physical map of the wheat high Grain Protein content gene gpc b1 and development of a high throughput molecular marker
New Phytologist, 2006Co-Authors: Assaf Distelfeld, Cristobal Uauy, Tzion Fahima, Jorge DubcovskyAbstract:Grain Protein content (GPC) is important for human nutrition and has a strong influence on pasta and bread quality. A quantitative trait locus, derived from a Triticum turgidum ssp. dicoccoides accession (DIC), with an average increase in GPC of 14 g kg(-1) was mapped on chromosome 6BS. Using the wheat-rice colinearity, a high-density map of the wheat region was developed and the quantitative trait locus was mapped as a simple Mendelian locus designated Gpc-B1. A physical map of approx. 250 kb of the Gpc-B1 region was developed using a tetraploid wheat bacterial artificial chromosome library. The constructed physical map included the two Gpc-B1 flanking markers and one potential candidate gene from the colinear rice region completely linked to Gpc-B1. The relationship between physical and genetic distances and the feasibility of isolating genes by positional cloning in wheat are discussed. A high-throughput codominant marker, Xuhw89, was developed. A 4-bp deletion present in the DIC allele was absent in a collection of 117 cultivated tetraploid and hexaploid wheat germplasm, suggesting that this marker will be useful to incorporate the high GPC allele from the DIC accession studied here into commercial wheat varieties.
Tzion Fahima - One of the best experts on this subject based on the ideXlab platform.
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effect of the down regulation of the high Grain Protein content gpc genes on the wheat transcriptome during monocarpic senescence
BMC Genomics, 2011Co-Authors: Dario Cantu, Stephen Pearce, Michael W Christiansen, Eduard Akhunov, Assaf Distelfeld, Cristobal Uauy, Tzion Fahima, Jorge DubcovskyAbstract:Background: Increasing the nutrient concentration of wheat Grains is important to ameliorate nutritional deficiencies in many parts of the world. Proteins and nutrients in the wheat Grain are largely derived from the remobilization of degraded leaf molecules during monocarpic senescence. The down-regulation of the NAC transcription factor Grain Protein Content (GPC) in transgenic wheat plants delays senescence (>3 weeks) and reduces the concentration of Protein, Zn and Fe in the Grain (>30%), linking senescence and nutrient remobilization. Based on the early and rapid up-regulation of GPC in wheat flag leaves after anthesis, we hypothesized that this transcription factor is an early regulator of monocarpic senescence. To test this hypothesis, we used high-throughput mRNA-seq technologies to characterize the effect of the GPC down-regulation on the wheat flag-leaf transcriptome 12 days after anthesis. At this early stage of senescence GPC transcript levels are significantly lower in transgenic GPC-RNAi plants than in the wild type, but there are still no visible phenotypic differences between genotypes. Results: We generated 1.4 million 454 reads from early senescing flag leaves (average ~350 nt) and assembled 1.2 million into 30,497 contigs that were used as a reference to map 145 million Illumina reads from three wild type and four GPC-RNAi plants. Following normalization and statistical testing, we identified a set of 691 genes differentially regulated by GPC (431 ≥ 2-fold change). Transcript level ratios between transgenic and wild type plants showed a high correlation (R = 0.83) between qRT-PCR and Illumina results, providing independent validation of the mRNA-seq approach. A set of differentially expressed genes were analyzed across an early senescence time-course. Conclusions: Monocarpic senescence is an active process characterized by large-scale changes in gene expression which begins considerably before the appearance of visual symptoms of senescence. The mRNA-seq approach used here was able to detect small differences in transcript levels during the early stages of senescence. This resulted in an extensive list of GPC-regulated genes, which includes transporters, hormone regulated genes, and transcription factors. These GPC-regulated genes, particularly those up-regulated during senescence, provide valuable entry points to dissect the early stages of monocarpic senescence and nutrient remobilization in wheat.
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Colinearity between the barley Grain Protein content (GPC) QTL on chromosome arm 6HS and the wheat Gpc-B1 region
Molecular Breeding, 2008Co-Authors: Assaf Distelfeld, Cristobal Uauy, Jorge Dubcovsky, Abraham B. Korol, Tom Blake, Tzion FahimaAbstract:Grain Protein Content (GPC) is an important determinant of Grain quality in many crops, including barley and wheat. Recently, the map-based cloning of Gpc-B1, a wheat GPC quantitative trait locus (QTL), revealed a NAC transcription factor (TtNAM-B1) that was associated with increased Grain Protein, zinc, and iron content. In barley, a QTL for GPC was identified in a segregating population developed from a cross between ‘Karl’ (low GPC) and ‘Lewis’ (average GPC). This QTL was mapped near marker hvm74 on chromosome 6H and was suggested as a potential orthologue for Gpc-B1 on chromosome arm 6BS. In the current study, wheat genes that were previously mapped within a 0.8 cM segment spanning the TtNAM-B1 gene were converted into barley molecular markers. These new markers, together with the barley TtNAM-B1 orthologous gene (designated HvNAM-1 hereafter) were mapped on a 0.7 cM interval encompassing the peak of the barley QTL for GPC on chromosome arm 6HS. Sequence comparison of HvNAM-1 parental alleles showed two single nucleotide polymorphisms (SNPs) that result in two amino acid differences. Analysis of the allelic variation in a wild and cultivated barley collection revealed that the Karl haplotype was present only in nine out of 147 tested accessions. The colinearity between the wheat and barley GPC regions and the low frequency of the HvNAM-1 haplotype associated with low GPC suggest that the barley NAC transcription factor is responsible for the GPC QTL on barley chromosome 6H.
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multiple qtl effects of wheat gpc b1 locus on Grain Protein and micronutrient concentrations
Physiologia Plantarum, 2007Co-Authors: Assaf Distelfeld, Ismail Cakmak, Zvi Peleg, Levent Ozturk, Atilla Yazici, Hikmet Budak, Yehoshua Saranga, Tzion FahimaAbstract:Micronutrient malnutrition afflicts over three bill ion people worldwide and the numbers are continuously increasing. Developing genetically micronutrient-enriched cereals, which are the predominant source of human dietary, is essential to alleviate malnutrition worldwide. Wheat chromosome 6B derived from wild emmer wheat [Triticum turgidum ssp. dicoccoides (Korn.) Thell] was previously reported to be associated with high Zn concentration in the Grain. In the present study, recombinant chromosome substitution lines (RSLs), previously constructed for genetic and physical maps of Gpc-B1 (a 250-kb locus affecting Grain Protein concentration), were used to identify the effects of the Gpc-B1 locus on Grain micronutrient concentrations. RSLs carrying the Gpc-B 1 allele of T. dicoccoides accumulated on average 12% higher concentration of Zn, 18% higher concentration of Fe, 29% higher concentration of Mn and 38% higher concentration of Protein in the Grain as compared with RSLs carrying the allele from cultivated wheat (Triticum durum). Furthermore, the high Grain Zn, Fe and Mn concentrations were consistently expressed in five different environments with an absence of genotype by environment interaction. The results obtained in the present study also confirmed the previously reported effect of the wild-type allele of Gpc-B1 on earlier senescence of flag leaves. We suggest that the Gpc-B1 locus is involved in more efficient remobilization of Protein, zinc, iron and manganese from leaves to the Grains, in addition to its effect on earlier senescence of the green tissues.
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a nac gene regulating senescence improves Grain Protein zinc and iron content in wheat
Science, 2006Co-Authors: Cristobal Uauy, Assaf Distelfeld, Tzion Fahima, Ann E Blechl, Jorge DubcovskyAbstract:Enhancing the nutritional value of food crops is a means of improving human nutrition and health. We report here the positional cloning of Gpc-B1, a wheat quantitative trait locus associated with increased Grain Protein, zinc, and iron content. The ancestral wild wheat allele encodes a NAC transcription factor (NAM-B1) that accelerates senescence and increases nutrient remobilization from leaves to developing Grains, whereas modern wheat varieties carry a nonfunctional NAM-B1 allele. Reduction in RNA levels of the multiple NAM homologs by RNA interference delayed senescence by more than 3 weeks and reduced wheat Grain Protein, zinc, and iron content by more than 30%.
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physical map of the wheat high Grain Protein content gene gpc b1 and development of a high throughput molecular marker
New Phytologist, 2006Co-Authors: Assaf Distelfeld, Cristobal Uauy, Tzion Fahima, Jorge DubcovskyAbstract:Grain Protein content (GPC) is important for human nutrition and has a strong influence on pasta and bread quality. A quantitative trait locus, derived from a Triticum turgidum ssp. dicoccoides accession (DIC), with an average increase in GPC of 14 g kg(-1) was mapped on chromosome 6BS. Using the wheat-rice colinearity, a high-density map of the wheat region was developed and the quantitative trait locus was mapped as a simple Mendelian locus designated Gpc-B1. A physical map of approx. 250 kb of the Gpc-B1 region was developed using a tetraploid wheat bacterial artificial chromosome library. The constructed physical map included the two Gpc-B1 flanking markers and one potential candidate gene from the colinear rice region completely linked to Gpc-B1. The relationship between physical and genetic distances and the feasibility of isolating genes by positional cloning in wheat are discussed. A high-throughput codominant marker, Xuhw89, was developed. A 4-bp deletion present in the DIC allele was absent in a collection of 117 cultivated tetraploid and hexaploid wheat germplasm, suggesting that this marker will be useful to incorporate the high GPC allele from the DIC accession studied here into commercial wheat varieties.
Cristobal Uauy - One of the best experts on this subject based on the ideXlab platform.
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effect of the down regulation of the high Grain Protein content gpc genes on the wheat transcriptome during monocarpic senescence
BMC Genomics, 2011Co-Authors: Dario Cantu, Stephen Pearce, Michael W Christiansen, Eduard Akhunov, Assaf Distelfeld, Cristobal Uauy, Tzion Fahima, Jorge DubcovskyAbstract:Background: Increasing the nutrient concentration of wheat Grains is important to ameliorate nutritional deficiencies in many parts of the world. Proteins and nutrients in the wheat Grain are largely derived from the remobilization of degraded leaf molecules during monocarpic senescence. The down-regulation of the NAC transcription factor Grain Protein Content (GPC) in transgenic wheat plants delays senescence (>3 weeks) and reduces the concentration of Protein, Zn and Fe in the Grain (>30%), linking senescence and nutrient remobilization. Based on the early and rapid up-regulation of GPC in wheat flag leaves after anthesis, we hypothesized that this transcription factor is an early regulator of monocarpic senescence. To test this hypothesis, we used high-throughput mRNA-seq technologies to characterize the effect of the GPC down-regulation on the wheat flag-leaf transcriptome 12 days after anthesis. At this early stage of senescence GPC transcript levels are significantly lower in transgenic GPC-RNAi plants than in the wild type, but there are still no visible phenotypic differences between genotypes. Results: We generated 1.4 million 454 reads from early senescing flag leaves (average ~350 nt) and assembled 1.2 million into 30,497 contigs that were used as a reference to map 145 million Illumina reads from three wild type and four GPC-RNAi plants. Following normalization and statistical testing, we identified a set of 691 genes differentially regulated by GPC (431 ≥ 2-fold change). Transcript level ratios between transgenic and wild type plants showed a high correlation (R = 0.83) between qRT-PCR and Illumina results, providing independent validation of the mRNA-seq approach. A set of differentially expressed genes were analyzed across an early senescence time-course. Conclusions: Monocarpic senescence is an active process characterized by large-scale changes in gene expression which begins considerably before the appearance of visual symptoms of senescence. The mRNA-seq approach used here was able to detect small differences in transcript levels during the early stages of senescence. This resulted in an extensive list of GPC-regulated genes, which includes transporters, hormone regulated genes, and transcription factors. These GPC-regulated genes, particularly those up-regulated during senescence, provide valuable entry points to dissect the early stages of monocarpic senescence and nutrient remobilization in wheat.
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Colinearity between the barley Grain Protein content (GPC) QTL on chromosome arm 6HS and the wheat Gpc-B1 region
Molecular Breeding, 2008Co-Authors: Assaf Distelfeld, Cristobal Uauy, Jorge Dubcovsky, Abraham B. Korol, Tom Blake, Tzion FahimaAbstract:Grain Protein Content (GPC) is an important determinant of Grain quality in many crops, including barley and wheat. Recently, the map-based cloning of Gpc-B1, a wheat GPC quantitative trait locus (QTL), revealed a NAC transcription factor (TtNAM-B1) that was associated with increased Grain Protein, zinc, and iron content. In barley, a QTL for GPC was identified in a segregating population developed from a cross between ‘Karl’ (low GPC) and ‘Lewis’ (average GPC). This QTL was mapped near marker hvm74 on chromosome 6H and was suggested as a potential orthologue for Gpc-B1 on chromosome arm 6BS. In the current study, wheat genes that were previously mapped within a 0.8 cM segment spanning the TtNAM-B1 gene were converted into barley molecular markers. These new markers, together with the barley TtNAM-B1 orthologous gene (designated HvNAM-1 hereafter) were mapped on a 0.7 cM interval encompassing the peak of the barley QTL for GPC on chromosome arm 6HS. Sequence comparison of HvNAM-1 parental alleles showed two single nucleotide polymorphisms (SNPs) that result in two amino acid differences. Analysis of the allelic variation in a wild and cultivated barley collection revealed that the Karl haplotype was present only in nine out of 147 tested accessions. The colinearity between the wheat and barley GPC regions and the low frequency of the HvNAM-1 haplotype associated with low GPC suggest that the barley NAC transcription factor is responsible for the GPC QTL on barley chromosome 6H.
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a nac gene regulating senescence improves Grain Protein zinc and iron content in wheat
Science, 2006Co-Authors: Cristobal Uauy, Assaf Distelfeld, Tzion Fahima, Ann E Blechl, Jorge DubcovskyAbstract:Enhancing the nutritional value of food crops is a means of improving human nutrition and health. We report here the positional cloning of Gpc-B1, a wheat quantitative trait locus associated with increased Grain Protein, zinc, and iron content. The ancestral wild wheat allele encodes a NAC transcription factor (NAM-B1) that accelerates senescence and increases nutrient remobilization from leaves to developing Grains, whereas modern wheat varieties carry a nonfunctional NAM-B1 allele. Reduction in RNA levels of the multiple NAM homologs by RNA interference delayed senescence by more than 3 weeks and reduced wheat Grain Protein, zinc, and iron content by more than 30%.
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the high Grain Protein content gene gpc b1 accelerates senescence and has pleiotropic effects on Protein content in wheat
Journal of Experimental Botany, 2006Co-Authors: Cristobal Uauy, Juan Carlos Brevis, Jorge DubcovskyAbstract:High Grain Protein content (GPC) is a frequent target of wheat breeding programmes because of its positive effect on bread and pasta quality. A wild wheat allele at the Gpc-B1 locus with a significant impact on this trait was identified previously. The precise mapping of several senescence-related traits in a set of tetraploid recombinant substitution lines (RSLs) segregating for Gpc-B1 is reported here. Flag leaf chlorophyll degradation, change in peduncle colour, and spike water content were completely linked to the Gpc-B1 locus and to the differences in GPC within a 0.3 cM interval corresponding to a physical distance of only 250 kb. The effect of Gpc-B1 was also examined in different environments and genetic backgrounds using a set of tetraploid and hexaploid pairs of isogenic lines. The results were consistent with those observed in the RSLs. The high GPC allele conferred a shorter duration of Grain fill due to earlier flag leaf senescence and increased GPC in all four genetic backgrounds. The effect on Grain size was more variable, depending on the genotype-environment combinations. These results are consistent with a model in which the wild-type allele of Gpc-B1 accelerates senescence in flag leaves producing pleiotropic effects on nitrogen remobilization, total GPC, and Grain size.
-
physical map of the wheat high Grain Protein content gene gpc b1 and development of a high throughput molecular marker
New Phytologist, 2006Co-Authors: Assaf Distelfeld, Cristobal Uauy, Tzion Fahima, Jorge DubcovskyAbstract:Grain Protein content (GPC) is important for human nutrition and has a strong influence on pasta and bread quality. A quantitative trait locus, derived from a Triticum turgidum ssp. dicoccoides accession (DIC), with an average increase in GPC of 14 g kg(-1) was mapped on chromosome 6BS. Using the wheat-rice colinearity, a high-density map of the wheat region was developed and the quantitative trait locus was mapped as a simple Mendelian locus designated Gpc-B1. A physical map of approx. 250 kb of the Gpc-B1 region was developed using a tetraploid wheat bacterial artificial chromosome library. The constructed physical map included the two Gpc-B1 flanking markers and one potential candidate gene from the colinear rice region completely linked to Gpc-B1. The relationship between physical and genetic distances and the feasibility of isolating genes by positional cloning in wheat are discussed. A high-throughput codominant marker, Xuhw89, was developed. A 4-bp deletion present in the DIC allele was absent in a collection of 117 cultivated tetraploid and hexaploid wheat germplasm, suggesting that this marker will be useful to incorporate the high GPC allele from the DIC accession studied here into commercial wheat varieties.
Juan Carlos Brevis - One of the best experts on this subject based on the ideXlab platform.
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effect of the Grain Protein content locus gpc b1 on bread and pasta quality
Journal of Cereal Science, 2010Co-Authors: Juan Carlos Brevis, Craig F Morris, Frank A Manthey, Jorge DubcovskyAbstract:Grain Protein concentration (GPC) affects wheat nutritional value and several critical parameters for bread and pasta quality. A gene designated Gpc-B1, which is not functional in common and durum wheat cultivars, was recently identified in Triticum turgidum ssp. dicoccoides. The functional allele of Gpc-B1 improves nitrogen remobilization from the straw increasing GPC, but also shortens the Grain filling period resulting in reduced Grain weight in some genetic backgrounds. We developed isogenic lines for the Gpc-B1 introgression in six hexaploid and two tetraploid wheat genotypes to evaluate its effects on bread-making and pasta quality. In common wheat, the functional Gpc-B1 introgression was associated with significantly higher GPC, water absorption, mixing time and loaf volume, whereas in durum wheat, the introgression resulted in significant increases in GPC, wet gluten, mixing time, and spaghetti firmness, as well as a decrease in cooking loss. On the negative side, the functional Gpc-B1 introgression was associated in some varieties with a significant reduction in Grain weight, test weight, and flour yield and significant increases in ash concentration. Significant gene × environment and gene × genotype interactions for most traits stress the need for evaluating the effect of this introgression in particular genotypes and environments.
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the high Grain Protein content gene gpc b1 accelerates senescence and has pleiotropic effects on Protein content in wheat
Journal of Experimental Botany, 2006Co-Authors: Cristobal Uauy, Juan Carlos Brevis, Jorge DubcovskyAbstract:High Grain Protein content (GPC) is a frequent target of wheat breeding programmes because of its positive effect on bread and pasta quality. A wild wheat allele at the Gpc-B1 locus with a significant impact on this trait was identified previously. The precise mapping of several senescence-related traits in a set of tetraploid recombinant substitution lines (RSLs) segregating for Gpc-B1 is reported here. Flag leaf chlorophyll degradation, change in peduncle colour, and spike water content were completely linked to the Gpc-B1 locus and to the differences in GPC within a 0.3 cM interval corresponding to a physical distance of only 250 kb. The effect of Gpc-B1 was also examined in different environments and genetic backgrounds using a set of tetraploid and hexaploid pairs of isogenic lines. The results were consistent with those observed in the RSLs. The high GPC allele conferred a shorter duration of Grain fill due to earlier flag leaf senescence and increased GPC in all four genetic backgrounds. The effect on Grain size was more variable, depending on the genotype-environment combinations. These results are consistent with a model in which the wild-type allele of Gpc-B1 accelerates senescence in flag leaves producing pleiotropic effects on nitrogen remobilization, total GPC, and Grain size.
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high temperature adult plant htap stripe rust resistance gene yr36 from triticum turgidum ssp dicoccoides is closely linked to the Grain Protein content locus gpc b1
Theoretical and Applied Genetics, 2005Co-Authors: Cristobal Uauy, Assaf Distelfeld, Tzion Fahima, Oswaldo Chicaiza, Juan Carlos Brevis, I A Khan, Xianming Chen, L F Jackson, Jorge DubcovskyAbstract:Several new races of the stripe rust pathogen have become frequent throughout the wheat growing regions of the United States since 2000. These new races are virulent to most of the wheat seedling resistance genes limiting the resistance sources that can be used to combat this pathogen. High-temperature adult-plant (HTAP) stripe rust resistance has proven to be more durable than seedling resistance due to its non-race-specific nature, but its use is limited by the lack of mapping information. We report here the identification of a new HTAP resistance gene from Triticum turgidum ssp. dicoccoides (DIC) designated as Yr36. Lines carrying this gene were susceptible to almost all the stripe rust pathogen races tested at the seedling stage but showed adult-plant resistance to the prevalent races in California when tested at high diurnal temperatures. Isogenic lines for this gene were developed by six backcross generations. Field tests in two locations showed increased levels of field resistance to stripe rust and increased yields in isogenic lines carrying the Yr36 gene compared to those without the gene. Recombinant substitution lines of chromosome 6B from DIC in the isogenic background of durum cv. Langdon were used to map the Yr36 gene on the short arm of chromosome 6B completely linked to Xbarc101, and within a 2-cM interval defined by PCR-based markers Xucw71 and Xbarc136. Flanking locus Xucw71 is also closely linked to the Grain Protein content locus Gpc-B1 (0.3-cM). Marker-assisted selection strategies are presented to improve stripe rust resistance and simultaneously select for high or low Gpc-B1 alleles.
