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PICARA, an analytical pipeline providing probabilistic inference about a priori candidates genes underlying genome-wide association QTL in plants.

Sat, 05/04/2013 - 05:45
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PICARA, an analytical pipeline providing probabilistic inference about a priori candidates genes underlying genome-wide association QTL in plants.

PLoS One. 2012;7(11):e46596

Authors: Chen C, DeClerck G, Tian F, Spooner W, McCouch S, Buckler E

Abstract
PICARA is an analytical pipeline designed to systematically summarize observed SNP/trait associations identified by genome wide association studies (GWAS) and to identify candidate genes involved in the regulation of complex trait variation. The pipeline provides probabilistic inference about a priori candidate genes using integrated information derived from genome-wide association signals, gene homology, and curated gene sets embedded in pathway descriptions. In this paper, we demonstrate the performance of PICARA using data for flowering time variation in maize - a key trait for geographical and seasonal adaption of plants. Among 406 curated flowering time-related genes from Arabidopsis, we identify 61 orthologs in maize that are significantly enriched for GWAS SNP signals, including key regulators such as FT (Flowering Locus T) and GI (GIGANTEA), and genes centered in the Arabidopsis circadian pathway, including TOC1 (Timing of CAB Expression 1) and LHY (Late Elongated Hypocotyl). In addition, we discover a regulatory feature that is characteristic of these a priori flowering time candidates in maize. This new probabilistic analytical pipeline helps researchers infer the functional significance of candidate genes associated with complex traits and helps guide future experiments by providing statistical support for gene candidates based on the integration of heterogeneous biological information.

PMID: 23144785 [PubMed - indexed for MEDLINE]

Genomics of gene banks: A case study in rice.

Sat, 05/04/2013 - 05:45
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Genomics of gene banks: A case study in rice.

Am J Bot. 2012 Feb;99(2):407-23

Authors: McCouch SR, McNally KL, Wang W, Sackville Hamilton R

Abstract
Only a small fraction of the naturally occurring genetic diversity available in the world's germplasm repositories has been explored to date, but this is expected to change with the advent of affordable, high-throughput genotyping and sequencing technology. It is now possible to examine genome-wide patterns of natural variation and link sequence polymorphisms with downstream phenotypic consequences. In this paper, we discuss how dramatic changes in the cost and efficiency of sequencing and genotyping are revolutionizing the way gene bank scientists approach the responsibilities of their job. Sequencing technology provides a set of tools that can be used to enhance the quality, efficiency, and cost-effectiveness of gene bank operations, the depth of scientific knowledge of gene bank holdings, and the level of public interest in natural variation. As a result, gene banks have the chance to take on new life. Previously seen as "warehouses" where seeds were diligently maintained, but evolutionarily frozen in time, gene banks could transform into vibrant research centers that actively investigate the genetic potential of their holdings. In this paper, we will discuss how genotyping and sequencing can be integrated into the activities of a modern gene bank to revolutionize the way scientists document the genetic identity of their accessions; track seed lots, varieties, and alleles; identify duplicates; and rationalize active collections, and how the availability of genomics data are likely to motivate innovative collaborations with the larger research and breeding communities to engage in systematic and rigorous phenotyping and multilocation evaluation of the genetic resources in gene banks around the world. The objective is to understand and eventually predict how variation at the DNA level helps determine the phenotypic potential of an individual or population. Leadership and vision are needed to coordinate the characterization of collections and to integrate genotypic and phenotypic information in ways that will illuminate the value of these resources. Genotyping of collections represents a powerful starting point that will enable gene banks to become more effective as stewards of crop biodiversity.

PMID: 22314574 [PubMed - indexed for MEDLINE]

Next-generation phenotyping: requirements and strategies for enhancing our understanding of genotype-phenotype relationships and its relevance to crop improvement.

Tue, 04/23/2013 - 05:45
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Next-generation phenotyping: requirements and strategies for enhancing our understanding of genotype-phenotype relationships and its relevance to crop improvement.

Theor Appl Genet. 2013 Mar 8;

Authors: Cobb JN, Declerck G, Greenberg A, Clark R, McCouch S

Abstract
More accurate and precise phenotyping strategies are necessary to empower high-resolution linkage mapping and genome-wide association studies and for training genomic selection models in plant improvement. Within this framework, the objective of modern phenotyping is to increase the accuracy, precision and throughput of phenotypic estimation at all levels of biological organization while reducing costs and minimizing labor through automation, remote sensing, improved data integration and experimental design. Much like the efforts to optimize genotyping during the 1980s and 1990s, designing effective phenotyping initiatives today requires multi-faceted collaborations between biologists, computer scientists, statisticians and engineers. Robust phenotyping systems are needed to characterize the full suite of genetic factors that contribute to quantitative phenotypic variation across cells, organs and tissues, developmental stages, years, environments, species and research programs. Next-generation phenotyping generates significantly more data than previously and requires novel data management, access and storage systems, increased use of ontologies to facilitate data integration, and new statistical tools for enhancing experimental design and extracting biologically meaningful signal from environmental and experimental noise. To ensure relevance, the implementation of efficient and informative phenotyping experiments also requires familiarity with diverse germplasm resources, population structures, and target populations of environments. Today, phenotyping is quickly emerging as the major operational bottleneck limiting the power of genetic analysis and genomic prediction. The challenge for the next generation of quantitative geneticists and plant breeders is not only to understand the genetic basis of complex trait variation, but also to use that knowledge to efficiently synthesize twenty-first century crop varieties.

PMID: 23471459 [PubMed - as supplied by publisher]

High-throughput 2D root system phenotyping platform facilitates genetic analysis of root growth and development.

Tue, 11/13/2012 - 05:45

High-throughput 2D root system phenotyping platform facilitates genetic analysis of root growth and development.

Plant Cell Environ. 2012 Aug 5;

Authors: Clark RT, Famoso AN, Zhao K, Shaff JE, Craft EJ, Bustamante CD, McCouch SR, Aneshansley DJ, Kochian LV

Abstract
High-throughput phenotyping of root systems requires a combination of specialized techniques and adaptable plant growth, root imaging and software tools. A custom phenotyping platform was designed to capture images of whole root systems, and novel software tools were developed to process and analyze these images. The platform and its components are adaptable to a wide range root phenotyping studies using diverse growth systems (hydroponics, paper pouches, gel and soil) involving several plant species, including, but not limited to rice, maize, sorghum, tomato and Arabidopsis. The RootReader2D software tool is free and publicly available and was designed with both user-guided and automated features that increase flexibility and enhance efficiency when measuring root growth traits from specific roots or entire root systems during large-scale phenotyping studies. To demonstrate the unique capabilities and high-throughput capacity of this phenotyping platform for studying root systems, genome-wide association studies on rice (Oryza sativa) and maize (Zea mays) root growth were performed and root traits related to aluminum (Al) tolerance were analyzed on the parents of the maize nested association mapping (NAM) population. © 2012 Blackwell Publishing Ltd.

PMID: 22860896 [PubMed - as supplied by publisher]

("1988"[Publication Date] : "3000"[Publication Date]) AND (McCouch S[Author]); +96 new citations

Wed, 07/25/2012 - 16:45

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Resequencing 50 accessions of cultivated and wild rice yields markers for identifying agronomically important genes.

Wed, 07/25/2012 - 15:45
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Resequencing 50 accessions of cultivated and wild rice yields markers for identifying agronomically important genes.

Nat Biotechnol. 2012 Jan;30(1):105-11

Authors: Xu X, Liu X, Ge S, Jensen JD, Hu F, Li X, Dong Y, Gutenkunst RN, Fang L, Huang L, Li J, He W, Zhang G, Zheng X, Zhang F, Li Y, Yu C, Kristiansen K, Zhang X, Wang J, Wright M, McCouch S, Nielsen R, Wang J, Wang W

Abstract
Rice is a staple crop that has undergone substantial phenotypic and physiological changes during domestication. Here we resequenced the genomes of 40 cultivated accessions selected from the major groups of rice and 10 accessions of their wild progenitors (Oryza rufipogon and Oryza nivara) to >15 × raw data coverage. We investigated genome-wide variation patterns in rice and obtained 6.5 million high-quality single nucleotide polymorphisms (SNPs) after excluding sites with missing data in any accession. Using these population SNP data, we identified thousands of genes with significantly lower diversity in cultivated but not wild rice, which represent candidate regions selected during domestication. Some of these variants are associated with important biological features, whereas others have yet to be functionally characterized. The molecular markers we have identified should be valuable for breeding and for identifying agronomically important genes in rice.

PMID: 22158310 [PubMed - indexed for MEDLINE]

Genome-wide association mapping reveals a rich genetic architecture of complex traits in Oryza sativa.

Wed, 07/25/2012 - 15:45
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Genome-wide association mapping reveals a rich genetic architecture of complex traits in Oryza sativa.

Nat Commun. 2011;2:467

Authors: Zhao K, Tung CW, Eizenga GC, Wright MH, Ali ML, Price AH, Norton GJ, Islam MR, Reynolds A, Mezey J, McClung AM, Bustamante CD, McCouch SR

Abstract
Asian rice, Oryza sativa is a cultivated, inbreeding species that feeds over half of the world's population. Understanding the genetic basis of diverse physiological, developmental, and morphological traits provides the basis for improving yield, quality and sustainability of rice. Here we show the results of a genome-wide association study based on genotyping 44,100 SNP variants across 413 diverse accessions of O. sativa collected from 82 countries that were systematically phenotyped for 34 traits. Using cross-population-based mapping strategies, we identified dozens of common variants influencing numerous complex traits. Significant heterogeneity was observed in the genetic architecture associated with subpopulation structure and response to environment. This work establishes an open-source translational research platform for genome-wide association studies in rice that directly links molecular variation in genes and metabolic pathways with the germplasm resources needed to accelerate varietal development and crop improvement.

PMID: 21915109 [PubMed - indexed for MEDLINE]

Genetic architecture of aluminum tolerance in rice (Oryza sativa) determined through genome-wide association analysis and QTL mapping.

Wed, 07/25/2012 - 15:45
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Genetic architecture of aluminum tolerance in rice (Oryza sativa) determined through genome-wide association analysis and QTL mapping.

PLoS Genet. 2011 Aug;7(8):e1002221

Authors: Famoso AN, Zhao K, Clark RT, Tung CW, Wright MH, Bustamante C, Kochian LV, McCouch SR

Abstract
Aluminum (Al) toxicity is a primary limitation to crop productivity on acid soils, and rice has been demonstrated to be significantly more Al tolerant than other cereal crops. However, the mechanisms of rice Al tolerance are largely unknown, and no genes underlying natural variation have been reported. We screened 383 diverse rice accessions, conducted a genome-wide association (GWA) study, and conducted QTL mapping in two bi-parental populations using three estimates of Al tolerance based on root growth. Subpopulation structure explained 57% of the phenotypic variation, and the mean Al tolerance in Japonica was twice that of Indica. Forty-eight regions associated with Al tolerance were identified by GWA analysis, most of which were subpopulation-specific. Four of these regions co-localized with a priori candidate genes, and two highly significant regions co-localized with previously identified QTLs. Three regions corresponding to induced Al-sensitive rice mutants (ART1, STAR2, Nrat1) were identified through bi-parental QTL mapping or GWA to be involved in natural variation for Al tolerance. Haplotype analysis around the Nrat1 gene identified susceptible and tolerant haplotypes explaining 40% of the Al tolerance variation within the aus subpopulation, and sequence analysis of Nrat1 identified a trio of non-synonymous mutations predictive of Al sensitivity in our diversity panel. GWA analysis discovered more phenotype-genotype associations and provided higher resolution, but QTL mapping identified critical rare and/or subpopulation-specific alleles not detected by GWA analysis. Mapping using Indica/Japonica populations identified QTLs associated with transgressive variation where alleles from a susceptible aus or indica parent enhanced Al tolerance in a tolerant Japonica background. This work supports the hypothesis that selectively introgressing alleles across subpopulations is an efficient approach for trait enhancement in plant breeding programs and demonstrates the fundamental importance of subpopulation in interpreting and manipulating the genetics of complex traits in rice.

PMID: 21829395 [PubMed - indexed for MEDLINE]

Three-dimensional root phenotyping with a novel imaging and software platform.

Wed, 07/25/2012 - 15:45
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Three-dimensional root phenotyping with a novel imaging and software platform.

Plant Physiol. 2011 Jun;156(2):455-65

Authors: Clark RT, MacCurdy RB, Jung JK, Shaff JE, McCouch SR, Aneshansley DJ, Kochian LV

Abstract
A novel imaging and software platform was developed for the high-throughput phenotyping of three-dimensional root traits during seedling development. To demonstrate the platform's capacity, plants of two rice (Oryza sativa) genotypes, Azucena and IR64, were grown in a transparent gellan gum system and imaged daily for 10 d. Rotational image sequences consisting of 40 two-dimensional images were captured using an optically corrected digital imaging system. Three-dimensional root reconstructions were generated and analyzed using a custom-designed software, RootReader3D. Using the automated and interactive capabilities of RootReader3D, five rice root types were classified and 27 phenotypic root traits were measured to characterize these two genotypes. Where possible, measurements from the three-dimensional platform were validated and were highly correlated with conventional two-dimensional measurements. When comparing gellan gum-grown plants with those grown under hydroponic and sand culture, significant differences were detected in morphological root traits (P < 0.05). This highly flexible platform provides the capacity to measure root traits with a high degree of spatial and temporal resolution and will facilitate novel investigations into the development of entire root systems or selected components of root systems. In combination with the extensive genetic resources that are now available, this platform will be a powerful resource to further explore the molecular and genetic determinants of root system architecture.

PMID: 21454799 [PubMed - indexed for MEDLINE]

Exceptional lability of a genomic complex in rice and its close relatives revealed by interspecific and intraspecific comparison and population analysis.

Wed, 07/25/2012 - 15:45
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Exceptional lability of a genomic complex in rice and its close relatives revealed by interspecific and intraspecific comparison and population analysis.

BMC Genomics. 2011;12:142

Authors: Tian Z, Yu Y, Lin F, Yu Y, Sanmiguel PJ, Wing RA, McCouch SR, Ma J, Jackson SA

Abstract
BACKGROUND: Extensive DNA rearrangement of genic colinearity, as revealed by comparison of orthologous genomic regions, has been shown to be a general concept describing evolutionary dynamics of plant genomes. However, the nature, timing, lineages and adaptation of local genomic rearrangement in closely related species (e.g., within a genus) and haplotype variation of genomic rearrangement within populations have not been well documented.
RESULTS: We previously identified a hotspot for genic rearrangement and transposon accumulation in the Orp region of Asian rice (Oryza sativa, AA) by comparison with its orthologous region in sorghum. Here, we report the comparative analysis of this region with its orthologous regions in the wild progenitor species (O. nivara, AA) of Asian rice and African rice (O. glaberrima) using the BB genome Oryza species (O. punctata) as an outgroup, and investigation of transposon insertion sites and a segmental inversion event in the AA genomes at the population level. We found that Orp region was primarily and recently expanded in the Asian rice species O. sativa and O. nivara. LTR-retrotransposons shared by the three AA-genomic regions have been fixed in all the 94 varieties that represent different populations of the AA-genome species/subspecies, indicating their adaptive role in genome differentiation. However, LTR-retrotransposons unique to either O. nivara or O. sativa regions exhibited dramatic haplotype variation regarding their presence or absence between or within populations/subpopulations.
CONCLUSIONS: The LTR-retrotransposon insertion hotspot in the Orp region was formed recently, independently and concurrently in different AA-genome species, and that the genic rearrangements detected in different species appear to be differentially triggered by transposable elements. This region is located near the end of the short arm of chromosome 8 and contains a high proportion of LTR-retrotransposons similar to observed in the centromeric region of this same chromosome, and thus may represent a genomic region that has recently switched from euchromatic to heterochromatic states. The haplotype variation of LTR-retrotransposon insertions within this region reveals substantial admixture among various subpopulations as established by molecular markers at the whole genome level, and can be used to develop retrotransposon junction markers for simple and rapid classification of O. sativa germplasm.

PMID: 21385395 [PubMed - indexed for MEDLINE]

Gramene database in 2010: updates and extensions.

Wed, 07/25/2012 - 15:45
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Gramene database in 2010: updates and extensions.

Nucleic Acids Res. 2011 Jan;39(Database issue):D1085-94

Authors: Youens-Clark K, Buckler E, Casstevens T, Chen C, Declerck G, Derwent P, Dharmawardhana P, Jaiswal P, Kersey P, Karthikeyan AS, Lu J, McCouch SR, Ren L, Spooner W, Stein JC, Thomason J, Wei S, Ware D

Abstract
Now in its 10th year, the Gramene database (http://www.gramene.org) has grown from its primary focus on rice, the first fully-sequenced grass genome, to become a resource for major model and crop plants including Arabidopsis, Brachypodium, maize, sorghum, poplar and grape in addition to several species of rice. Gramene began with the addition of an Ensembl genome browser and has expanded in the last decade to become a robust resource for plant genomics hosting a wide array of data sets including quantitative trait loci (QTL), metabolic pathways, genetic diversity, genes, proteins, germplasm, literature, ontologies and a fully-structured markers and sequences database integrated with genome browsers and maps from various published studies (genetic, physical, bin, etc.). In addition, Gramene now hosts a variety of web services including a Distributed Annotation Server (DAS), BLAST and a public MySQL database. Twice a year, Gramene releases a major build of the database and makes interim releases to correct errors or to make important updates to software and/or data.

PMID: 21076153 [PubMed - indexed for MEDLINE]

ALCHEMY: a reliable method for automated SNP genotype calling for small batch sizes and highly homozygous populations.

Wed, 07/25/2012 - 15:45
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ALCHEMY: a reliable method for automated SNP genotype calling for small batch sizes and highly homozygous populations.

Bioinformatics. 2010 Dec 1;26(23):2952-60

Authors: Wright MH, Tung CW, Zhao K, Reynolds A, McCouch SR, Bustamante CD

Abstract
MOTIVATION: The development of new high-throughput genotyping products requires a significant investment in testing and training samples to evaluate and optimize the product before it can be used reliably on new samples. One reason for this is current methods for automated calling of genotypes are based on clustering approaches which require a large number of samples to be analyzed simultaneously, or an extensive training dataset to seed clusters. In systems where inbred samples are of primary interest, current clustering approaches perform poorly due to the inability to clearly identify a heterozygote cluster.
RESULTS: As part of the development of two custom single nucleotide polymorphism genotyping products for Oryza sativa (domestic rice), we have developed a new genotype calling algorithm called 'ALCHEMY' based on statistical modeling of the raw intensity data rather than modelless clustering. A novel feature of the model is the ability to estimate and incorporate inbreeding information on a per sample basis allowing accurate genotyping of both inbred and heterozygous samples even when analyzed simultaneously. Since clustering is not used explicitly, ALCHEMY performs well on small sample sizes with accuracy exceeding 99% with as few as 18 samples.
AVAILABILITY: ALCHEMY is available for both commercial and academic use free of charge and distributed under the GNU General Public License at http://alchemy.sourceforge.net/
CONTACT: mhw6@cornell.edu
SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

PMID: 20926420 [PubMed - indexed for MEDLINE]

Development of a novel aluminum tolerance phenotyping platform used for comparisons of cereal aluminum tolerance and investigations into rice aluminum tolerance mechanisms.

Wed, 07/25/2012 - 15:45
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Development of a novel aluminum tolerance phenotyping platform used for comparisons of cereal aluminum tolerance and investigations into rice aluminum tolerance mechanisms.

Plant Physiol. 2010 Aug;153(4):1678-91

Authors: Famoso AN, Clark RT, Shaff JE, Craft E, McCouch SR, Kochian LV

Abstract
The genetic and physiological mechanisms of aluminum (Al) tolerance have been well studied in certain cereal crops, and Al tolerance genes have been identified in sorghum (Sorghum bicolor) and wheat (Triticum aestivum). Rice (Oryza sativa) has been reported to be highly Al tolerant; however, a direct comparison of rice and other cereals has not been reported, and the mechanisms of rice Al tolerance are poorly understood. To facilitate Al tolerance phenotyping in rice, a high-throughput imaging system and root quantification computer program was developed, permitting quantification of the entire root system, rather than just the longest root. Additionally, a novel hydroponic solution was developed and optimized for Al tolerance screening in rice and compared with the Yoshida's rice solution commonly used for rice Al tolerance studies. To gain a better understanding of Al tolerance in cereals, comparisons of Al tolerance across cereal species were conducted at four Al concentrations using seven to nine genetically diverse genotypes of wheat, maize (Zea mays), sorghum, and rice. Rice was significantly more tolerant than maize, wheat, and sorghum at all Al concentrations, with the mean Al tolerance level for rice found to be 2- to 6-fold greater than that in maize, wheat, and sorghum. Physiological experiments were conducted on a genetically diverse panel of more than 20 rice genotypes spanning the range of rice Al tolerance and compared with two maize genotypes to determine if rice utilizes the well-described Al tolerance mechanism of root tip Al exclusion mediated by organic acid exudation. These results clearly demonstrate that the extremely high levels of rice Al tolerance are mediated by a novel mechanism, which is independent of root tip Al exclusion.

PMID: 20538888 [PubMed - indexed for MEDLINE]

Genomic diversity and introgression in O. sativa reveal the impact of domestication and breeding on the rice genome.

Wed, 07/25/2012 - 15:45
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Genomic diversity and introgression in O. sativa reveal the impact of domestication and breeding on the rice genome.

PLoS One. 2010;5(5):e10780

Authors: Zhao K, Wright M, Kimball J, Eizenga G, McClung A, Kovach M, Tyagi W, Ali ML, Tung CW, Reynolds A, Bustamante CD, McCouch SR

Abstract
BACKGROUND: The domestication of Asian rice (Oryza sativa) was a complex process punctuated by episodes of introgressive hybridization among and between subpopulations. Deep genetic divergence between the two main varietal groups (Indica and Japonica) suggests domestication from at least two distinct wild populations. However, genetic uniformity surrounding key domestication genes across divergent subpopulations suggests cultural exchange of genetic material among ancient farmers.
METHODOLOGY/PRINCIPAL FINDINGS: In this study, we utilize a novel 1,536 SNP panel genotyped across 395 diverse accessions of O. sativa to study genome-wide patterns of polymorphism, to characterize population structure, and to infer the introgression history of domesticated Asian rice. Our population structure analyses support the existence of five major subpopulations (indica, aus, tropical japonica, temperate japonica and GroupV) consistent with previous analyses. Our introgression analysis shows that most accessions exhibit some degree of admixture, with many individuals within a population sharing the same introgressed segment due to artificial selection. Admixture mapping and association analysis of amylose content and grain length illustrate the potential for dissecting the genetic basis of complex traits in domesticated plant populations.
CONCLUSIONS/SIGNIFICANCE: Genes in these regions control a myriad of traits including plant stature, blast resistance, and amylose content. These analyses highlight the power of population genomics in agricultural systems to identify functionally important regions of the genome and to decipher the role of human-directed breeding in refashioning the genomes of a domesticated species.

PMID: 20520727 [PubMed - indexed for MEDLINE]

Inactivation of the CTD phosphatase-like gene OsCPL1 enhances the development of the abscission layer and seed shattering in rice.

Wed, 07/25/2012 - 15:45
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Inactivation of the CTD phosphatase-like gene OsCPL1 enhances the development of the abscission layer and seed shattering in rice.

Plant J. 2010 Jan;61(1):96-106

Authors: Ji H, Kim SR, Kim YH, Kim H, Eun MY, Jin ID, Cha YS, Yun DW, Ahn BO, Lee MC, Lee GS, Yoon UH, Lee JS, Lee YH, Suh SC, Jiang W, Yang JI, Jin P, McCouch SR, An G, Koh HJ

Abstract
Although susceptibility to seed shattering causes severe yield loss during cereal crop harvest, it is an adaptive trait for seed dispersal in wild plants. We previously identified a recessive shattering locus, sh-h, from the rice shattering mutant line Hsh that carries an enhanced abscission layer. Here, we further mapped sh-h to a 34-kb region on chromosome 7 by analyzing 240 F(2) plants and five F(3) lines from the cross between Hsh and Blue&Gundil. Hsh had a point mutation at the 3' splice site of the seventh intron within LOC_Os07g10690, causing a 15-bp deletion of its mRNA as a result of altered splicing. Two transferred DNA (T-DNA) insertion mutants and one point mutant exhibited the enhanced shattering phenotype, confirming that LOC_Os07g10690 is indeed the sh-h gene. RNA interference (RNAi) transgenic lines with suppressed expression of this gene exhibited greater shattering. This gene, which encodes a protein containing a conserved carboxy-terminal domain (CTD) phosphatase domain, was named Oryza sativa CTD phosphatase-like 1 (OsCPL1). Subcellular localization and biochemical analysis revealed that the OsCPL1 protein is a nuclear phosphatase, a common characteristic of metazoan CTD phosphatases involved in cell differentiation. These results demonstrate that OsCPL1 represses differentiation of the abscission layer during panicle development.

PMID: 19807881 [PubMed - indexed for MEDLINE]

The origin and evolution of fragrance in rice (Oryza sativa L.).

Wed, 07/25/2012 - 15:45
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The origin and evolution of fragrance in rice (Oryza sativa L.).

Proc Natl Acad Sci U S A. 2009 Aug 25;106(34):14444-9

Authors: Kovach MJ, Calingacion MN, Fitzgerald MA, McCouch SR

Abstract
Fragrance in the grain is one of the most highly valued grain quality traits in rice, yet the origin and evolution of the betaine aldehyde dehydrogenase gene (BADH2) underlying this trait remains unclear. In this study, we identify eight putatively nonfunctional alleles of the BADH2 gene and show that these alleles have distinct geographic and genetic origins. Despite multiple origins of the fragrance trait, a single allele, badh2.1, is the predominant allele in virtually all fragrant rice varieties today, including the widely recognized Basmati and Jasmine types. Haplotype analysis allowed us to establish a single origin of the badh2.1 allele within the Japonica varietal group and demonstrate the introgression of this allele from Japonica to Indica. Basmati-like accessions were nearly identical to the ancestral Japonica haplotype across a 5.3-Mb region flanking BADH2 regardless of their fragrance phenotype, demonstrating a close evolutionary relationship between Basmati varieties and the Japonica gene pool. These results clarify the relationships among fragrant rice varieties and challenge the traditional assumption that the fragrance trait arose in the Indica varietal group.

PMID: 19706531 [PubMed - indexed for MEDLINE]

Gramene QTL database: development, content and applications.

Wed, 07/25/2012 - 15:45
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Gramene QTL database: development, content and applications.

Database (Oxford). 2009;2009:bap005

Authors: Ni J, Pujar A, Youens-Clark K, Yap I, Jaiswal P, Tecle I, Tung CW, Ren L, Spooner W, Wei X, Avraham S, Ware D, Stein L, McCouch S

Abstract
Gramene is a comparative information resource for plants that integrates data across diverse data domains. In this article, we describe the development of a quantitative trait loci (QTL) database and illustrate how it can be used to facilitate both the forward and reverse genetics research. The QTL database contains the largest online collection of rice QTL data in the world. Using flanking markers as anchors, QTLs originally reported on individual genetic maps have been systematically aligned to the rice sequence where they can be searched as standard genomic features. Researchers can determine whether a QTL co-localizes with other QTLs detected in independent experiments and can combine data from multiple studies to improve the resolution of a QTL position. Candidate genes falling within a QTL interval can be identified and their relationship to particular phenotypes can be inferred based on functional annotations provided by ontology terms. Mutations identified in functional genomics populations and association mapping panels can be aligned with QTL regions to facilitate fine mapping and validation of gene-phenotype associations. By assembling and integrating diverse types of data and information across species and levels of biological complexity, the QTL database enhances the potential to understand and utilize QTL information in biological research.

PMID: 20157478 [PubMed - as supplied by publisher]

Dissection of a QTL reveals an adaptive, interacting gene complex associated with transgressive variation for flowering time in rice.

Wed, 07/25/2012 - 15:45
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Dissection of a QTL reveals an adaptive, interacting gene complex associated with transgressive variation for flowering time in rice.

Theor Appl Genet. 2010 Mar;120(5):895-908

Authors: Maas LF, McClung A, McCouch S

Abstract
A days to heading QTL (dth1.1) located on the short arm of rice chromosome 1 was sub-divided into eight sub-introgression lines (SILs) to analyze the genetic basis of transgressive variation for flowering time. Each SIL contained one or more introgression(s) from O. rufipogon in the genetic background of the elite Oryza sativa cultivar, Jefferson. Each introgression was defined at high resolution using molecular markers and those in the dth1.1 region were associated with the presence of one or more flowering time genes (GI, SOC1, FT-L8, EMF1, and PNZIP). SILs and controls were evaluated for flowering time under both short- and long-day growing conditions. Under short-day lengths, lines with introgressions carrying combinations of linked flowering time genes (GI/SOC1, SOC1/FT-L8, GI/SOC1/FT-L8 and EMF1/PNZIP) from the late parent, O. rufipogon, flowered earlier than the recurrent parent, Jefferson, while recombinant lines carrying smaller introgressions marked by the presence of GI, SOC1, EMF1 or PNZIP alone no longer flowered early. Under long-day length, lines carrying SOC1/FT-L8, SOC1 or PNZIP flowered early, while those carrying GI or EMF1 delayed flowering. Across all experiments and in the field, only SIL_SOC1/FT-L8 was consistently early. A preliminary yield evaluation indicated that the transgressive early flowering observed in several of the SILs was also associated with a measurable and positive effect on yield. These SILs represent a new source of variation that can be used in breeding programs to manipulate flowering time in rice cultivars without the reduction in yield that is often associated with early maturing phenotypes.

PMID: 19949767 [PubMed - indexed for MEDLINE]

A universal core genetic map for rice.

Wed, 07/25/2012 - 15:45
Related Articles

A universal core genetic map for rice.

Theor Appl Genet. 2010 Feb;120(3):563-72

Authors: Orjuela J, Garavito A, Bouniol M, Arbelaez JD, Moreno L, Kimball J, Wilson G, Rami JF, Tohme J, McCouch SR, Lorieux M

Abstract
To facilitate the creation of easily comparable, low-resolution genetic maps with evenly distributed markers in rice (Oryza sativa L.), we conceived of and developed a Universal Core Genetic Map (UCGM). With this aim, we derived a set of 165 anchors, representing clusters of three microsatellite or simple sequence repeat (SSR) markers arranged into non-recombining groups. Each anchor consists of at least three, closely linked SSRs, located within a distance below the genetic resolution provided by common, segregating populations (<500 individuals). We chose anchors that were evenly distributed across the rice chromosomes, with spacing between 2 and 3.5 Mbp (except in the telomeric regions, where spacing was 1.5 Mbp). Anchor selection was performed using in silico tools and data: the O. sativa cv. Nipponbare rice genome sequence, the CHARM tool, information from the Gramene database and the OrygenesDB database. Sixteen AA-genome accessions of the Oryza genus were used to evaluate polymorphisms for the selected markers, including accessions from O. sativa, O. glaberrima, O. barthii, O. rufipogon, O. glumaepatula and O. meridionalis. High levels of polymorphism were found for the tested O. sativa x O. glaberrima or O. sativa x wild rice combinations. We developed Paddy Map, a simple database that is helpful in selecting optimal sets of polymorphic SSRs for any cross that involves the previously mentioned species. Validation of the UCGM was done by using it to develop three interspecific genetic maps and by comparing genetic SSR locations with their physical positions on the rice pseudomolecules. In this study, we demonstrate that the UCGM is a useful tool for the rice genetics and breeding community, especially in strategies based on interspecific hybridisation.

PMID: 19847389 [PubMed - indexed for MEDLINE]

Not just a grain of rice: the quest for quality.

Sun, 04/25/2010 - 22:08
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Not just a grain of rice: the quest for quality.

Trends Plant Sci. 2009 Mar;14(3):133-9

Authors: Fitzgerald MA, McCouch SR, Hall RD

A better understanding of the factors that contribute to the overall grain quality of rice (Oryza sativa) will lay the foundation for developing new breeding and selection strategies for combining high quality, with high yield. This is necessary to meet the growing global demand for high quality rice while offering producing countries additional opportunities for generating higher export revenues. Several recent developments in genetics, genomics, metabolomics and phenomics are enhancing our understanding of the pathways that determine several quality traits. New research strategies, as well as access to the draft of the rice genome, will not only advance our understanding of the molecular mechanisms that lead to quality rice but will also pave the way for efficient and targeted grain improvement.

PMID: 19230745 [PubMed - indexed for MEDLINE]

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