Publications by authors named "Sujan Mamidi"

30 Publications

  • Page 1 of 1

Genetic dissection of natural variation in oilseed traits of camelina by whole-genome resequencing and QTL mapping.

Plant Genome 2021 Jun 9:e20110. Epub 2021 Jun 9.

Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT, 59717, USA.

Camelina [Camelina sativa (L.) Crantz] is an oilseed crop in the Brassicaceae family that is currently being developed as a source of bioenergy and healthy fatty acids. To facilitate modern breeding efforts through marker-assisted selection and biotechnology, we evaluated genetic variation among a worldwide collection of 222 camelina accessions. We performed whole-genome resequencing to obtain single nucleotide polymorphism (SNP) markers and to analyze genomic diversity. We also conducted phenotypic field evaluations in two consecutive seasons for variations in key agronomic traits related to oilseed production such as seed size, oil content (OC), fatty acid composition, and flowering time. We determined the population structure of the camelina accessions using 161,301 SNPs. Further, we identified quantitative trait loci (QTL) and candidate genes controlling the above field-evaluated traits by genome-wide association studies (GWAS) complemented with linkage mapping using a recombinant inbred line (RIL) population. Characterization of the natural variation at the genome and phenotypic levels provides valuable resources to camelina genetic studies and crop improvement. The QTL and candidate genes should assist in breeding of advanced camelina varieties that can be integrated into the cropping systems for the production of high yield of oils of desired fatty acid composition.
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http://dx.doi.org/10.1002/tpg2.20110DOI Listing
June 2021

The tepary bean genome provides insight into evolution and domestication under heat stress.

Nat Commun 2021 05 11;12(1):2638. Epub 2021 May 11.

Department of Plant Sciences and Genomics and Bioinformatics Program, North Dakota State University, Fargo, ND, USA.

Tepary bean (Phaseolus acutifolis A. Gray), native to the Sonoran Desert, is highly adapted to heat and drought. It is a sister species of common bean (Phaseolus vulgaris L.), the most important legume protein source for direct human consumption, and whose production is threatened by climate change. Here, we report on the tepary genome including exploration of possible mechanisms for resilience to moderate heat stress and a reduced disease resistance gene repertoire, consistent with adaptation to arid and hot environments. Extensive collinearity and shared gene content among these Phaseolus species will facilitate engineering climate adaptation in common bean, a key food security crop, and accelerate tepary bean improvement.
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http://dx.doi.org/10.1038/s41467-021-22858-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8113540PMC
May 2021

Genomic mechanisms of climate adaptation in polyploid bioenergy switchgrass.

Nature 2021 02 27;590(7846):438-444. Epub 2021 Jan 27.

School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India.

Long-term climate change and periodic environmental extremes threaten food and fuel security and global crop productivity. Although molecular and adaptive breeding strategies can buffer the effects of climatic stress and improve crop resilience, these approaches require sufficient knowledge of the genes that underlie productivity and adaptation-knowledge that has been limited to a small number of well-studied model systems. Here we present the assembly and annotation of the large and complex genome of the polyploid bioenergy crop switchgrass (Panicum virgatum). Analysis of biomass and survival among 732 resequenced genotypes, which were grown across 10 common gardens that span 1,800 km of latitude, jointly revealed extensive genomic evidence of climate adaptation. Climate-gene-biomass associations were abundant but varied considerably among deeply diverged gene pools. Furthermore, we found that gene flow accelerated climate adaptation during the postglacial colonization of northern habitats through introgression of alleles from a pre-adapted northern gene pool. The polyploid nature of switchgrass also enhanced adaptive potential through the fractionation of gene function, as there was an increased level of heritable genetic diversity on the nondominant subgenome. In addition to investigating patterns of climate adaptation, the genome resources and gene-trait associations developed here provide breeders with the necessary tools to increase switchgrass yield for the sustainable production of bioenergy.
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http://dx.doi.org/10.1038/s41586-020-03127-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7886653PMC
February 2021

A genome assembly and the somatic genetic and epigenetic mutation rate in a wild long-lived perennial Populus trichocarpa.

Genome Biol 2020 10 6;21(1):259. Epub 2020 Oct 6.

Institute for Advanced Study (IAS), Technical University of Munich, Lichtenbergstr. 2a, Garching, Germany.

Background: Plants can transmit somatic mutations and epimutations to offspring, which in turn can affect fitness. Knowledge of the rate at which these variations arise is necessary to understand how plant development contributes to local adaption in an ecoevolutionary context, particularly in long-lived perennials.

Results: Here, we generate a new high-quality reference genome from the oldest branch of a wild Populus trichocarpa tree with two dominant stems which have been evolving independently for 330 years. By sampling multiple, age-estimated branches of this tree, we use a multi-omics approach to quantify age-related somatic changes at the genetic, epigenetic, and transcriptional level. We show that the per-year somatic mutation and epimutation rates are lower than in annuals and that transcriptional variation is mainly independent of age divergence and cytosine methylation. Furthermore, a detailed analysis of the somatic epimutation spectrum indicates that transgenerationally heritable epimutations originate mainly from DNA methylation maintenance errors during mitotic rather than during meiotic cell divisions.

Conclusion: Taken together, our study provides unprecedented insights into the origin of nucleotide and functional variation in a long-lived perennial plant.
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http://dx.doi.org/10.1186/s13059-020-02162-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7539514PMC
October 2020

A genome resource for green millet Setaria viridis enables discovery of agronomically valuable loci.

Nat Biotechnol 2020 10 5;38(10):1203-1210. Epub 2020 Oct 5.

Donald Danforth Plant Science Center, St. Louis, MO, USA.

Wild and weedy relatives of domesticated crops harbor genetic variants that can advance agricultural biotechnology. Here we provide a genome resource for the wild plant green millet (Setaria viridis), a model species for studies of C grasses, and use the resource to probe domestication genes in the close crop relative foxtail millet (Setaria italica). We produced a platinum-quality genome assembly of S. viridis and de novo assemblies for 598 wild accessions and exploited these assemblies to identify loci underlying three traits: response to climate, a 'loss of shattering' trait that permits mechanical harvest and leaf angle, a predictor of yield in many grass crops. With CRISPR-Cas9 genome editing, we validated Less Shattering1 (SvLes1) as a gene whose product controls seed shattering. In S. italica, this gene was rendered nonfunctional by a retrotransposon insertion in the domesticated loss-of-shattering allele SiLes1-TE (transposable element). This resource will enhance the utility of S. viridis for dissection of complex traits and biotechnological improvement of panicoid crops.
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http://dx.doi.org/10.1038/s41587-020-0681-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7536120PMC
October 2020

Genome-wide analysis of the transcriptional response to drought stress in root and leaf of common bean.

Genet Mol Biol 2020 16;43(1):e20180259. Epub 2020 Mar 16.

EMBRAPA Arroz e Feijão, Rod. GO - 462, Km 12, Santo Antônio de Goiás, GO, Brazil.

Genes related to the response to drought stress in leaf and root tissue of drought-susceptible (DS) and tolerant (DT) genotypes were characterized by RNA-Seq. In total, 54,750 transcripts, representative of 28,590 genes, were identified; of these, 1,648 were of high-fidelity (merge of 12 libraries) and described for the first time in the Andean germplasm. From the 1,239 differentially expressed genes (DEGs), 458 were identified in DT, with a predominance of genes in categories of oxidative stress, response to stimulus and kinase activity. Most genes related to oxidation-reduction terms in roots were early triggered in DT (T75) compared to DS (T150) suggestive of a mechanism of tolerance by reducing the damage from ROS. Among the KEGG enriched by DEGs up-regulated in DT leaves, two related to the formation of Sulfur-containing compounds, which are known for their involvement in tolerance to abiotic stresses, were common to all treatments. Through qPCR, 88.64% of the DEGs were validated. A total of 151,283 variants were identified and functional effects estimated for 85,780. The raw data files were submitted to the NCBI database. A transcriptome map revealed new genes and isoforms under drought. These results supports a better understanding of the drought tolerance mechanisms in beans.
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http://dx.doi.org/10.1590/1678-4685-GMB-2018-0259DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7307723PMC
March 2020

The genomic landscape of molecular responses to natural drought stress in Panicum hallii.

Nat Commun 2018 12 6;9(1):5213. Epub 2018 Dec 6.

Department of Integrative Biology, The University of Texas at Austin, Austin, 78712, TX, USA.

Environmental stress is a major driver of ecological community dynamics and agricultural productivity. This is especially true for soil water availability, because drought is the greatest abiotic inhibitor of worldwide crop yields. Here, we test the genetic basis of drought responses in the genetic model for C perennial grasses, Panicum hallii, through population genomics, field-scale gene-expression (eQTL) analysis, and comparison of two complete genomes. While gene expression networks are dominated by local cis-regulatory elements, we observe three genomic hotspots of unlinked trans-regulatory loci. These regulatory hubs are four times more drought responsive than the genome-wide average. Additionally, cis- and trans-regulatory networks are more likely to have opposing effects than expected under neutral evolution, supporting a strong influence of compensatory evolution and stabilizing selection. These results implicate trans-regulatory evolution as a driver of drought responses and demonstrate the potential for crop improvement in drought-prone regions through modification of gene regulatory networks.
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http://dx.doi.org/10.1038/s41467-018-07669-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6283873PMC
December 2018

Population genomics and climate adaptation of a C4 perennial grass, Panicum hallii (Poaceae).

BMC Genomics 2018 Nov 1;19(1):792. Epub 2018 Nov 1.

Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA.

Background: Understanding how and why genetic variation is partitioned across geographic space is of fundamental importance to understanding the nature of biological species. How geographical isolation and local adaptation contribute to the formation of ecotypically differentiated groups of plants is just beginning to be understood through population genomic studies. We used whole genome sequencing combined with association study of climate to discover the drivers of differentiation in the perennial C4 grass Panicum hallii.

Results: Sequencing of 89 natural accessions of P.hallii revealed complex population structure across the species range. Major population genomic separation was found between subspecies P.hallii var. hallii and var. filipes as well as between at least four major unrecognized subgroups within var. hallii. At least 139 genomic SNPs were significantly associated with temperature or precipitation across the range and these SNPs were enriched for non-synonymous substitutions. SNPs associated with temperature and aridity were more often found in or near genes than expected by chance and enriched for putative involvement in dormancy processes, seed maturation, response to hyperosmosis and salinity, abscisic acid metabolism, hormone metabolism, and drought recovery.

Conclusions: Both geography and climate adaptation contribute significantly to patterns of genome-wide variation in P.hallii. Population subgroups within P.hallii may represent early stages in the formation of ecotypes. Climate associated loci identified here represent promising targets for future research in this and other perennial grasses.
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http://dx.doi.org/10.1186/s12864-018-5179-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6211516PMC
November 2018

Genetic Analysis of Flooding Tolerance in an Andean Diversity Panel of Dry Bean ( L.).

Front Plant Sci 2018 6;9:767. Epub 2018 Jun 6.

Department of Plant Sciences, North Dakota State University, Fargo, ND, United States.

Climate change models predict temporal and spatial shifts in precipitation resulting in more frequent incidents of flooding, particularly in regions with poor soil drainage. In these flooding conditions, crop losses are inevitable due to exposure of plants to hypoxia and the spread of root rot diseases. Improving the tolerance of bean cultivars to flooding is crucial to minimize crop losses. In this experiment, we evaluated the phenotypic responses of 277 genotypes from the Andean Diversity Panel to flooding at germination and seedling stages. A randomized complete block design, with a split plot arrangement, was employed for phenotyping germination rate, total weight, shoot weight, root weight, hypocotyl length, SPAD index, adventitious root rate, and survival score. A subset of genotypes ( = 20) were further evaluated under field conditions to assess correlations between field and greenhouse data and to identify the most tolerant genotypes. A genome-wide association study (GWAS) was performed using ~203 K SNP markers to understand the genetic architecture of flooding tolerance in this panel. Survival scores between field and greenhouse data were significantly correlated ( = 0.55, = 0.01). Subsequently, a subset of the most tolerant and susceptible genotypes were evaluated under pathogenic spp. pressure. This experiment revealed a potential link between flooding tolerance and spp. resistance. Several tolerant genotypes were identified that could be used as donor parents in breeding pipelines, especially ADP-429 and ADP-604. Based on the population structure analysis, a subpopulation consisting of 20 genotypes from the Middle American gene pool was detected that also possessed the highest root weight, hypocotyl length, and adventitious root development under flooding conditions. Genomic regions associated with flooding tolerance were identified including a region on Pv08/3.2 Mb, which is associated with germination rate and resides in vicinity of , a central gene involved in response of plants to hypoxia. Furthermore, a QTL at Pv07/4.7 Mb was detected that controls survival score of seedlings under flooding conditions. The association of these QTL with the survivability traits including germination rate and survival score, indicates that these loci can be used in marker-assisted selection breeding to improve flooding tolerance in the Andean germplasm.
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http://dx.doi.org/10.3389/fpls.2018.00767DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5997968PMC
June 2018

White seed color in common bean (Phaseolus vulgaris) results from convergent evolution in the P (pigment) gene.

New Phytol 2018 08 13;219(3):1112-1123. Epub 2018 Jun 13.

Department of Plant Sciences, North Dakota State University, Fargo, ND, 58108, USA.

The presence of seed color in common bean (Phaseolus vulgaris) requires the dominant-acting P (pigment) gene, and white seed is a recessive phenotype in all domesticated races of the species. P was classically associated with seed size, thus describing it as the first genetic marker for a quantitative trait. The molecular structure of P was characterized to understand the selection of white seeds during bean diversification and the relationship of P to seed weight. P was identified by homology searches, a genome-wide association study (GWAS) and gene remodeling, and confirmed by gene silencing. Allelic variation was assessed by a combination of resequencing and marker development, and the relationship between P and seed weight was assessed by a GWAS study. P is a member of clade B of subclass IIIf of plant basic helix-loop-helix (bHLH) proteins. Ten race-specific P alleles conditioned the white seed phenotype, and each causative mutation affected at least one bHLH domain required for color expression. GWAS analysis confirmed the classic association of P with seed weight. In common bean, white seeds are the result of convergent evolution and, among plant species, orthologous convergence on a single transcription factor gene was observed.
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http://dx.doi.org/10.1111/nph.15259DOI Listing
August 2018

Piperlongumine potentiates the effects of gemcitabine in and human pancreatic cancer models.

Oncotarget 2018 Feb 23;9(12):10457-10469. Epub 2017 Dec 23.

Department of Biological Sciences, North Dakota State University, Fargo, ND 51808, USA.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers due to a late diagnosis and poor response to available treatments. There is a need to identify complementary treatment strategies that will enhance the efficacy and reduce the toxicity of currently used therapeutic approaches. We investigated the ability of a known ROS inducer, piperlongumine (PL), to complement the modest anti-cancer effects of the approved chemotherapeutic agent gemcitabine (GEM) in PDAC cells and . PDAC cells treated with PL + GEM showed reduced cell viability, clonogenic survival, and growth on Matrigel compared to control and individually-treated cells. Nude mice bearing orthotopically implanted MIA PaCa-2 cells treated with both PL (5 mg/kg) and GEM (25 mg/kg) had significantly lower tumor weight and volume compared to control and single agent-treated mice. RNA sequencing (RNA-Seq) revealed that PL + GEM resulted in significant changes in p53-responsive genes that play a role in cell death, cell cycle, oxidative stress, and DNA repair pathways. Cell culture assays confirmed PL + GEM results in elevated ROS levels, arrests the cell cycle in the G0/G1 phase, and induces PDAC cell death. We propose a mechanism for the complementary anti-tumor effects of PL and GEM in PDAC cells through elevation of ROS and transcription of cell cycle arrest and cell death-associated genes. Collectively, our results suggest that PL has potential to be combined with GEM to more effectively treat PDAC.
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http://dx.doi.org/10.18632/oncotarget.23623DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5828188PMC
February 2018

Genetic Architecture of Dietary Fiber and Oligosaccharide Content in a Middle American Panel of Edible Dry Bean.

Plant Genome 2018 03;11(1)

Common bean ( L.) is the most consumed edible grain legume worldwide and contains a wide range of nutrients for human health including dietary fiber. Diets high in beans are associated with lower rates of chronic diseases such as obesity and type 2 diabetes, and the content of dietary fibers varies among different market classes of dry bean. In this study, we evaluated the dietary fiber content in a Middle American diversity panel (MDP) of common bean and evaluated the genetic architecture of the various dietary fiber components. The dietary fiber components included insoluble and soluble dietary fibers as well as the antinutritional raffinose family of oligosaccharides (RFOs; raffinose, stachyose, and verbascose). All variables measured differed among market classes and entries. Colored bean seeds had higher levels of insoluble dietary fibers with the black market class showing also the highest raffinose and stachyose content. Cultivars and lines released since 1997 had higher insoluble dietary fibers and RFO content in race Durango. Higher levels of RFOs were also observed in cultivars with type II growth habit that was a recent breeding target in Durango race germplasm. Candidate genes for dietary fiber traits, especially homologs to two main genes in the RFO biosynthesis pathway, were identified. The knowledge of diversity of dietary fibers in the MDP accompanied with the identification of candidate genes could effectively improve dietary fiber components in common bean.
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http://dx.doi.org/10.3835/plantgenome2017.08.0074DOI Listing
March 2018

Flaxseed Consumption Inhibits Chemically Induced Lung Tumorigenesis and Modulates Expression of Phase II Enzymes and Inflammatory Cytokines in A/J Mice.

Cancer Prev Res (Phila) 2018 01 26;11(1):27-37. Epub 2017 Oct 26.

Department of Biological Sciences, North Dakota State University, Fargo, North Dakota.

Flaxseed consumption is associated with reduced oxidative stress and inflammation in lung injury models and has shown anticancer effects for breast and prostate tissues. However, the chemopreventive potential of flaxseed remains unexplored for lung cancer. In this study, we investigated the effect of flaxseed on tobacco smoke carcinogen (NNK)-induced lung tumorigenesis in an A/J mouse model. Mice exposed to NNK were fed a control diet or a 10% flaxseed-supplemented diet for 26 weeks. Flaxseed-fed mice showed reduced lung tumor incidence (78%) and multiplicity, with an average of 2.7 ± 2.3 surface lung tumor nodules and 1.0 ± 0.9 H&E cross-section nodules per lung compared with the control group, which had 100% tumor incidence and an average of 10.2 ± 5.7 surface lung tumor nodules and 3.9 ± 2.6 H&E cross-section nodules per lung. Furthermore, flaxseed-fed mice had a lower incidence of adenocarcinomas compared with control-fed mice. Western blotting performed on normal lung tissues showed flaxseed suppressed phosphorylation (activation) of p-AKT, p-ERK, and p-JNK kinases. RNA-Seq data obtained from normal lung and lung tumors of control and flaxseed-fed mice suggested that flaxseed intake resulted in differential expression of genes involved in inflammation-mediated cytokine signaling (, and ), xenobiotic metabolism (several , and ), and signaling pathways (AKT and MAPK) involved in tumor cell proliferation. Together, our results indicate that dietary flaxseed supplementation may be an effective chemoprevention strategy for chemically induced lung carcinogenesis by altering signaling pathways, inflammation, and oxidative stress. .
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http://dx.doi.org/10.1158/1940-6207.CAPR-17-0119DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5754250PMC
January 2018

Genetic Architecture of Flooding Tolerance in the Dry Bean Middle-American Diversity Panel.

Front Plant Sci 2017 6;8:1183. Epub 2017 Jul 6.

Department of Plant Sciences, North Dakota State UniversityFargo, ND, United States.

Flooding is a devastating abiotic stress that endangers crop production in the twenty-first century. Because of the severe susceptibility of common bean ( L.) to flooding, an understanding of the genetic architecture and physiological responses of this crop will set the stage for further improvement. However, challenging phenotyping methods hinder a large-scale genetic study of flooding tolerance in common bean and other economically important crops. A greenhouse phenotyping protocol was developed to evaluate the flooding conditions at early stages. The Middle-American diversity panel ( = 272) of common bean was developed to capture most of the diversity exits in North American germplasm. This panel was evaluated for seven traits under both flooded and non-flooded conditions at two early developmental stages. A subset of contrasting genotypes was further evaluated in the field to assess the relationship between greenhouse and field data under flooding condition. A genome-wide association study using ~150 K SNPs was performed to discover genomic regions associated with multiple physiological responses. The results indicate a significant strong correlation ( > 0.77) between greenhouse and field data, highlighting the reliability of greenhouse phenotyping method. Black and small red beans were the least affected by excess water at germination stage. At the seedling stage, pinto and great northern genotypes were the most tolerant. Root weight reduction due to flooding was greatest in pink and small red cultivars. Flooding reduced the chlorophyll content to the greatest extent in the navy bean cultivars compared with other market classes. Races of Durango/Jalisco and Mesoamerica were separated by both genotypic and phenotypic data indicating the potential effect of eco-geographical variations. Furthermore, several loci were identified that potentially represent the antagonistic pleiotropy. The GWAS analysis revealed peaks at Pv08/1.6 Mb and Pv02/41 Mb that are associated with root weight and germination rate, respectively. These regions are syntenic with two QTL reported in soybean ( L.) that contribute to flooding tolerance, suggesting a conserved evolutionary pathway involved in flooding tolerance for these related legumes.
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http://dx.doi.org/10.3389/fpls.2017.01183DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5498472PMC
July 2017

Enterolactone Induces G-phase Cell Cycle Arrest in Nonsmall Cell Lung Cancer Cells by Downregulating Cyclins and Cyclin-dependent Kinases.

Nutr Cancer 2017 May-Jun;69(4):652-662. Epub 2017 Mar 21.

a Department of Biological Sciences , North Dakota State University , Fargo , North Dakota , USA.

Flaxseed is a rich source of the plant lignan secoisolariciresinol diglucoside (SDG), which is metabolized into mammalian lignans enterodiol (ED) and enterolactone (EL) in the digestive tract. The anticancer properties of these lignans have been demonstrated for various cancer types, but have not been studied for lung cancer. In this study, we investigated the anticancer effects of EL for several nonsmall cell lung cancer (NSCLC) cell lines of various genetic backgrounds. EL inhibited the growth of A549, H441, and H520 lung cancer cells in concentration- and time-dependent manners. The antiproliferative effects of EL for lung cancer cells were not due to enhanced cell death, but rather due to G-phase cell cycle arrest. Molecular studies revealed that EL decreased mRNA or protein expression levels of the G-phase promoters cyclin D1, cyclin E, cyclin-dependent kinases (CDK)-2, -4, and -6, and p-cdc25A; decreased phosphorylated retinoblastoma (p-pRb) protein levels; and simultaneously increased levels of p21, a negative regulator of the G phase. The results suggest that EL inhibits the growth of NSCLC cell lines by downregulating G-phase cyclins and CDKs, and upregulating p21, which leads to G-phase cell cycle arrest. Therefore, EL may hold promise as an adjuvant treatment for lung cancer therapy.
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http://dx.doi.org/10.1080/01635581.2017.1296169DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5500210PMC
June 2017

Genome-Wide Association Study Identifies Candidate Loci Underlying Agronomic Traits in a Middle American Diversity Panel of Common Bean.

Plant Genome 2016 11;9(3)

Common bean ( L.) breeding programs aim to improve both agronomic and seed characteristics traits. However, the genetic architecture of the many traits that affect common bean production are not completely understood. Genome-wide association studies (GWAS) provide an experimental approach to identify genomic regions where important candidate genes are located. A panel of 280 modern bean genotypes from race Mesoamerica, referred to as the Middle American Diversity Panel (MDP), were grown in four US locations, and a GWAS using >150,000 single-nucleotide polymorphisms (SNPs) (minor allele frequency [MAF] ≥ 5%) was conducted for six agronomic traits. The degree of inter- and intrachromosomal linkage disequilibrium (LD) was estimated after accounting for population structure and relatedness. The LD varied between chromosomes for the entire MDP and among race Mesoamerica and Durango-Jalisco genotypes within the panel. The LD patterns reflected the breeding history of common bean. Genome-wide association studies led to the discovery of new and known genomic regions affecting the agronomic traits at the entire population, race, and location levels. We observed strong colocalized signals in a narrow genomic interval for three interrelated traits: growth habit, lodging, and canopy height. Overall, this study detected ∼30 candidate genes based on a priori and candidate gene search strategies centered on the 100-kb region surrounding a significant SNP. These results provide a framework from which further research can begin to understand the actual genes controlling important agronomic production traits in common bean.
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http://dx.doi.org/10.3835/plantgenome2016.02.0012DOI Listing
November 2016

Sequence-Based Introgression Mapping Identifies Candidate White Mold Tolerance Genes in Common Bean.

Plant Genome 2016 07;9(2)

White mold, caused by the necrotrophic fungus (Lib.) de Bary, is a major disease of common bean ( L.). WM7.1 and WM8.3 are two quantitative trait loci (QTL) with major effects on tolerance to the pathogen. Advanced backcross populations segregating individually for either of the two QTL, and a recombinant inbred (RI) population segregating for both QTL were used to fine map and confirm the genetic location of the QTL. The QTL intervals were physically mapped using the reference common bean genome sequence, and the physical intervals for each QTL were further confirmed by sequence-based introgression mapping. Using whole-genome sequence data from susceptible and tolerant DNA pools, introgressed regions were identified as those with significantly higher numbers of single-nucleotide polymorphisms (SNPs) relative to the whole genome. By combining the QTL and SNP data, WM7.1 was located to a 660-kb region that contained 41 gene models on the proximal end of chromosome Pv07, while the WM8.3 introgression was narrowed to a 1.36-Mb region containing 70 gene models. The most polymorphic candidate gene in the WM7.1 region encodes a BEACH-domain protein associated with apoptosis. Within the WM8.3 interval, a receptor-like protein with the potential to recognize pathogen effectors was the most polymorphic gene. The use of gene and sequence-based mapping identified two candidate genes whose putative functions are consistent with the current model of pathogenicity.
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http://dx.doi.org/10.3835/plantgenome2015.09.0092DOI Listing
July 2016

Transcriptome Analysis of Piperlongumine-Treated Human Pancreatic Cancer Cells Reveals Involvement of Oxidative Stress and Endoplasmic Reticulum Stress Pathways.

J Med Food 2016 Jun 27;19(6):578-85. Epub 2016 Apr 27.

1 Department of Biological Sciences North Dakota State University , Fargo, North Dakota, USA .

Piperlongumine (PL), an alkaloid obtained from long peppers, displays antitumorigenic properties for a variety of human cell- and animal-based models. The aim of this study was to identify the underlying molecular mechanisms for PL anticancer effects on human pancreatic cancer cells. RNA sequencing (RNA-seq) was used to identify the effects of PL on the transcriptome of MIA PaCa-2 human pancreatic cancer cells. PL treatment of pancreatic cancer cells resulted in differential expression of 683 mRNA transcripts with known protein functions, 351 of which were upregulated and 332 of which were downregulated compared to control-treated cells. Transcripts associated with oxidative stress, endoplasmic reticulum (ER) stress, and unfolded protein response pathways were significantly overexpressed with PL treatment. Reverse transcription-quantitative polymerase chain reaction and western blotting were used to validate the RNA-seq results, which included upregulation of HO-1, IRE1α, cytochrome c, and ASNS. The results provide key insight into the mechanisms by which PL alters cancer cell physiology and identify that activation of oxidative stress and ER stress pathways is a critical avenue for PL anticancer effects.
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http://dx.doi.org/10.1089/jmf.2015.0152DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4904158PMC
June 2016

Genome-Wide Association Mapping for Resistance to Leaf and Stripe Rust in Winter-Habit Hexaploid Wheat Landraces.

PLoS One 2015 15;10(6):e0129580. Epub 2015 Jun 15.

Department of Plant Pathology, North Dakota State University, Fargo, North Dakota, United States of America.

Leaf rust, caused by Puccinia triticina (Pt), and stripe rust, caused by P. striiformis f. sp. tritici (Pst), are destructive foliar diseases of wheat worldwide. Breeding for disease resistance is the preferred strategy of managing both diseases. The continued emergence of new races of Pt and Pst requires a constant search for new sources of resistance. Here we report a genome-wide association analysis of 567 winter wheat (Triticum aestivum) landrace accessions using the Infinium iSelect 9K wheat SNP array to identify loci associated with seedling resistance to five races of Pt (MDCL, MFPS, THBL, TDBG, and TBDJ) and one race of Pst (PSTv-37) frequently found in the Northern Great Plains of the United States. Mixed linear models identified 65 and eight significant markers associated with leaf rust and stripe rust, respectively. Further, we identified 31 and three QTL associated with resistance to Pt and Pst, respectively. Eleven QTL, identified on chromosomes 3A, 4A, 5A, and 6D, are previously unknown for leaf rust resistance in T. aestivum.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0129580PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4468153PMC
April 2016

Association mapping of seedling resistance to spot form net blotch in a worldwide collection of barley.

Phytopathology 2015 Apr;105(4):500-8

First, second, fourth, and fifth authors: Department of Plant Pathology, North Dakota State University, Fargo, ND 58108-6050; third author: Department of Plant Science, North Dakota State University, Fargo, ND 58108-6050; and fourth author: U.S. Department of Agriculture-Agriculture Research Service, Red River Valley Agricultural Research Center, Cereal Crops Research Unit, Fargo, ND 58102-2765.

Spot form net blotch (SFNB), caused by the necrotrophic fungal pathogen Pyrenophora teres f. maculata, is an important foliar disease of barley in major production regions around the world. Deployment of adequate host resistance is challenging because the virulence of P. teres f. maculata is highly variable and characterized minor-effect resistances are typically ineffective against the diverse pathogen populations. A world barley core collection consisting of 2,062 barley accessions of diverse origin and genotype were phenotyped at the seedling stage with four P. teres f. maculata isolates collected from the United States (FGO), New Zealand (NZKF2), Australia (SG1), and Denmark (DEN 2.6). Of the 2,062 barley accessions phenotyped, 1,480 were genotyped with the Illumina barley iSelect chip and passed the quality controls with 5,954 polymorphic markers used for further association mapping analysis. Genome-wide association mapping was utilized to identify and map resistance loci from the seedling disease response data and the single nucleotide polymorphism (SNP) marker data. The best among six different regression models was identified for each isolate and association analysis was performed separately for each. A total of 138 significant (-log10P value>3.0) marker-trait associations (MTA) were detected. Using a 5 cM cutoff, a total of 10, 8, 13, and 10 quantitative trait loci (QTL) associated with SFNB resistance were identified for the FGO, SG1, NZKF2, and DEN 2.6 isolates, respectively. Loci containing from 1 to 34 MTA were identified on all seven barley chromosomes with one locus at 66 to 69 cM on chromosome 2H common to all four isolates. Six distinct loci were identified by the association mapping (AM) analysis that corresponded to previously characterized SFNB resistance QTL identified by biparental population analysis (QRpt4, QRpt6, Rpt4, Rpt6, Rpt7, and a QTL on 4H that was not given a provisional gene or QTL nomenclature). The 21 putative novel loci identified may represent a broad spectrum of resistance and or susceptibility loci. This is the first comprehensive AM study to characterize SFNB resistance loci underlying broad populations of the barley host and P. teres f. maculata pathogen.
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http://dx.doi.org/10.1094/PHYTO-04-14-0106-RDOI Listing
April 2015

Genome-wide association study reveals novel quantitative trait Loci associated with resistance to multiple leaf spot diseases of spring wheat.

PLoS One 2014 30;9(9):e108179. Epub 2014 Sep 30.

Center for Integrated Pest Management and Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America.

Accelerated wheat development and deployment of high-yielding, climate resilient, and disease resistant cultivars can contribute to enhanced food security and sustainable intensification. To facilitate gene discovery, we assembled an association mapping panel of 528 spring wheat landraces of diverse geographic origin for a genome-wide association study (GWAS). All accessions were genotyped using an Illumina Infinium 9K wheat single nucleotide polymorphism (SNP) chip and 4781 polymorphic SNPs were used for analysis. To identify loci underlying resistance to the major leaf spot diseases and to better understand the genomic patterns, we quantified population structure, allelic diversity, and linkage disequilibrium. Our results showed 32 loci were significantly associated with resistance to the major leaf spot diseases. Further analysis identified QTL effective against major leaf spot diseases of wheat which appeared to be novel and others that were previously identified by association analysis using Diversity Arrays Technology (DArT) and bi-parental mapping. In addition, several identified SNPs co-localized with genes that have been implicated in plant disease resistance. Future work could aim to select the putative novel loci and pyramid them in locally adapted wheat cultivars to develop broad-spectrum resistance to multiple leaf spot diseases of wheat via marker-assisted selection (MAS).
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0108179PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4182470PMC
June 2015

Genome-wide association studies identifies seven major regions responsible for iron deficiency chlorosis in soybean (Glycine max).

PLoS One 2014 16;9(9):e107469. Epub 2014 Sep 16.

Genomics and Bioinformatics Program, North Dakota State University, Fargo, North Dakota, United States of America; Department of Plant Sciences, North Dakota State University, Fargo, North Dakota, United States of America.

Iron deficiency chlorosis (IDC) is a yield limiting problem in soybean (Glycine max (L.) Merr) production regions with calcareous soils. Genome-wide association study (GWAS) was performed using a high density SNP map to discover significant markers, QTL and candidate genes associated with IDC trait variation. A stepwise regression model included eight markers after considering LD between markers, and identified seven major effect QTL on seven chromosomes. Twelve candidate genes known to be associated with iron metabolism mapped near these QTL supporting the polygenic nature of IDC. A non-synonymous substitution with the highest significance in a major QTL region suggests soybean orthologs of FRE1 on Gm03 is a major gene responsible for trait variation. NAS3, a gene that encodes the enzyme nicotianamine synthase which synthesizes the iron chelator nicotianamine also maps to the same QTL region. Disease resistant genes also map to the major QTL, supporting the hypothesis that pathogens compete with the plant for Fe and increase iron deficiency. The markers and the allelic combinations identified here can be further used for marker assisted selection.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0107469PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4166409PMC
June 2015

A reference genome for common bean and genome-wide analysis of dual domestications.

Nat Genet 2014 Jul 8;46(7):707-13. Epub 2014 Jun 8.

Vegetable and Forage Crop Research Unit, US Department of Agriculture-Agricultural Research Service, Prosser, Washington, USA.

Common bean (Phaseolus vulgaris L.) is the most important grain legume for human consumption and has a role in sustainable agriculture owing to its ability to fix atmospheric nitrogen. We assembled 473 Mb of the 587-Mb genome and genetically anchored 98% of this sequence in 11 chromosome-scale pseudomolecules. We compared the genome for the common bean against the soybean genome to find changes in soybean resulting from polyploidy. Using resequencing of 60 wild individuals and 100 landraces from the genetically differentiated Mesoamerican and Andean gene pools, we confirmed 2 independent domestications from genetic pools that diverged before human colonization. Less than 10% of the 74 Mb of sequence putatively involved in domestication was shared by the two domestication events. We identified a set of genes linked with increased leaf and seed size and combined these results with quantitative trait locus data from Mesoamerican cultivars. Genes affected by domestication may be useful for genomics-enabled crop improvement.
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http://dx.doi.org/10.1038/ng.3008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7048698PMC
July 2014

Genetic diversity and population structure among pea (Pisum sativum L.) cultivars as revealed by simple sequence repeat and novel genic markers.

Mol Biotechnol 2014 Oct;56(10):925-38

Department of Plant Sciences, North Dakota State University, Fargo, ND, 58108, USA.

Field pea (Pisum sativum L.) is an important cool season legume crop widely grown around the world. This research provides a basis for selection of pea germplasm across geographical regions in current and future breeding and genetic mapping efforts for pea improvement. Eleven novel genic markers were developed from pea expressed sequence tag (EST) sequences having significant similarity with gene calls from Medicago truncatula spanning at least one intron. In this study, 96 cultivars widely grown or used in breeding programs in the USA and Canada were analyzed for genetic diversity using 31 microsatellite or simple sequence repeat (SSR) and 11 novel EST-derived genic markers. The polymorphic information content varied from 0.01-0.56 among SSR markers and 0.04-0.43 among genic markers. The results showed that SSR and EST-derived genic markers displayed one or more highly reproducible, multi-allelic, and easy to score loci ranging from 200 to 700 bp in size. Genetic diversity was assessed through unweighted neighbor-joining method, and 96 varieties were grouped into three main clusters based on the dissimilarity matrix. Four subpopulations were determined through STRUCTURE analysis with no significant geographic separation of the subpopulations. The findings of the present study can be used to select diverse genotypes to be used as parents of crosses aimed for breeding improved pea cultivars.
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http://dx.doi.org/10.1007/s12033-014-9772-yDOI Listing
October 2014

Developing market class specific InDel markers from next generation sequence data in Phaseolus vulgaris L.

Front Plant Sci 2014 13;5:185. Epub 2014 May 13.

Genomics and Bioinformatics Program, North Dakota State University Fargo, ND, USA ; Department of Plant Sciences, North Dakota State University Fargo, ND, USA.

Next generation sequence data provides valuable information and tools for genetic and genomic research and offers new insights useful for marker development. This data is useful for the design of accurate and user-friendly molecular tools. Common bean (Phaseolus vulgaris L.) is a diverse crop in which separate domestication events happened in each gene pool followed by race and market class diversification that has resulted in different morphological characteristics in each commercial market class. This has led to essentially independent breeding programs within each market class which in turn has resulted in limited within market class sequence variation. Sequence data from selected genotypes of five bean market classes (pinto, black, navy, and light and dark red kidney) were used to develop InDel-based markers specific to each market class. Design of the InDel markers was conducted through a combination of assembly, alignment and primer design software using 1.6× to 5.1× coverage of Illumina GAII sequence data for each of the selected genotypes. The procedure we developed for primer design is fast, accurate, less error prone, and higher throughput than when they are designed manually. All InDel markers are easy to run and score with no need for PCR optimization. A total of 2687 InDel markers distributed across the genome were developed. To highlight their usefulness, they were employed to construct a phylogenetic tree and a genetic map, showing that InDel markers are reliable, simple, and accurate.
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http://dx.doi.org/10.3389/fpls.2014.00185DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4026720PMC
May 2014

Population structure and linkage disequilibrium in Lupinus albus L. germplasm and its implication for association mapping.

Theor Appl Genet 2012 Aug 28;125(3):517-30. Epub 2012 Mar 28.

Department of Plant Sciences, North Dakota State University, Fargo, ND 58108, USA.

White lupin (Lupinus albus L.) has been around since 300 B.C. and is recognized for its ability to grow on poor soils and application as green manure in addition to seed harvest. The seed has very high levels of protein (33-47 %) and oil (6-13 %). It also has many secondary metabolites that are potentially of nutraceutical value to animals and humans. Despite such a great potential, lupins role in modern agriculture began only in the twentieth century. Although a large collection of Lupinus germplasm accessions is available worldwide, rarely have they been genetically characterized. Additionally, scarce genomic resources in terms of recombinant populations and genome information have been generated for L. albus. With the advancement in association mapping methods, the natural populations have the potential to replace the recombinant populations in gene mapping and marker-trait associations. Therefore, we studied the genetic similarity, population structure and marker-trait association in a USDA germplasm collection for their current and future application in this crop improvement. A total of 122 PI (Plant Inventory) lines were screened with 18 AFLP primer pairs that generated 2,277 fragments. A subset of 892 polymorphic markers with MAF >0.05 (minor allele frequency) were used for association mapping. The cluster analysis failed to group accessions on the basis of their passport information, and a weak structure and low linkage disequilibrium (LD) were observed indicating the usefulness of the collection for association mapping. Moreover, we were also able to identify two markers (a p value of 1.53 × 10(-4) and 2.3 × 10(-4)) that explained 22.69 and 20.5 % of seed weight variation determined using R (LR) (2) . The implications of lack of geographic clustering, population structure, low LD and the ability of AFLP to map seed weight trait using association mapping and the usefulness of the PI collections in breeding programs are discussed.
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http://dx.doi.org/10.1007/s00122-012-1850-6DOI Listing
August 2012

Mixed model association mapping for fusarium head blight resistance in tunisian-derived durum wheat populations.

G3 (Bethesda) 2011 Aug 1;1(3):209-18. Epub 2011 Aug 1.

Sources of resistance to Fusarium head blight (FHB) in wheat are mostly restricted to Chinese hexaploid genotypes. The effort to incorporate the resistance from hexaploid wheat or wild relatives to cultivated durum wheat (Triticum turgidum L. var. durum Desf.) have not been successful in providing resistance to the level of the donor parents. In this study, we used 171 BC(1)F(6) and 169 BC(1)F(7) lines derived from crossing of four Tunisian tetraploid sources of resistance (Tun7, Tun18, Tun34, Tun36) with durum cultivars 'Ben,' 'Maier,' 'Lebsock,' and 'Mountrail' for association studies. The Tun18 and Tun7 FHB resistances were found to be comparable to the best hexaploid wheat sources. A new significant QTL for FHB resistance was identified on the long arm of chromosome 5B (Qfhs.ndsu-5BL) with both association and classical QTL mapping analysis. Linkage disequilibrium (LD) blocks extending up to 40 cM were evident in these populations. The linear mixed model considering the structure (Q or P) and the kinship matrix (K(T)) estimated by restricted maximum likelihood (REML) was identified as the best for association studies in a mixture of wheat populations from a breeding program. The results of association mapping analysis also demonstrated a region on the short arm of chromosome 3B as potentially linked to FHB resistance. This region is in proximity of major FHB resistance gene fhb1 reported in hexaploid wheat. A possibility of having susceptibility or suppressor of resistance gene(s) on durum wheat chromosome 2A was further confirmed in this material, explaining the problem in developing resistant genotypes without counter selection against this region.
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http://dx.doi.org/10.1534/g3.111.000489DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3276138PMC
August 2011

Investigation of the domestication of common bean (Phaseolus vulgaris) using multilocus sequence data.

Funct Plant Biol 2011 Dec;38(12):953-967

North Dakota State University, Department of Plant Sciences, Fargo, ND 58102, USA.

Multilocus sequence data collected from domesticated and related wild relatives provides a rich source of information on the effect of human selection on the diversity and adaptability of a species to complex environments. To evaluate the domestication history of common bean (Phaseolus vulgaris L.), multilocus sequence data from landraces representing the various races within the Middle American (MA) and Andean gene pools was evaluated. Across 13 loci, nucleotide diversity was similar between landraces and wild germplasm in both gene pools. The diversity data were evaluated using the approximate Bayesian computation approach to test multiple domestication models and estimate population demographic parameters. A model with a single domestication event coupled with bidirectional migration between wild and domesticated genotypes fitted the data better than models consisting of two or three domestication events in each genepool. The effective bottleneck population size was ~50% of the base population in each genepool. The bottleneck began ~8200 and ~8500 years before present and ended at ~6300 and ~7000 years before present in MA and Andean gene pools respectively. Linkage disequilibrium decayed to a greater extent in the MA genepool. Given the (1) geographical adaptation bottleneck in each wild gene pool, (2) a subsequent domestication bottleneck within each gene pool, (3) differentiation into gene-pool specific races and (4) variable extents of linkage disequilibrium, association mapping experiments for common bean would more appropriately be performed within each genepool.
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http://dx.doi.org/10.1071/FP11124DOI Listing
December 2011

Syntenic relationships among legumes revealed using a gene-based genetic linkage map of common bean (Phaseolus vulgaris L.).

Theor Appl Genet 2010 Oct 6;121(6):1103-16. Epub 2010 Jul 6.

Genomics and Bioinformatics Program, North Dakota State University, Fargo, ND 58105, USA.

Molecular linkage maps are an important tool for gene discovery and cloning, crop improvement, further genetic studies, studies on diversity and evolutionary history, and cross-species comparisons. Linkage maps differ in both the type of marker and type of population used. In this study, gene-based markers were used for mapping in a recombinant inbred (RI) population of Phaseolus vulgaris L. P. vulgaris, common dry bean, is an important food source, economic product, and model organism for the legumes. Gene-based markers were developed that corresponded to genes controlling mutant phenotypes in Arabidopsis thaliana, genes undergoing selection during domestication in maize, and genes that function in a biochemical pathway in A. thaliana. Sequence information, including introns and 3' UTR, was generated for over 550 genes in the two genotypes of P. vulgaris. Over 1,800 single nucleotide polymorphisms and indels were found, 300 of which were screened in the RI population. The resulting LOD 2.0 map is 1,545 cM in length and consists of 275 gene-based and previously mapped core markers. An additional 153 markers that mapped at LOD <1.0 were placed in genetic bins. By screening the parents of other mapping populations, it was determined that the markers were useful for other common Mesoamerican × Andean mapping populations. The location of the mapped genes relative to their homologs in Arabidopsis thaliana (At), Medicago truncatula (Mt), and Lotus japonicus (Lj) were determine by using a tblastx analysis with the current psedouchromosome builds for each of the species. While only short blocks of synteny were observed with At, large-scale macrosyntenic blocks were observed with Mt and Lj. By using Mt and Lj as bridging species, the syntenic relationship between the common bean and peanut was inferred.
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http://dx.doi.org/10.1007/s00122-010-1375-9DOI Listing
October 2010

Synteny mapping between common bean and soybean reveals extensive blocks of shared loci.

BMC Genomics 2010 Mar 18;11:184. Epub 2010 Mar 18.

Genomics and Bioinformatics Program, North Dakota State University, Fargo, ND 58105, USA.

Background: Understanding syntentic relationship between two species is critical to assessing the potential for comparative genomic analysis. Common bean (Phaseolus vulgaris L.) and soybean (Glycine max L.), the two most important members of the Phaseoleae legumes, appear to have a diploid and polyploidy recent past, respectively. Determining the syntentic relationship between these two species will allow researchers to leverage not only genomic resources but also genetic data for important agronomic traits to improve both of these species.

Results: Genetically-positioned transcript loci of common bean were mapped relative to the recent soybean 1.01 pseudochromosome assembly. In nearly every case, each common bean locus mapped to two loci in soybean, a result consistent with the duplicate polyploidy history of soybean. Blocks of synteny averaging 32 cM in common bean and 4.9 Mb in soybean were observed for all 11 common bean linkage groups, and these blocks mapped to all 20 soybean pseudochromosomes. The median physical-to-genetic distance ratio in common bean (based on soybean physical distances) was approximately 120 kb/cM. approximately 15,000 common bean sequences (primarily EST contigs and EST singletons) were electronically positioned onto the common bean map using the shared syntentic blocks as references points.

Conclusion: The collected evidence from this mapping strongly supports the duplicate history of soybean. It further provides evidence that the soybean genome was fractionated and reassembled at some point following the duplication event. These well mapped syntentic relationships between common bean and soybean will enable researchers to target specific genomic regions to discover genes or loci that affect phenotypic expression in both species.
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http://dx.doi.org/10.1186/1471-2164-11-184DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851600PMC
March 2010