The Experts below are selected from a list of 33492 Experts worldwide ranked by ideXlab platform
David G. Schatz - One of the best experts on this subject based on the ideXlab platform.
-
identification of rag like transposons in protostomes suggests their ancient bilaterian origin
Mobile Dna, 2020Co-Authors: Eliza C Martin, Pierre Pontarotti, Célia Vicari, Andrei J. Petrescu, Louis Tsakoungouafo, David G. SchatzAbstract:V(D) J recombination is essential for adaptive immunity in jawed vertebrates and is initiated by the RAG1-RAG2 endonuclease. The RAG1 and RAG2 genes are thought to have evolved from a RAGL (RAG-like) transposon containing convergently-oriented RAG1-like (RAG1L) and RAG2-like (RAG2L) genes. Elements resembling this presumptive evolutionary precursor have thus far only been detected convincingly in deuterostomes, leading to the model that the RAGL transposon first appeared in an early deuterostome. We have identified numerous RAGL transposons in the genomes of protostomes, including oysters and mussels (phylum Mollusca) and a ribbon worm (phylum Nemertea), and in the genomes of several cnidarians. Phylogenetic analyses are consistent with vertical evolution of RAGL transposons within the Bilateria clade and with its presence in the bilaterian ancestor. Many of the RAGL transposons identified in protostomes are intact elements containing convergently oriented RAG1L and RAG2L genes flanked by terminal inverted repeats (TIRs) and target site duplications with striking similarities with the corresponding elements in deuterostomes. In addition, protostome genomes contain numerous intact RAG1L-RAG2L adjacent gene pairs that lack detectable flanking TIRs. Domains and critical active site and structural amino acids needed for endonuclease and transposase activity are present and conserved in many of the predicted RAG1L and RAG2L proteins encoded in protostome genomes. Active RAGL transposons were present in multiple protostome lineages and many were likely transmitted vertically during protostome evolution. It appears that RAGL transposons were broadly active during bilaterian evolution, undergoing multiple duplication and loss/fossilization events, with the RAGL genes that persist in present day protostomes perhaps constituting both active RAGL transposons and domesticated RAGL genes. Our findings raise the possibility that the RAGL transposon arose earlier in evolution than previously thought, either in an early bilaterian or prior to the divergence of bilaterians and non-bilaterians, and alter our understanding of the evolutionary history of this important group of transposons.
-
immature lymphocytes inhibit rag1 and RAG2 transcription and v d j recombination in response to dna double strand breaks
Journal of Immunology, 2017Co-Authors: David G. Schatz, Megan R Fisher, Adrian Riverareyes, Noah B Bloch, Craig H. BassingAbstract:Mammalian cells have evolved a common DNA damage response (DDR) that sustains cellular function, maintains genomic integrity, and suppresses malignant transformation. In pre-B cells, DNA double-strand breaks (DSBs) induced at Igκ loci by the Rag1/RAG2 (RAG) endonuclease engage this DDR to modulate transcription of genes that regulate lymphocyte-specific processes. We previously reported that RAG DSBs induced at one Igκ allele signal through the ataxia telangiectasia mutated (ATM) kinase to feedback-inhibit RAG expression and RAG cleavage of the other Igκ allele. In this article, we show that DSBs induced by ionizing radiation, etoposide, or bleomycin suppress Rag1 and RAG2 mRNA levels in primary pre-B cells, pro-B cells, and pro-T cells, indicating that inhibition of Rag1 and RAG2 expression is a prevalent DSB response among immature lymphocytes. DSBs induced in pre-B cells signal rapid transcriptional repression of Rag1 and RAG2 , causing downregulation of both Rag1 and RAG2 mRNA, but only Rag1 protein. This transcriptional inhibition requires the ATM kinase and the NF-κB essential modulator protein, implicating a role for ATM-mediated activation of canonical NF-κB transcription factors. Finally, we demonstrate that DSBs induced in pre-B cells by etoposide or bleomycin inhibit recombination of Igκ loci and a chromosomally integrated substrate. Our data indicate that immature lymphocytes exploit a common DDR signaling pathway to limit DSBs at multiple genomic locations within developmental stages wherein monoallelic Ag receptor locus recombination is enforced. We discuss the implications of our findings for mechanisms that orchestrate the differentiation of monospecific lymphocytes while suppressing oncogenic Ag receptor locus translocations.
-
Collaboration of RAG2 with RAG1-like proteins during the evolution of V(D)J recombination.
Genes & development, 2016Co-Authors: Lina Marcela Carmona, Sebastian D. Fugmann, David G. SchatzAbstract:The recombination-activating gene 1 (RAG1) and RAG2 proteins initiate V(D)J recombination, the process that assembles the B- and T-lymphocyte antigen receptor genes of jawed vertebrates. RAG1 and RAG2 are thought to have arisen from a transposable element, but the origins of this element are not understood. We show that two ancestral RAG1 proteins, Transib transposase and purple sea urchin RAG1-like, have a latent ability to initiate V(D)J recombination when coexpressed with RAG2 and that in vitro transposition by Transib transposase is stimulated by RAG2. Conversely, we report low levels of V(D)J recombination by RAG1 in the absence of RAG2. Recombination by RAG1 alone differs from canonical V(D)J recombination in having lost the requirement for asymmetric DNA substrates, implicating RAG2 in the origins of the "12/23 rule," a fundamental regulatory feature of the reaction. We propose that evolution of RAG1/RAG2 began with a Transib transposon whose intrinsic recombination activity was enhanced by capture of an ancestral RAG2, allowing for the development of adaptive immunity.
-
Recruitment of RAG1 and RAG2 to Chromatinized DNA during V(D)J Recombination
Molecular and cellular biology, 2015Co-Authors: Keerthi Shetty, David G. SchatzAbstract:V(D)J recombination is initiated by the binding of the RAG1 and RAG2 proteins to recombination signal sequences (RSSs) that consist of conserved heptamer and nonamer sequences separated by a spacer of either 12 or 23 bp. Here, we used RAG-inducible pro-B v-Abl cell lines in conjunction with chromatin immunoprecipitation to better understand the protein and RSS requirements for RAG recruitment to chromatin. Using a catalytic mutant form of RAG1 to prevent recombination, we did not observe cooperation between RAG1 and RAG2 in their recruitment to endogenous Jκ gene segments over a 48-h time course. Using retroviral recombination substrates, we found that RAG1 was recruited inefficiently to substrates lacking an RSS or containing a single RSS, better to substrates with two 12-bp RSSs (12RSSs) or two 23-bp RSSs (23RSSs), and more efficiently to a substrate with a 12/23RSS pair. RSS mutagenesis demonstrated a major role for the nonamer element in RAG1 binding, and correspondingly, a cryptic RSS consisting of a repeat of CA dinucleotides, which poorly re-creates the nonamer, was ineffective in recruiting RAG1. Our findings suggest that 12RSS-23RSS cooperation (the "12/23 rule") is important not only for regulating RAG-mediated DNA cleavage but also for the efficiency of RAG recruitment to chromatin.
-
Mapping and Quantitation of the Interaction between the Recombination Activating Gene Proteins RAG1 and RAG2
The Journal of biological chemistry, 2015Co-Authors: Yuhang Zhang, Keerthi Shetty, Marius D. Surleac, Andrei J. Petrescu, David G. SchatzAbstract:Abstract The RAG endonuclease consists of RAG1, which contains the active site for DNA cleavage, and RAG2, an accessory factor whose interaction with RAG1 is critical for catalytic function. How RAG2 activates RAG1 is not understood. Here, we used biolayer interferometry and pulldown assays to identify regions of RAG1 necessary for interaction with RAG2 and to measure the RAG1-RAG2 binding affinity (KD ∼0.4 μm) (where RAG1 and RAG2 are recombination activating genes 1 or 2). Using the Hermes transposase as a guide, we constructed a 36-kDa “mini” RAG1 capable of interacting robustly with RAG2. Mini-RAG1 consists primarily of the catalytic center and the residues N-terminal to it, but it lacks a zinc finger region in RAG1 previously implicated in binding RAG2. The ability of Mini-RAG1 to interact with RAG2 depends on a predicted α-helix (amino acids 997–1008) near the RAG1 C terminus and a region of RAG1 from amino acids 479 to 559. Two adjacent acidic amino acids in this region (Asp-546 and Glu-547) are important for both the RAG1-RAG2 interaction and recombination activity, with Asp-546 of particular importance. Structural modeling of Mini-RAG1 suggests that Asp-546/Glu-547 lie near the predicted 997-1008 α-helix and components of the active site, raising the possibility that RAG2 binding alters the structure of the RAG1 active site. Quantitative Western blotting allowed us to estimate that mouse thymocytes contain on average ∼1,800 monomers of RAG1 and ∼15,000 molecules of RAG2, implying that nuclear concentrations of RAG1 and RAG2 are below the KD value for their interaction, which could help limit off-target RAG activity.
Glen L Hartman - One of the best experts on this subject based on the ideXlab platform.
-
characterization and genetics of multiple soybean aphid biotype resistance in five soybean plant introductions
Theoretical and Applied Genetics, 2017Co-Authors: Curtis B Hill, Derek Shiao, Glen L HartmanAbstract:Key message Five soybean plant introductions expressed antibiosis resistance to multiple soybean aphid biotypes. Two introductions had resistance genes located in the Rag1, RAG2, and Rag3 regions; one introduction had resistance genes located in the Rag1, RAG2, and rag4 regions; one introduction had resistance genes located in the Rag1 and RAG2 regions; and one introduction had a resistance gene located in the RAG2 region.
-
differential reactions of soybean isolines with combinations of aphid resistance genes rag1 RAG2 and rag3 to four soybean aphid biotypes
Journal of Economic Entomology, 2016Co-Authors: Olutoyosi O Ajayioyetunde, Curtis B Hill, Ursula Reutercarlson, Doris Lagoskutz, Carl A. Bradley, Brian W Diers, Glen L HartmanAbstract:With the discovery of the soybean aphid ( Aphis glycines Matsumura) as a devastating insect pest of soybean ( Glycine max (L.) Merr.) in the United States, host resistance was recognized as an important management option. However, the identification of soybean aphid isolates exhibiting strong virulence against aphid resistance genes ( Rag genes) has highlighted the need for pyramiding genes to help ensure the durability of host resistance as a control strategy. In this study, soybean isolines with all possible combinations of the resistance and susceptibility alleles at Rag1 , RAG2 , and Rag3 were evaluated for their effectiveness against the four characterized soybean aphid biotypes. All soybean isolines, including the susceptible check carrying none of the resistance alleles (S1/S2/S3), were infested with each biotype in no-choice greenhouse tests, and the aphid populations developed on each isoline were enumerated 14 d after infestation. All gene combinations, with the exception of Rag3 alone, provided excellent protection against biotype 1. Isolines with RAG2 alone or in combination with Rag1 and Rag3 had greater levels of resistance to biotype 2 than those with either Rag1 alone, Rag3 alone, or the Rag1/3 pyramid. For biotype 3, the Rag1/3 and Rag1/2/3 pyramided lines significantly reduced aphid populations compared with all other gene combinations, while the Rag1/2/3 pyramid provided the greatest protection against biotype 4. Overall, the Rag1/2/3 pyramided line conferred the greatest protection against all four biotypes.
-
identification and molecular mapping of two soybean aphid resistance genes in soybean pi 587732
Theoretical and Applied Genetics, 2014Co-Authors: Anitha Chirumamilla, Curtis B Hill, Glen L Hartman, Brian W DiersAbstract:Soybean [Glycine max (L.) Merr.] continues to be plagued by the soybean aphid (Aphis glycines Matsumura: SA) in North America. New soybean resistance sources are needed to combat the four identified SA biotypes. The objectives of this study were to determine the inheritance of SA resistance in PI 587732 and to map resistance gene(s). For this study, 323 F2 and 214 F3 plants developed from crossing PI 587732 to two susceptible genotypes were challenged with three SA biotypes and evaluated with genetic markers. Choice tests showed that resistance to SA Biotype 1 in the first F2 population was controlled by a gene in the Rag1 region on chromosome 7, while resistance to SA Biotype 2 in the second population was controlled by a gene in the RAG2 region on chromosome 13. When 134 F3 plants segregating in both the Rag1 and RAG2 regions were tested with a 1:1 mixture of SA Biotypes 1 and 2, the RAG2 region and an interaction between the Rag1 and RAG2 regions were significantly associated with the resistance. Based on the results of the non-choice tests, the resistance gene in the Rag1 region in PI 587732 may be a different allele or gene from Rag1 from Dowling because the PI 587732 gene showed antibiosis type resistance to SA Biotype 2 while Rag1 from Dowling did not. The two SA resistance loci and genetic marker information from this study will be useful in increasing diversity of SA resistance sources and marker-assisted selection for soybean breeding programs.
Martin Gellert - One of the best experts on this subject based on the ideXlab platform.
-
crystal structure of the v d j recombinase rag1 RAG2
Nature, 2015Co-Authors: Min Sung Kim, Mikalai Lapkouski, Wei Yang, Martin GellertAbstract:V(D)J recombination in the vertebrate immune system generates a highly diverse population of immunoglobulins and T-cell receptors by combinatorial joining of segments of coding DNA. The RAG1-RAG2 protein complex initiates this site-specific recombination by cutting DNA at specific sites flanking the coding segments. Here we report the crystal structure of the mouse RAG1-RAG2 complex at 3.2 A resolution. The 230-kilodalton RAG1-RAG2 heterotetramer is 'Y-shaped', with the amino-terminal domains of the two RAG1 chains forming an intertwined stalk. Each RAG1-RAG2 heterodimer composes one arm of the 'Y', with the active site in the middle and RAG2 at its tip. The RAG1-RAG2 structure rationalizes more than 60 mutations identified in immunodeficient patients, as well as a large body of genetic and biochemical data. The architectural similarity between RAG1 and the hairpin-forming transposases Hermes and Tn5 suggests the evolutionary conservation of these DNA rearrangements.
-
initial stages of v d j recombination the organization of rag1 2 and rss dna in the postcleavage complex
Molecular Cell, 2009Co-Authors: Gabrielle J. Grundy, Martin Gellert, Emilios K. Dimitriadis, Svetlana Kotova, Christian Biertümpfel, Alasdair C. Steven, Santiago Ramonmaiques, Bernard J Heymann, Wei YangAbstract:To obtain structural information on the early stages of V(D)J recombination, we isolated a complex of the core RAG1 and RAG2 proteins with DNA containing a pair of cleaved recombination signal sequences (RSS). Stoichiometric and molecular mass analysis established that this signal-end complex (SEC) contains two protomers each of RAG1 and RAG2. Visualization of the SEC by negative-staining electron microscopy revealed an anchor-shaped particle with approximate two-fold symmetry. Consistent with a parallel arrangement of DNA and protein subunits, the N termini of RAG1 and RAG2 are positioned at opposing ends of the complex, and the DNA chains beyond the RSS nonamer emerge from the same face of the complex, near the RAG1 N termini. These first images of the V(D)J recombinase in its postcleavage state provide a framework for modeling RAG domains and their interactions with DNA.
-
Inverse transposition by the RAG1 and RAG2 proteins: role reversal of donor and target DNA.
The EMBO journal, 2002Co-Authors: I‐hung Shih, Meni Melek, Nadeesha D. Jayaratne, Martin GellertAbstract:The lymphoid-specific proteins RAG1 and RAG2 initiate V(D)J recombination by introducing DNA double-strand breaks at the recombination signal sequences (RSSs). In addition to DNA cleavage, the versatile RAG1/2 complex is capable of catalyzing several other reactions, including hybrid joint formation and the transposition of signal ends into a second DNA. Here we show that the RAG1/2 complex also mediates an unusual strand transfer reaction, inverse transposition, in which non-RSS DNA is cleaved and subsequently transferred to an RSS sequence by direct transesterification. Characterization of the reaction products and requirements suggests that inverse transposition is related to both hybrid joint formation and signal-end transposition. This aberrant activity provides another possible mechanism for some chromosomal translocations present in lymphoid tumors.
-
a stable rag1 RAG2 dna complex that is active in v d j cleavage
Cell, 1997Co-Authors: Kevin Hiom, Martin GellertAbstract:Abstract The RAG1 and RAG2 proteins initiate V(D)J recombination by making specific double-strand DNA breaks at recombination signal sequences. We show here that RAG1 and RAG2 bind specifically to this sequence, forming a stable protein–DNA complex. The complex requires the conserved heptamer and nonamer motifs of the recombination signal as well as both the RAG1 and RAG2 proteins. This complex is able to either nick or form hairpins at the V(D)J signal sequence, depending on the divalent cation present. A complex trapped using Ca 2+ is subsequently active when transferred to Mg 2+ or Mn 2+ . After cleavage, the complex is destabilized and the RAG proteins dissociate. We term this early precursor in the V(D)J recombination reaction a "stable cleavage complex."
-
the rag1 and RAG2 proteins establish the 12 23 rule in v d j recombination
Cell, 1996Co-Authors: Dik C. Van Gent, Dale A. Ramsden, Martin GellertAbstract:Abstract V(D)J recombination requires a pair of signal sequences with spacer lengths of 12 and 23 base pairs. Cleavage by the RAG1 and RAG2 proteins was previously shown to demand only a single signal sequence. Here, we establish conditions where 12- and 23-spacer signal sequences are both necessary for cleavage. Coupled cutting at both sites requires only the RAG1 and RAG2 proteins, but depends on the metal ion. In Mn 2+ , a single signal sequence supports efficient double strand cleavage, but cutting in Mg 2+ requires two signal sequences and is best with the canonical 12/23 pair. Thus, the RAG proteins determine both aspects of the specificity of V(D)J recombination, the recognition of a single signal sequence and the correct 12/23 coupling in a pair of signals.
Marjorie A. Oettinger - One of the best experts on this subject based on the ideXlab platform.
-
rag a recombinase diversified
Nature Immunology, 2009Co-Authors: Adam G. W. Matthews, Marjorie A. OettingerAbstract:To generate a diverse repertoire of antigen receptors, developing B cells and T cells undergo a complex series of DNA rearrangements collectively termed V(D)J recombination. This process is initiated by the lymphoid-specific proteins RAG1 and RAG2, which function together to generate site-specific DNA double-strand breaks that are then repaired via the classical non-homologous end-joining (NHEJ) pathway. While it is well established that RAG1-RAG2 can function as a recombinase, several recent studies have revealed that RAG1-RAG2 is actually a surprisingly multifaceted enzyme complex that plays an important role in ensuring that V(D)J recombination is faithfully executed and properly regulated in the cell. In this Review, we discuss the role of the RAG1-RAG2 complex in binding to accessible chromatin, mediating allelic pairing during V(D)J recombination, and channeling RAG-generated double-strand breaks towards the classical non-homologous end-joining (NHEJ) pathway (Fig. 1). We conclude by proposing a speculative model in which the RAG1-RAG2 recombinase functions within a specialized subnuclear compartment that we term the V(D)J recombination factory. Figure 1 Multilayered regulation of V(D)J recombination
-
rag a recombinase diversified
Nature Immunology, 2009Co-Authors: Adam G. W. Matthews, Marjorie A. OettingerAbstract:To generate a diverse repertoire of antigen receptors, developing B cells and T cells undergo a complex series of DNA rearrangements collectively termed V(D)J recombination. This process is initiated by the lymphoid-specific proteins RAG1 and RAG2, which function together to generate site-specific DNA double-strand breaks that are then repaired via the classical non-homologous end-joining (NHEJ) pathway. While it is well established that RAG1-RAG2 can function as a recombinase, several recent studies have revealed that RAG1-RAG2 is actually a surprisingly multifaceted enzyme complex that plays an important role in ensuring that V(D)J recombination is faithfully executed and properly regulated in the cell. In this Review, we discuss the role of the RAG1-RAG2 complex in binding to accessible chromatin, mediating allelic pairing during V(D)J recombination, and channeling RAG-generated double-strand breaks towards the classical non-homologous end-joining (NHEJ) pathway (Fig. 1). We conclude by proposing a speculative model in which the RAG1-RAG2 recombinase functions within a specialized subnuclear compartment that we term the V(D)J recombination factory. Figure 1 Multilayered regulation of V(D)J recombination
-
assembly of the rag1 RAG2 synaptic complex
Molecular and Cellular Biology, 2002Co-Authors: Cynthia L. Mundy, Adam G. W. Matthews, Nadja Patenge, Marjorie A. OettingerAbstract:Assembly of antigen receptor genes by V(D)J recombination requires the site-specific recognition of two distinct DNA elements differing in the length of the spacer DNA that separates two conserved recognition motifs. Under appropriate conditions, V(D)J cleavage by the purified RAG1/RAG2 recombinase is similarly restricted. Double-strand breakage occurs only when these proteins are bound to a pair of complementary signals in a synaptic complex. We examine here the binding of the RAG proteins to signal sequences and find that the full complement of proteins required for synapsis of two signals and coupled cleavage can assemble on a single signal. This complex, composed of a dimer of RAG2 and at least a trimer of RAG1, remains inactive for double-strand break formation until a second complementary signal is provided. Thus, binding of the second signal activates the complex, possibly by inducing a conformational change. If synaptic complexes are formed similarly in vivo, one signal of a recombining pair may be the preferred site for RAG1/RAG2 assembly.
-
Distinct Roles of RAG1 and RAG2 in Binding the V(D)J Recombination Signal Sequences
Molecular and Cellular Biology, 1998Co-Authors: Yoshiko Akamatsu, Marjorie A. OettingerAbstract:The RAG1 and RAG2 proteins initiate V(D)J recombination by introducing double-strand breaks at the border between a recombination signal sequence (RSS) and a coding segment. To understand the distinct functions of RAG1 and RAG2 in signal recognition, we have compared the DNA binding activities of RAG1 alone and RAG1 plus RAG2 by gel retardation and footprinting analyses. RAG1 exhibits only a three- to fivefold preference for binding DNA containing an RSS over random sequence DNA. Although direct binding of RAG2 by itself was not detected, the presence of both RAG1 and RAG2 results in the formation of a RAG1-RAG2-DNA complex which is more stable and more specific than the RAG1-DNA complex and is active in V(D)J cleavage. These results suggest that biologically effective discrimination between an RSS and nonspecific sequences requires both RAG1 and RAG2. Unlike the binding of RAG1 plus RAG2, RAG1 can bind to DNA in the absence of a divalent metal ion and does not require the presence of coding flank sequence. Footprinting of the RAG1-RAG2 complex with 1,10-phenanthroline-copper and dimethyl sulfate protection reveal that both the heptamer and the nonamer are involved. The nonamer is protected, with extensive protein contacts within the minor groove. Conversely, the heptamer is rendered more accessible to chemical attack, suggesting that binding of RAG1 plus RAG2 distorts the DNA near the coding/signal border.
-
Regions of RAG1 protein critical for V(D)J recombination.
European journal of immunology, 1996Co-Authors: Susan A. Kirch, Priya Sudarsanam, Marjorie A. OettingerAbstract:The products of the recombination activating genes RAG1 and RAG2 are essential for activating V(D)J recombination, and thus are indispensable for the production of functional and diverse antigen receptors. To investigate the function of RAG1, we have tested a series of insertion and substitution mutations for their ability to induce V(D)J rearrangement on both deletional and inversional plasmid substrates. With these substrates we were also able to assess the effects of these mutations on both coding and signal joint formation, and to show that any one mutant affected all these reactions similarly. As defined previously, the core active regions of RAG1 and RAG2 permit the deletion of 40% and 25%, respectively, of well-conserved sequence. We show here that this “dispensable” region of RAG1 is not necessary for coding joint formation or for recombination of an integrated substrate, and that this portion is not functionally redundant with the “dispensable” region of RAG2. Recombination with these core regions is also still subject to the 12/23 joining rule. Further, the minimal essential core region of RAG1 can be located within an even smaller portion of the gene.
Curtis B Hill - One of the best experts on this subject based on the ideXlab platform.
-
characterization and genetics of multiple soybean aphid biotype resistance in five soybean plant introductions
Theoretical and Applied Genetics, 2017Co-Authors: Curtis B Hill, Derek Shiao, Glen L HartmanAbstract:Key message Five soybean plant introductions expressed antibiosis resistance to multiple soybean aphid biotypes. Two introductions had resistance genes located in the Rag1, RAG2, and Rag3 regions; one introduction had resistance genes located in the Rag1, RAG2, and rag4 regions; one introduction had resistance genes located in the Rag1 and RAG2 regions; and one introduction had a resistance gene located in the RAG2 region.
-
differential reactions of soybean isolines with combinations of aphid resistance genes rag1 RAG2 and rag3 to four soybean aphid biotypes
Journal of Economic Entomology, 2016Co-Authors: Olutoyosi O Ajayioyetunde, Curtis B Hill, Ursula Reutercarlson, Doris Lagoskutz, Carl A. Bradley, Brian W Diers, Glen L HartmanAbstract:With the discovery of the soybean aphid ( Aphis glycines Matsumura) as a devastating insect pest of soybean ( Glycine max (L.) Merr.) in the United States, host resistance was recognized as an important management option. However, the identification of soybean aphid isolates exhibiting strong virulence against aphid resistance genes ( Rag genes) has highlighted the need for pyramiding genes to help ensure the durability of host resistance as a control strategy. In this study, soybean isolines with all possible combinations of the resistance and susceptibility alleles at Rag1 , RAG2 , and Rag3 were evaluated for their effectiveness against the four characterized soybean aphid biotypes. All soybean isolines, including the susceptible check carrying none of the resistance alleles (S1/S2/S3), were infested with each biotype in no-choice greenhouse tests, and the aphid populations developed on each isoline were enumerated 14 d after infestation. All gene combinations, with the exception of Rag3 alone, provided excellent protection against biotype 1. Isolines with RAG2 alone or in combination with Rag1 and Rag3 had greater levels of resistance to biotype 2 than those with either Rag1 alone, Rag3 alone, or the Rag1/3 pyramid. For biotype 3, the Rag1/3 and Rag1/2/3 pyramided lines significantly reduced aphid populations compared with all other gene combinations, while the Rag1/2/3 pyramid provided the greatest protection against biotype 4. Overall, the Rag1/2/3 pyramided line conferred the greatest protection against all four biotypes.
-
identification and molecular mapping of two soybean aphid resistance genes in soybean pi 587732
Theoretical and Applied Genetics, 2014Co-Authors: Anitha Chirumamilla, Curtis B Hill, Glen L Hartman, Brian W DiersAbstract:Soybean [Glycine max (L.) Merr.] continues to be plagued by the soybean aphid (Aphis glycines Matsumura: SA) in North America. New soybean resistance sources are needed to combat the four identified SA biotypes. The objectives of this study were to determine the inheritance of SA resistance in PI 587732 and to map resistance gene(s). For this study, 323 F2 and 214 F3 plants developed from crossing PI 587732 to two susceptible genotypes were challenged with three SA biotypes and evaluated with genetic markers. Choice tests showed that resistance to SA Biotype 1 in the first F2 population was controlled by a gene in the Rag1 region on chromosome 7, while resistance to SA Biotype 2 in the second population was controlled by a gene in the RAG2 region on chromosome 13. When 134 F3 plants segregating in both the Rag1 and RAG2 regions were tested with a 1:1 mixture of SA Biotypes 1 and 2, the RAG2 region and an interaction between the Rag1 and RAG2 regions were significantly associated with the resistance. Based on the results of the non-choice tests, the resistance gene in the Rag1 region in PI 587732 may be a different allele or gene from Rag1 from Dowling because the PI 587732 gene showed antibiosis type resistance to SA Biotype 2 while Rag1 from Dowling did not. The two SA resistance loci and genetic marker information from this study will be useful in increasing diversity of SA resistance sources and marker-assisted selection for soybean breeding programs.
