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Browsing by Subject "Puccinia graminis"

Now showing 1 - 5 of 5
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    Barley stem rust resistance genes: structure and function
    (Plant Genome, 2009-07) Steffenson, Brian; Kleinhofs, Andris; Brueggeman, Robert; Nirmala, Jayaveeramuthu; Zhang, Ling; Mirlohi, Aghafakhr; Druka, Arnis; Rostoks, Nils
    Rusts are biotrophic pathogens that attack many plant species but are particularly destructive on cereal crops. The stem rusts (caused by Puccinia graminis) have historically caused severe crop losses and continue to threaten production today. Barley (Hordeum vulgare L.) breeders have controlled major stem rust epidemics since the 1940s with a single durable resistance gene Rpg1. As new epidemics have threatened, additional resistance genes were identified to counter new rust races, such as the rpg4/Rpg5 complex locus against races QCCJ and TTKSK. To understand how these genes work, we initiated research to clone and characterize them. The Rpg1 gene encodes a unique protein kinase with dual kinase domains, an active kinase, and a pseudokinase. Function of both domains is essential to confer resistance. The rpg4 and Rpg5 genes are closely linked and function coordinately to confer resistance to several wheat (Triticum aestivum L.) stem rust races, including the race TTKSK (also called Ug99) that threatens the world's barley and wheat crops. The Rpg5 gene encodes typical resistance gene domains NBS, LRR, and protein kinase but is unique in that all three domains reside in a single gene, a previously unknown structure among plant disease resistance genes. The rpg4 gene encodes an actin depolymerizing factor that functions in cytoskeleton rearrangement.
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    Identification of new resistance loci to African stem rust race TTKSK in tetraploid wheats based on linkage and genome-wide association mapping
    (Frontiers in Plant Science, 2015-12-09) Laido, Giovanni; Panio, Giosue; Marone, Daniela; Russo, Maria A; Ficco, Donatella B. M.; Giovaniello, Valentina; Cattivelli, Luigi; Steffenson, Brian; De Vita, Pasquale; Mastrangelo, Anna M
    Stem rust, caused by Puccinia graminis Pers. f. sp. tritici Eriks. and E. Henn. (Pgt), is one of the most destructive diseases of wheat. Races of the pathogen in the “Ug99 lineage” are of international concern due to their virulence for widely used stem rust resistance genes and their spread throughout Africa. Disease resistant cultivars provide one of the best means for controlling stem rust. To identify quantitative trait loci (QTL) conferring resistance to African stem rust race TTKSK at the seedling stage, we evaluated an association mapping (AM) panel consisting of 230 tetraploid wheat accessions under greenhouse conditions. A high level of phenotypic variation was observed in response to race TTKSK in the AM panel, allowing for genome-wide association mapping of resistance QTL in wild, landrace, and cultivated tetraploid wheats. Thirty-five resistance QTL were identified on all chromosomes, and seventeen are of particular interest as identified by multiple associations. Many of the identified resistance loci were coincident with previously identified rust resistance genes; however, nine on chromosomes 1AL, 2AL, 4AL, 5BL, and 7BS may be novel. To validate AM results, a biparental population of 146 recombinant inbred lines was also considered, which derived from a cross between the resistant cultivar “Cirillo” and susceptible “Neodur.” The stem rust resistance of Cirillo was conferred by a single gene on the distal region of chromosome arm 6AL in an interval map coincident with the resistance gene Sr13, and confirmed one of the resistance loci identified by AM. A search for candidate resistance genes was carried out in the regions where QTL were identified, and many of them corresponded to NBS-LRR genes and protein kinases with LRR domains. The results obtained in the present study are of great interest as a high level of genetic variability for resistance to race TTKSK was described in a germplasm panel comprising most of the tetraploid wheat sub-species.
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    Proteolysis of the barley receptor-like protein kinase RPG1 by a proteasome pathway is correlated with Rpg1-mediated stem rust resistance
    (Proceedings of the National Academy of Sciences of the United States of America, 2007-06-12) Steffenson, Brian; Nirmala, Jayaveeramuthu; Dahl, Stephanie; Kannangara, C.Gamini; Wettstein, Diter von; Chen, Xianming; Kleinhofs, Andris
    In plants, disease resistance mediated by the gene-for-gene mechanism involves the recognition of specific effector molecules produced by the pathogen either directly or indirectly by the resistance-gene products. This recognition triggers a series of signals, thereby serving as a molecular switch in regulating defense mechanisms by the plants. To understand the mechanism of action of the barley stem rust resistance gene Rpg1, we investigated the fate of the RPG1 protein in response to infection with the stem rust fungus, Puccinia graminis f. sp. tritici. The investigations revealed that RPG1 disappears to undetectable limits only in the infected tissues in response to avirulent, but not virulent pathotypes. The RPG1 protein disappearance is rapid and appears to be due to specific protein degradation via the proteasome-mediated pathway as indicated by inhibition with the proteasomal inhibitor MG132, but not by other protease inhibitors.
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    The stem rust resistance gene Rpg5 encodes a protein with nucleotide-binding-site, leucine-rich, and protein kinase domains
    (Proceedings of the National Academy of Sciences of the United States of America, 2008-08-01) Steffenson, Brian; Brueggeman, R.; Druka, A.; Nirmala, J.; Cavileer, T.; Drader, T.; Rostoks, N.; Mirlohi, A.; Bennypaul, H.; Gill, U.; Kudrna, D.; Whitelaw, C.; Kilian, A.; Han, F.; Sun, Y.; Gill, K.; Kleinhofs, A.
    We isolated the barley stem rust resistance genes Rpg5 and rpg4 by map-based cloning. These genes are colocalized on a 70-kb genomic region that was delimited by recombination. The Rpg5 gene consists of an unusual structure encoding three typical plant disease resistance protein domains: nucleotide-binding site, leucine-rich repeat, and serine threonine protein kinase. The predicted RPG5 protein has two putative transmembrane sites possibly involved in membrane binding. The gene is expressed at low but detectable levels. Posttranscriptional gene silencing using VIGS resulted in a compatible reaction with a normally incompatible stem rust pathogen. Allele sequencing also validated the candidate Rpg5 gene. Allele and recombinant sequencing suggested that the probable rpg4 gene encoded an actin depolymerizing factor-like protein. Involvement of actin depolymerizing factor genes in nonhost resistance has been documented, but discovery of their role in gene-for-gene interaction would be novel and needs to be further substantiated.
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    Studies On Wheat Resistance To UG99
    (2010-10) Rouse, Matthew
    Wheat stem rust caused by the fungus Puccinia graminis f. sp. tritici (Pgt) has historically been a devastating disease of wheat. In 1998, a race of Pgt was detected in Uganda that is virulent to the majority of wheat cultivars being grown. This new race, commonly referred to as Ug99, was characterized as race TTKSK based upon the North American stem rust differentials. Race TTKSK has recently spread throughout eastern and southern Africa, and into the Middle East. Data suggest that Ug99 can alternatively be described as Pgt race PTKSK, based upon demonstrated avirulence to stem rust resistance gene Sr21. Accessions of wild relatives of wheat, Triticum monococcum, T. urartu, and Aegilops tauschii were screened with Pgt race TTKSK. Crosses among resistant and susceptible accessions of T. monococcum led to the characterization of two new stem rust resistance genes effective to Pgt-TTKSK. Preliminary screening of 700 accessions of spring wheat led to the identification of 88 accessions with resistance to Ug99. Examination of the genetics of resistance in one of these accessions, SD 1691, identified Sr28 as conferring a high level of resistance. Molecular markers linked to Sr28 were identified on chromosome arm 2BL. Examination of the genetics of resistance in Gabo 56 indicated the presence of a single dominant gene. This gene was temporarily designated as SrGabo56 and mapped on chromosome arm 2BL. Segregation of resistance in the progeny of the cross between SD 1691 and Gabo 56 indicated that Sr28 and SrGabo56 are linked. Characterization of the genetics of resistance to Pgt-TTKSK in synthetic wheat TA4152-37, resulted in the identification of Sr13 in TA4152-37. Molecular markers linked to Sr13 in hexaploid wheat were identified on chromosome arm 6AL. Overall, 3 new stem rust resistance genes effective to Pgt-TTKSK were identified. Molecular markers linked to SrGabo56, Sr13, and Sr28 were described. The identification of markers linked to multiple stem rust resistance genes will facilitate the combination of these genes in breeding lines. The identification of the new sources of resistance to Pgt-TTKSK will provide plant breeders with additional tools to protect wheat from this dangerous race.