Identification of Wheat Leaf Rust (Puccinia Triticina. ERIKS.) Genes Expressed During the Early Stages of Infection PDF Download
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Author: Vanesa Segovia Publisher: ISBN: Category : Languages : en Pages :
Book Description
In Kansas, wheat (Triticum aestivum L.) is severely affected by the biotrophic fungus Puccinia triticina (leaf rust). Although resistant varieties have been developed, the fungus tends to overcome new sources resistance very quickly. Plants have evolved a single gene (R genes) defense network that can recognize specific pathogen effectors (Avr), in a gene-for-gene manor. In rusts, effectors are secreted proteins responsible for inducing the uptake of nutrients and inhibit host defense responses. Identification of secreted proteins during the infection may help to understand the mode of infection of P. triticina. Little is known about molecular interactions in the pathosystem wheat-leaf rust and no Avr genes from cereal rusts have been cloned. In order to understand pathogenicity in leaf rust and generate new alternatives for disease control, the goal of this research is identify P. triticina secreted proteins from a collection of expressed genes during the infection, and to characterize putative Avr function for three candidates. From 432 EST's derived from haustoria and infected plants, fifteen secreted proteins were identified and 10 were selected as potential avirulence candidates. Pt3 and Pt 51 are two P. triticina (Pt) candidates expressed specifically in the haustoria and encode small cysteine-rich secreted proteins. Eight candidates are expressed at early stages of infection, during spore germination and 6 days after inoculation. They are small-secreted proteins. None are repetitive elements or have nuclear localization signals. They also do not share a conserved motif with known filamentous fungus Avr proteins. Five candidates are novel proteins, two have similarity with predicted proteins, one is homologous with Hesp-379-like protein, one is homologous with superoxide dismutase, and one has a cell glucanase predicted function. Pt3, Pt12 and Pt27 were tested by transient expression experiments using co-bombardment with GUS into leaf rust resistant isogenic lines. Reduction in the expression of reporter gene GUS co-expressed with Pt27 indicates a potential avirulence factor for Lr26 in wheat.
Author: Vanesa Segovia Publisher: ISBN: Category : Languages : en Pages :
Book Description
In Kansas, wheat (Triticum aestivum L.) is severely affected by the biotrophic fungus Puccinia triticina (leaf rust). Although resistant varieties have been developed, the fungus tends to overcome new sources resistance very quickly. Plants have evolved a single gene (R genes) defense network that can recognize specific pathogen effectors (Avr), in a gene-for-gene manor. In rusts, effectors are secreted proteins responsible for inducing the uptake of nutrients and inhibit host defense responses. Identification of secreted proteins during the infection may help to understand the mode of infection of P. triticina. Little is known about molecular interactions in the pathosystem wheat-leaf rust and no Avr genes from cereal rusts have been cloned. In order to understand pathogenicity in leaf rust and generate new alternatives for disease control, the goal of this research is identify P. triticina secreted proteins from a collection of expressed genes during the infection, and to characterize putative Avr function for three candidates. From 432 EST's derived from haustoria and infected plants, fifteen secreted proteins were identified and 10 were selected as potential avirulence candidates. Pt3 and Pt 51 are two P. triticina (Pt) candidates expressed specifically in the haustoria and encode small cysteine-rich secreted proteins. Eight candidates are expressed at early stages of infection, during spore germination and 6 days after inoculation. They are small-secreted proteins. None are repetitive elements or have nuclear localization signals. They also do not share a conserved motif with known filamentous fungus Avr proteins. Five candidates are novel proteins, two have similarity with predicted proteins, one is homologous with Hesp-379-like protein, one is homologous with superoxide dismutase, and one has a cell glucanase predicted function. Pt3, Pt12 and Pt27 were tested by transient expression experiments using co-bombardment with GUS into leaf rust resistant isogenic lines. Reduction in the expression of reporter gene GUS co-expressed with Pt27 indicates a potential avirulence factor for Lr26 in wheat.
Author: Kerri Allison Neugebauer Publisher: ISBN: Category : Languages : en Pages :
Book Description
Bread wheat (Triticum aestivum L.) is an important staple crop for 35% of the world population. One economically important pathogen of wheat is Puccinia triticina, the causal agent of leaf rust, can cause up to 50% yield loss during epidemics. Despite the lack of an alternate host to complete the sexual stages, P. triticina still has variation within the population, which can make achieving durable resistance difficult. This study aims to gain a better understanding of the P. triticina-wheat interaction by identifying wheat genes that are induced by individual and multiple races. Six P. triticina races were evaluated on a susceptible variety of wheat at six days post inoculation. RNA was sequenced and 63 wheat genes were identified that showed varying expression in response to the six P. triticina races. Fifty-four wheat genes were characterized during the first seven days of infection using real-time PCR. Race specific gene expression was found in three wheat genes with race differences on Lr2A, Lr2C, and Lr17A. Wheat genes that had similar expression in response to all six races were also identified. Seven of the characterized genes were then silenced using RNAi hairpin constructs. The transgenic plants were molecularly characterized and inoculated with a virulent P. triticina race in the T2 generation. However, the endogenous genes were not silenced and the transgenic plants maintained susceptibility. A mutation approach was also used to identify wheat genes involved in infection. A mutant population of 3780 wheat plants was created using EMS. Fifteen hundred mutants from the M1 population were screened for plants with a different infection phenotype compared to the non-mutated control and 570 were selected. After two additional generations of selection, eight resistant mutants were obtained. The gene expression of the seven previously identified genes were evaluated and one mutant showed reduced expression of an ER molecular chaperone gene. This research uses a forward and reverse genetics approach to identify and evaluate the function of wheat genes in the wheat-P. triticina interaction. Although RNAi could not determine the gene function, the knockout mutant shows that the identified genes may have a crucial role in infection.
Author: Joseph Fenoglio Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Leaf Rust, caused by Puccinia triticina, is a major disease of wheat. Leaf rust has proven to be a resilient pathogen, overcoming resistance genes multiple times. Plants have factors, known as susceptibility genes, that facilitate the ability of pathogens to cause disease. Altering susceptibility genes may provide a more durable defense against infection than resistance genes but have yet to be identified for susceptibility to leaf rust in wheat. By characterizing random mutants created through chemical mutagenesis, mechanisms determining wheat susceptibility to leaf rust can be determined. The susceptible wheat variety Thatcher was mutagenized using ethyl methanesulfonate (EMS). Surviving plants were scored for a reduction in pustule size or quantity when challenged with leaf rust. From these plants, three mutant lines (1995, 2048, and 2348) have been obtained. Mutant lines 1995 and 2048 exhibit a constitutive hypersensitive-like response (HR-like). Mutant line 2348 exhibits no evidence of a HR. Microscopic analysis of the initial 5 days of the infection process revealed the ability of P. triticina to form appressoria, early colonization, and pustule development was altered in 1995 and 2048. In 2348, P. triticina was less able to progress beyond appressoria formation and intercellular hyphae than in Thatcher. Bulked segregant RNAseq analysis of F[subscript 2:3] pools of tissue originating from a backcross to the wild type parent revealed an induction of the plant defense response in 1995 and 2048. Genotypic studies were conducted to identify regions that may contain the causative mutation. A F4 mapping population was generated by crossing each mutant line with the hard red winter wheat variety KS061705M11 and utilizing single seed descent. Association mapping identified SNPs within each population that associated with the mutant phenotype. Confidence intervals surrounding each identified SNP were created through haplotype blocking. A second genotyping method, exome capture, identified SNPs in M8 lines for each mutant. Using the confidence intervals from association mapping, the list of SNPs from exome capture was narrowed. Mutant line 1995 mapped to a 3.89Mb window on 2D, a 7Mb window on 3A, and a 4.85Mb window on 4B. Mutant line 2048 mapped to a 3.89Mb window on 3B and a 4.52Mb window on 4B. These intervals narrow the region of interest for future fine mapping studies that seek to identify the causative mutation.
Author: RA McIntosh Publisher: CSIRO PUBLISHING ISBN: 0643103023 Category : Technology & Engineering Languages : en Pages : 308
Book Description
Although stem rust has been controlled by means of resistant cultivars, leaf and stripe rust continue as problems for many growing areas of the world. Wheat Rusts: An Atlas of Resistance Genes has been prepared by specialists from one of the leading international laboratories, and illustrates with colour photographs typical resistance phenotypes associated with most known genes for resistance to the three rust diseases of wheat. Relevant details for each gene include chromosome location, aspects of genetics and pathogen variation, the effects of environment on expression, origin, availability in genetic and breeding stocks, and use in agriculture. This atlas includes an introduction to host:pathogen genetics, methodologies for wheat rust research and breeding for resistance.
Book Description
The fungus Puccinia graminis f. sp. tritici (Pgt) is the causal agent of the wheat stem rust disease. Wheat stem rust has attracted a lot of attention after the emergence of the Ug99 race group, which at the time of its origin was virulent on most of the wheat varieties cultivated around the world. The evolution and spread of the Pgt isolates from the Ug99 race group posed a serious threat to worldwide wheat production. To mitigate the potential impact of new rust epidemics in major wheat production areas, it remains critical to identify new strategies for breeding durable resistance traits. A detailed understanding of the plant-pathogen interaction mechanisms in the wheat-Pgt pathosystem should be the foundation of these strategies. The interaction between the matching pair of resistance (R) and avirulence (Avr) genes, an important element of the plant-pathogen interactions, is described by the broadly documented gene-for-gene model. The cloning of the Sr35 gene, which confers near immunity against all isolates from the Ug99 race group provided a unique opportunity to investigate the molecular mechanisms of resistance to stem rust in wheat. The goals of the present study were: (1) to determine whether the Sr35 gene alone is sufficient for conferring resistance against Ug99, (2) to assess the Sr35 transcript levels during the time course of infection, and (3) to identify and validate the corresponding Avr gene interacting with Sr35. The cloning of Avr genes from the biotrophic fungi represents a substantial challenge due to the variability, redundant nature, the lack of similarity to known proteins, and lack of adequate functional tools to validate them. To overcome these limitations, we performed a comparative genomic analysis using multiple Sr35-avirulent and Sr35-virulent races, including 15 chemically mutagenized Pgt strains that acquired virulence on the Sr35 gene. Whole genome shotgun sequencing of the Pgt mutants identified a single candidate gene, which carried strong effect mutations in each mutant strain. The Avr gene candidate (AvrSr35) was expressed at early stages of infection and had a signal peptide indicating that the gene product is secreted. Comparative microscopic analysis of the infected tissues at different time points after infection indicated that AvrSr35 secretion occurs before haustoria formation. The re-sequencing of the AvrSr35 candidate gene in a panel of Sr35-virulent and Sr35-avirulent isolates including isolates from the Ug99 race group, revealed the presence of a mobile DNA element inserted into the coding sequence of virulent isolates. This insertion resulted in a premature termination codon and explains the origin of Pgt field isolates virulent in the presence of the Sr35 gene. Co-expression of AvrSr35 with the Sr35 in N. benthamiana leaves induced a specific hypersensitive response confirming the avirulence function of the candidate effector gene. Subcellular localization, bi-molecular fluorescence complementation, and co-immunoprecipitation assays in N. benthamiana leaves revealed that the AvrSr35 and Sr35 proteins interact and are likely associated with the endoplasmic reticulum and plasma membrane. Thus, this study identified and functionally characterized the first matching pair of Avr/R genes for cereal rusts.
Author: Tesfay Gebrekirstos Gebremariam Publisher: LAP Lambert Academic Publishing ISBN: 9783659664250 Category : Languages : en Pages : 84
Book Description
Leaf rust (Puccinia triticina Eriks and Henn.) is one of the most important diseases of wheat in Tigray region. Regular surveying, race analysis and searching resistant genes plays significant role to develop resistant varieties against leaf rust. Hence, this study was carried out to determine the distribution and intensity leaf rust, identify physiologic races and evaluate the reaction of commonly growing wheat varieties to virulent races of leaf rust. During the survey,108 farmers' wheat fields and experimental plots were assessed in five districts of Southeastern Tigray, of which 95 (88%) of the fields were affected with leaf rust. The overall mean incidence and severity of the disease were 48.4 and 18.2%, respectively. According to the North American system of nomenclature for P.triticina, characterization of 40 mono pustules resulted in the identification of 22 races. The broadest virulence spectrum was recorded from TKTT race, making all Lr genes except Lr9 ineffective. The variety evaluation revealed that, Mekelle-3, Mekelle-4, Picaflor, Dashin and local showed susceptible reaction to TKTT, THTT and PHTT races
Author: Xianming Chen Publisher: Springer ISBN: 9402411119 Category : Science Languages : en Pages : 723
Book Description
This book comprehensively introduces stripe rust disease, its development and its integral control. Covering the biology, genetics, genome, and functional genomics of the pathogen, it also discusses host and non-host resistance, their interactions and the epidemiology of the disease. It is intended for scientists, postgraduates and undergraduate studying stripe rust, plant pathology, crop breeding, crop protection and agricultural science, but is also a valuable reference book for consultants and administrators in agricultural businesses and education.
Author: Marley Boyce Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Wheat leaf rust, caused by Puccinia triticina Eriks. (= P. recondita Rob. Ex Desmaz. f. sp. tritici), is the most widespread disease of wheat worldwide and causes average annual yield losses of 5 to 25%. The emergence of a new predominant race of leaf rust, TDBG, in the 2004 Canadian virulence survey led to the identification of a second leaf rust resistance gene segregating in the Thatcher-Lr1 near-isogenic differential line, RL6003, which produced an unusual mesothetic infection type. This gene was subsequently isolated in a Thatcher background and temporarily designated as LrCen (Tc-LrCen). A cross was made with a susceptible parent (Tc-LrCen/ Sumai3-lr34) and a doubled haploid (DH) mapping population was generated from the hybrids. Parental lines and 180 double haploid (DH) individuals were phenotyped with race TDBG and a 1:1 ratio was observed in the DH population. Parental lines and 94 DH individuals were genotyped with the Illumina Infinium assay using a custom iSelect 90K wheat SNP array. Two-point linkage between the phenotype and polymorphic SNP markers identified linked markers. A BLAST search of linked SNP sequences was performed against the Wheat Survey Sequence providing a putative chromosomal location of 7AL. Subsequent mapping with microsatellite markers confirmed LrCen was located on the long arm of chromosome 7A flanked by gwm344 (9.5 cM) and cfa2240 (0.6 cM) as well as a group of co-segregating SNPs also at a genetic distance of 0.6 cM. When the SNP sequences were converted to the kompetitive allele specific PCR (KASP) markers they were found to be dominant, making them less useful for marker assisted selection in populations with heterozygotes. LrCen mapped distal to Lr20; the only other Lr gene previously identified on chromosome 7AL.
Author: Vanesa Segovia
Author: Vanesa Segovia
Author: Kerri Allison Neugebauer
Author: Rico A. Caldo
Author: Joseph Fenoglio
Author: RA McIntosh
Author: Alan P. Roelfs
Author: Andrés Felipe Salcedo
Author: Tesfay Gebrekirstos Gebremariam
Author: Xianming Chen
Author: Marley Boyce