Nucleoli in differentiated germ tubes of wheat rust uredospores

1970 ◽  
Vol 48 (9) ◽  
pp. 1693-1695 ◽  
Author(s):  
Larry D. Dunkle ◽  
William P. Wergin ◽  
Paul J. Allen
Keyword(s):  
Electron Microscopy ◽  
Heat Shock ◽  
Nuclear Envelope ◽  
Outer Membrane ◽  
Ribosomal Rna ◽  
Stem Rust ◽  
Wheat Stem Rust ◽  
Cytoplasmic Structures ◽  
Germ Tubes ◽  
Wheat Rust

Nucleoli observed by electron microscopy are illustrated in germ tubes of wheat stem rust uredospores which have been induced by heat shock to differentiate infection structures. The presence of nucleoli in these structures suggests that this obligate parasite may possess the capacity of synthesizing ribosomal RNA independently of its host. In addition to nucleoli, heterochromatin is characteristically observed appressed to the inner membrane of the nuclear envelope. This material is associated with distinct cytoplasmic structures which are appressed to the outer membrane of the nuclear envelope and resemble developing centrioles in other fungi.

Ribonucleic acids of differentiating and non-differentiating uredosporelings of wheat stem rust

1974 ◽  
Vol 52 (6) ◽  
pp. 1309-1317 ◽  
Author(s):  
W. K. Kim ◽  
R. Rohringer
Keyword(s):  
Ribosomal Rna ◽  
Stem Rust ◽  
Gel Electrophoresis ◽  
Gradient Centrifugation ◽  
Sucrose Density Gradient ◽  
Wheat Stem Rust ◽  
Sucrose Density Gradient Centrifugation ◽  
Ribonucleic Acids ◽  
Molecular Weights ◽  
Germ Tubes

Uredospores of wheat stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn.) were deposited onto Millipore membranes and allowed to germinate. Those remaining continuously at 20° formed germ tubes only (non-differentiated), but those exposed to 30° for 90 min after the first 2 h of germination developed infection structures corresponding to appressoria and substomatal vesicles (differentiated).Nucleic acids were extracted with a phenol method from resting uredospores and from differentiated and non-differentiated sporelings. The amount of extractable RNA decreased as germination progressed, but no RNA was detected in the germination medium. The decrease in extractable RNA (up to 40%) occurred in both differentiated and non-differentiated sporelings.Acrylamide gel electrophoresis was used to separate RNA species and to determine their approximate molecular weights (in daltons): sporelings contained 25-S (1.65 × 106) and 18-S (0.80 × 106) ribosomal RNA (rRNA), 5-S (3.6 × 104) rRNA, and 4.5-S (2.4 × 104) transfer RNA (tRNA). Radioactive uridine, fed to sporelings, was incorporated mostly into 5-S rRNA and (or) tRNA.Acrylamide gel electrophoresis and sucrose density gradient centrifugation revealed that differentiated sporelings contained a type of RNA that was not detected in non-differentiated sporelings. It was heterogeneous and migrated in the 16-S to 5-S interval on polyacrylamide gels. Some of the RNA present in this fraction may have been preformed in resting spores and released from more complex material during the process of differentiation.

scholarly journals The nucleolus of wheat stem rust uredospores

1969 ◽  
Vol 47 (12) ◽  
pp. 1887-1889 ◽  
Author(s):  
Stephen Mitchell ◽  
Michael Shaw
Keyword(s):  
Electron Microscopy ◽  
Ribosomal Rna ◽  
Stem Rust ◽  
Ribonucleic Acid ◽  
Acid Formation ◽  
Puccinia Graminis ◽  
Wheat Stem Rust ◽  
Puccinia Graminis Tritici ◽  
Mean Diameter

Electron microscopy shows that the nuclei in immature uredospores of Puccinia graminis tritici possess prominent nucleoli with a mean diameter of 1.7 ± 0.4 μ. The nucleoli in mature uredospores are much smaller (0.5 μ). This reduction in size of the nucleoli may indicate that ribosomal RNA (ribonucleic acid) formation is repressed as uredospores mature.

FINE STRUCTURE OF WHEAT STEM RUST UREDOSPORES

1964 ◽  
Vol 42 (11) ◽  
pp. 1503-1508 ◽  
Author(s):  
P. G. Williams ◽  
G. A. Ledingham
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Higher Plants ◽  
Puccinia Graminis ◽  
Resting Cells ◽  
Oil Bodies ◽  
Wheat Stem Rust ◽  
Cytoplasmic Structures ◽  
Vacuolar Membranes ◽  
Germ Tubes

The fine structure of uredospores and germ tubes of Puccinia graminis f. sp. trilici is described from electron micrographs of cells fixed in KMnO4. In terms of their principal cytoplasmic structures (nuclei, mitochondria, endoplasmic reticulum, and protoplasmic and vacuolar membranes) these cells bear a general resemblance to other fungi and higher plants but differences between resting cells and germ tubes were noted in the size of oil bodies and the structure and extent of the endoplasmic reticulum.

Electron microscopy of susceptible and resistant near-isogenic (sr6/Sr6) lines of wheat infected by Puccinia graminis tritici. III. Ultrastructure of incompatible interact

1979 ◽  
Vol 57 (23) ◽  
pp. 2626-2634 ◽  
Author(s):  
D. E. Harder ◽  
D. J. Samborski ◽  
R. Rohringer ◽  
S. R. Rimmer ◽  
W. K. Kim ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Stem Rust ◽  
Stem Rust Resistance ◽  
Temperature Sensitive ◽  
Puccinia Graminis ◽  
Cell Necrosis ◽  
Mitochondrial Membranes ◽  
Wheat Stem Rust ◽  
Mesophyll Cells ◽  
Mother Cells

The interaction between avirulent wheat stem rust and wheat mesophyll cells containing the temperature-sensitive Sr6 gene for stem rust resistance was studied by electron microscopy. Mesophyll cells that were invaded at 26 °C (conditioning compatibility) did not develop any signs of incompatibility after they were transferred to 19 °C, at which temperature incompatibility is normally expressed. In host tissue that appeared to be invaded after the change from 26 to 19 °C, the early ultrastructural symptoms of incompatibility were a more electron-dense and often perforated invaginated host plasmalemma, disruptions of the noninvaginated host plasmalemma, vacuolation of the cytoplasm, and accumulations of electron-dense material along the membranes of the vacuoles. At later stages in the development of incompatible interactions, the electron-dense accumulations along the vacuole membranes increased in size and occurred along chloroplast and mitochondrial membranes. Eventually, the entire protoplasts were electron dense and collapsed. In haustoria and haustorial mother cells, incompatibility was usually expressed by a uniform increase in electron density of the cytoplasm. In the Sr6/P6 interaction at 19 °C, host cell necrosis was not always accompanied by fungal necrosis or vice versa. In Sr5/P5 interactions, which were examined for comparison, the intracellular symptoms of incompatibility were similar to those of the Sr6/P6 interactions.

scholarly journals Synthesis of differentiation-specific proteins in germlings of the wheat stem rust fungus after heat shock

1985 ◽  
Vol 9 (3) ◽  
pp. 9-83 ◽  
Author(s):  
R. Wanner ◽  
H. Fo¨rster ◽  
K. Mendgen ◽  
R.C. Staples
Keyword(s):  
Heat Shock ◽  
Stem Rust ◽  
Rust Fungus ◽  
Wheat Stem Rust ◽  
Specific Proteins

scholarly journals Visualization of inositol 1,4,5-trisphosphate receptors on the nuclear envelope outer membrane by freeze-drying and rotary shadowing for electron microscopy

2010 ◽  
Vol 171 (3) ◽  
pp. 372-381 ◽  
Author(s):  
Cesar Cárdenas ◽  
Matias Escobar ◽  
Alejandra García ◽  
Maria Osorio-Reich ◽  
Steffen Härtel ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Outer Membrane ◽  
Freeze Drying ◽  
Inositol 1,4,5 Trisphosphate ◽  
Rotary Shadowing

scholarly journals Wheat rust epidemics damage Ethiopian wheat production: A decade of field disease surveillance reveals national-scale trends in past outbreaks

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0245697
Author(s):  
M. Meyer ◽  
N. Bacha ◽  
T. Tesfaye ◽  
Y. Alemayehu ◽  
E. Abera ◽  
...  
Keyword(s):  
Leaf Rust ◽  
Stem Rust ◽  
Disease Prevalence ◽  
Spatial Data Analysis ◽  
Disease Spread ◽  
Economic Losses ◽  
Wheat Stem Rust ◽  
Wheat Production ◽  
Wheat Rust ◽  
Wheat Rusts

Wheat rusts are the key biological constraint to wheat production in Ethiopia—one of Africa’s largest wheat producing countries. The fungal diseases cause economic losses and threaten livelihoods of smallholder farmers. While it is known that wheat rust epidemics have occurred in Ethiopia, to date no systematic long-term analysis of past outbreaks has been available. We present results from one of the most comprehensive surveillance campaigns of wheat rusts in Africa. More than 13,000 fields have been surveyed during the last 13 years. Using a combination of spatial data-analysis and visualization, statistical tools, and empirical modelling, we identify trends in the distribution of wheat stem rust (Sr), stripe rust (Yr) and leaf rust (Lr). Results show very high infection levels (mean incidence for Yr: 44%; Sr: 34%; Lr: 18%). These recurrent rust outbreaks lead to substantial economic losses, which we estimate to be of the order of 10s of millions of US-D annually. On the widely adopted wheat variety, Digalu, there is a marked increase in disease prevalence following the incursion of new rust races into Ethiopia, which indicates a pronounced boom-and-bust cycle of major gene resistance. Using spatial analyses, we identify hotspots of disease risk for all three rusts, show a linear correlation between altitude and disease prevalence, and find a pronounced north-south trend in stem rust prevalence. Temporal analyses show a sigmoidal increase in disease levels during the wheat season and strong inter-annual variations. While a simple logistic curve performs satisfactorily in predicting stem rust in some years, it cannot account for the complex outbreak patterns in other years and fails to predict the occurrence of stripe and leaf rust. The empirical insights into wheat rust epidemiology in Ethiopia presented here provide a basis for improving future surveillance and to inform the development of mechanistic models to predict disease spread.

scholarly journals Sr31-Virulent Races (TTKSK, TTKST, and TTTSK) of the Wheat Stem Rust Pathogen Puccinia graminis f. sp. tritici are Present in Tanzania

Plant Disease ◽  
2013 ◽  
Vol 97 (4) ◽  
pp. 557-557 ◽  
Author(s):  
I. L. Hale ◽  
I. Mamuya ◽  
D. Singh
Keyword(s):  
Stem Rust ◽  
Hot Spots ◽  
Disease Assessment ◽  
Puccinia Graminis ◽  
Wheat Stem Rust ◽  
Smallholder Farms ◽  
Northern Tanzania ◽  
Arusha Region ◽  
First Time ◽  
Wheat Rust

Since the first detection of race TTKSK (syn. Ug99) in Uganda in 1999 (2), the migration and evolution of Sr31-virulent races of Puccinia graminis f. sp. tritici [Pgt] have been closely monitored, particularly in Kenya and countries north, along the likely trajectory of migration to major wheat-producing regions of Asia. More recently, surveillance efforts have been undertaken to the south as well, and Ug99-related races have been detected in South Africa and Zimbabwe (3,4). Here we report for the first time results of a survey conducted in Tanzania. Systematic race surveillance provides data not only on the current distribution of the Ug99 race group, but also on the possible points of origin as well as the pace and probable paths of dispersal of future races from the region. In this context, the presence or absence of the Ug99 group of wheat stem rust races in adjacent countries like Tanzania assumes regional, and possibly global, relevance. A preliminary survey conducted in September 2006 indicated the presence of Sr31-virulent races of Pgt outside Slahhamo Village (3°15′S, 35°48′E) in the Ngorongoro highlands of northern Tanzania, based on compatible reactions with cv. K-Mamba (a.k.a. Mwamba), a cultivar whose pedigree indicates the presence of Sr31. A broader survey was conducted in August 2009, during which infected tissue was collected from currently-grown cultivars in research plots and on large estates, as well as from the mixes of older cultivars common on smallholder farms. In all, Pgt-infected samples were collected from one site in the Arusha region [Monduli (3°16′ S, 36°24′E)], three sites in the Ngorongoro highlands [Karatu (3°20′ S, 35°40′ E), Upper Kitete (3°14′ S, 35°53′ E), and Slahhamo], one site in the Manyara region [Hanang (4°43′ S, 35°40′ E)], and one site in the Mbeya region [southern highlands (8°87′ S, 33°40′ E)], thereby giving representation to all four major wheat growing areas in the country. Sample storage, inoculation, incubation, disease assessment, and derivation of single-pustule cultures were all performed according to the methods described by Jin et al. (1). In addition to the 20 differentials in the expanded Pgt differential set of North America, we included two supplemental tester lines: Siouxland (Sr24 + Sr31) and Sisson (Sr31 + Sr36). Each single-pustule-derived isolate was evaluated for virulence on the differential and supplemental lines at least twice. A total of 39 single-pustule isolates were derived from the six collection sites. All 39 isolates were identified as belonging to the Ug99 race group, with six identified as TTKSK (all four regions), 30 identified as TTKST (Sr31 + Sr24 virulence; Arusha region and the Ngorongoro highlands), and three identified as TTTSK (Sr31 + Sr36 virulence; Manyara region and the Ngorongoro highlands). The results of this study suggest that, to more precisely locate the “hot spots” and thereby gain a better understanding of the mechanisms of novel race emergence in East Africa, it would be prudent to include Tanzania, heretofore a blank area on the wheat rust surveillance map, in future systematic race monitoring efforts. References: (1) Y. Jin et al. Plant Dis. 92:923, 2008. (2) Z. A. Pretorius et al. Plant Dis. 84:203, 2000. (3) Z. A. Pretorius et al. Plant Dis. 94:784, 2010. (4) Z. A. Pretorius et al. Plant Dis. 96:590, 2012.

scholarly journals Identification of Wheat Gene Sr35 That Confers Resistance to Ug99 Stem Rust Race Group

Science ◽  
2013 ◽  
Vol 341 (6147) ◽  
pp. 783-786 ◽  
Author(s):  
Cyrille Saintenac ◽  
Wenjun Zhang ◽  
Andres Salcedo ◽  
Matthew N. Rouse ◽  
Harold N. Trick ◽  
...  
Keyword(s):  
Stem Rust ◽  
Coiled Coil ◽  
Puccinia Graminis ◽  
Yield Losses ◽  
Wheat Stem Rust ◽  
Polyploid Wheat ◽  
A Genome ◽  
Wheat Gene ◽  
Production Areas ◽  
Wheat Rust

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a devastating disease that can cause severe yield losses. A previously uncharacterized Pgt race, designated Ug99, has overcome most of the widely used resistance genes and is threatening major wheat production areas. Here, we demonstrate that the Sr35 gene from Triticum monococcum is a coiled-coil, nucleotide-binding, leucine-rich repeat gene that confers near immunity to Ug99 and related races. This gene is absent in the A-genome diploid donor and in polyploid wheat but is effective when transferred from T. monococcum to polyploid wheat. The cloning of Sr35 opens the door to the use of biotechnological approaches to control this devastating disease and to analyses of the molecular interactions that define the wheat-rust pathosystem.

THE DEVELOPMENT OF ECHINULATION IN UREDOSPORES OF WHEAT STEM RUST

1967 ◽  
Vol 45 (3) ◽  
pp. 287-289 ◽  
Author(s):  
P. L. Thomas ◽  
P. K. Isaac
Keyword(s):  
Electron Microscopy ◽  
Stem Rust ◽  
Wheat Stem Rust ◽  
Sequence Of Events ◽  
Pass Through ◽  
Mature Size

Electron microscopy was used to determine the sequence of events in the formation of spines on the uredospore walls of P. graminis tritici. The micrographs show that spines develop to mature size beneath the uredospore wall and then move or pass through the wall to its surface during the expansion and maturation of the spore.

Sign in / Sign up

Export Citation Format

Share Document