scholarly journals Maackiain Detoxification Contributes to the Virulence of Nectria haematococca MP VI on Chickpea

1998 ◽  
Vol 11 (4) ◽  
pp. 317-326 ◽  
Author(s):  
Jürg Enkerli ◽  
Garima Bhatt ◽  
Sarah F. Covert
Keyword(s):  
Gene Loss ◽  
Nectria Haematococca ◽  
Toxic Compound ◽  
Chemically Induced ◽  
Dispensable Chromosome ◽  
Mating Population ◽  
Multiple Copies ◽  
Weakly Virulent ◽  
High Level ◽  
Highly Virulent

Nectria haematococca mating population (MP) VI isolates that contain the MAK1 gene are able to degrade maackiain, a chickpea (Cicer arietinum) phytoalexin, to a less toxic compound. To test the contribution of MAK1 to the virulence of N. haematococca MP VI on chickpea, the MAK1 gene was disrupted in a highly virulent Mak+ isolate or added to a weakly virulent Mak- isolate via transformation. The disruption of MAK1 decreased virulence to a moderate level, while addition of multiple copies of MAK1 increased virulence to either a moderate or a high level. These data demonstrate that maackiain detoxification is a determinant, but not the only determinant, of virulence in N. haematococca MP VI isolates capable of causing disease on chickpea. MAK1 is located on a 1.6-Mb conditionally dispensable chromosome. To ascertain if there are additional genes influencing virulence toward chickpea stems on the MAK1 chromosome, the loss of this chromosome was chemically induced in an isolate containing the disrupted MAK1 gene. Loss of the MAK1 chromosome did not reduce virulence toward chickpea stems further, thus indicating that no additional genes for virulence on this part of the host plant are located on the MAK1 chromosome.

scholarly journals Duplication of a Conditionally Dispensable Chromosome Carrying Pea Pathogenicity (PEP) Gene Clusters in Nectria haematococca

2007 ◽  
Vol 20 (12) ◽  
pp. 1495-1504 ◽  
Author(s):  
Hamid S. Garmaroodi ◽  
Masatoki Taga
Keyword(s):  
Pathogenic Fungi ◽  
Gene Clusters ◽  
Chromosome Counting ◽  
Nectria Haematococca ◽  
Supernumerary Chromosomes ◽  
Dosage Effects ◽  
Dispensable Chromosome ◽  
Multiple Copies ◽  
Fusion Products

A supernumerary chromosome called a conditionally dispensable chromosome (CDC) is essential for pathogenicity of Nectria haematococca on pea. Among several CDCs discovered in N. haematococca, the PDA1 CDC that harbors the pisatin demethylation gene PDA1 is one of the best-studied CDCs and serves as a model for plant-pathogenic fungi. Although the presence of multiple copies is usual for supernumerary chromosomes in other eukaryotes, this possibility has not been examined well for any CDCs in N. haematococca. In this study, we produced strains with multiple copies of the PDA1 CDC by protoplast fusion and analyzed dosage effects of this chromosome. Using multiple methods, including cytological chromosome counting and fluorescence in situ hybridization, the fusion products between two transformants derived from the same strain that bears a single PDA1 CDC were shown to contain two PDA1 CDCs from both transformants and estimated to be haploid resulting from the deletion of an extra set or sets of A chromosomes in the fused nuclei. In phenotype assays, dosage effects of PDA1 CDC in the fusion products were evident as increased virulence and homoserine-utilizing ability compared with the parents. In a separate fusion experiment, PDA1 CDC accumulated up to four copies in a haploid genome.

scholarly journals Physical Map of a Conditionally Dispensable Chromosome in Nectria haematococca Mating Population VI and Location of Chromosome Breakpoints

Genetics ◽  
2000 ◽  
Vol 155 (3) ◽  
pp. 1083-1094 ◽  
Author(s):  
Jürg Enkerli ◽  
Heather Reed ◽  
Angela Briley ◽  
Garima Bhatt ◽  
Sarah F Covert
Keyword(s):  
Dna Sequences ◽  
Physical Map ◽  
Pathogenic Fungus ◽  
Restriction Enzymes ◽  
Nectria Haematococca ◽  
Map Construction ◽  
Dispensable Chromosome ◽  
Mating Population ◽  
Polymerase Chain ◽  
Dispersed Repeats

Abstract Certain isolates of the plant pathogenic fungus Nectria haematococca mating population (MP) VI contain a 1.6-Mb conditionally dispensable (CD) chromosome carrying the phytoalexin detoxification genes MAK1 and PDA6-1. This chromosome is structurally unstable during sexual reproduction. As a first step in our analysis of the mechanisms underlying this chromosomal instability, hybridization between overlapping cosmid clones was used to construct a map of the MAK1 PDA6-1 chromosome. The map consists of 33 probes that are linked by 199 cosmid clones. The polymerase chain reaction and Southern analysis of N. haematococca MP VI DNA digested with infrequently cutting restriction enzymes were used to close gaps and order the hybridization-derived contigs. Hybridization to a probe extended from telomeric repeats was used to anchor the ends of the map to the actual chromosome ends. The resulting map is estimated to cover 95% of the MAK1 PDA6-1 chromosome and is composed of two ordered contigs. Thirty-eight percent of the clones in the minimal map are known to contain repeated DNA sequences. Three dispersed repeats were cloned during map construction; each is present in five to seven copies on the chromosome. The cosmid clones representing the map were probed with deleted forms of the CD chromosome and the results were integrated into the map. This allowed the identification of chromosome breakpoints and deletions.

scholarly journals Nht1, a Transposable Element Cloned from a Dispensable Chromosome in Nectria haematococca

1997 ◽  
Vol 10 (6) ◽  
pp. 742-749 ◽  
Author(s):  
Jürg Enkerli ◽  
Garima Bhatt ◽  
Sarah F. Covert
Keyword(s):  
Amino Acids ◽  
Transposable Element ◽  
Copy Number ◽  
Pathogenic Fungus ◽  
Repeated Dna ◽  
Nectria Haematococca ◽  
Pathogenic Potential ◽  
Dispensable Chromosome ◽  
Mating Population ◽  
Repeated Dna Sequence

Certain isolates of the plant-pathogenic fungus Nectria haematococca mating population VI (MPVI) contain dispensable chromosomes that are unstable during sexual reproduction. Several of these chromosomes carry genes for phytoalexin detoxification and thus contribute to the pathogenic potential of this organism. A repeated DNA sequence, Nht1, was cloned from one of these dispensable chromosomes in N. haematococca MPVI. One copy of the repeated element (Nht1A) was completely sequenced. It is 2,198 bp long and it possesses incomplete inverted terminal repeats (ITRs) at each end. Nht1B, a partially sequenced copy of Nht1, has complete ITRs. Nht1A appears to contain 2 introns and encodes a protein of 550 amino acids that is highly similar to the protein encoded by the Fusarium oxysporum transposon, Fot1. Due to the presence of ITRs, its repeated nature, and its similarity to Fot1, we conclude that Nht1 is a transposable element. Within North American N. haematococca MPVI populations, Nht1 is distributed discontinuously. Its copy number in different field isolates varies from zero to approximately 100 copies per genome. The Nht1A source isolate is estimated to contain nine to 11 copies of Nht1; at least six are on the chromosome from which Nht1A was cloned.

scholarly journals On cross-correlations, averages and noise in electron microscopy

2019 ◽  
Vol 75 (1) ◽  
pp. 12-18 ◽  
Author(s):  
Michael Radermacher ◽  
Teresa Ruiz
Keyword(s):  
High Resolution ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
3D Structure ◽  
Signal To Noise ◽  
High Resolution Structure ◽  
Multiple Copies ◽  
High Level ◽  
2D Images ◽  
Resolution Structure

Biological samples are radiation-sensitive and require imaging under low-dose conditions to minimize damage. As a result, images contain a high level of noise and exhibit signal-to-noise ratios that are typically significantly smaller than 1. Averaging techniques, either implicit or explicit, are used to overcome the limitations imposed by the high level of noise. Averaging of 2D images showing the same molecule in the same orientation results in highly significant projections. A high-resolution structure can be obtained by combining the information from many single-particle images to determine a 3D structure. Similarly, averaging of multiple copies of macromolecular assembly subvolumes extracted from tomographic reconstructions can lead to a virtually noise-free high-resolution structure. Cross-correlation methods are often used in the alignment and classification steps of averaging processes for both 2D images and 3D volumes. However, the high noise level can bias alignment and certain classification results. While other approaches may be implicitly affected, sensitivity to noise is most apparent in multireference alignments, 3D reference-based projection alignments and projection-based volume alignments. Here, the influence of the image signal-to-noise ratio on the value of the cross-correlation coefficient is analyzed and a method for compensating for this effect is provided.

Differences in the biochemical compositions and elicitor activity of extracellular components produced by three races of a fungal plant pathogen, Colletotrichum lindemuthianum

1980 ◽  
Vol 26 (12) ◽  
pp. 1473-1479 ◽  
Author(s):  
Aaanne J. Anderson
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Protein Band ◽  
Colletotrichum Lindemuthianum ◽  
Neutral Sugar ◽  
Sugar Composition ◽  
Fungal Plant Pathogen ◽  
Red Kidney Bean ◽  
Weakly Virulent ◽  
Protein Components ◽  
Highly Virulent

High molecular weight products from the α, β, and γ races of Colletotrichum lin-differed in their carbohydrate and protein compositions and in their abilities to elicit symptoms of a hypersensitive response in dark red kidney bean. The neutral sugar composition of the products varied in their proportions of rhamnose, mannose, galactose, and glucose. Polyacrylamide gel electrophoresis showed the protein components to be more numerous in the β race products than in the α or γ race products. Each protein band co-stained for carbohydrate. Highest elicitor activity was observed in the products from the α race, a race avirulent on dark red kidney. The products from the weakly virulent γ race were about 10-fold less active as elicitors than those of the α race. With the β race, a race highly virulent on dark red kidney, elicitor activity was 100-fold less than that of the α race.

scholarly journals Molecular analysis of SSN6, a gene functionally related to the SNF1 protein kinase of Saccharomyces cerevisiae.

1987 ◽  
Vol 7 (10) ◽  
pp. 3637-3645 ◽  
Author(s):  
J Schultz ◽  
M Carlson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Nucleotide Sequence ◽  
Temperature Sensitive ◽  
Missense Mutations ◽  
Kinase Gene ◽  
Multiple Copies ◽  
Protein Kinase Gene ◽  
Rna Disruption ◽  
High Level

Mutations in the SSN6 gene suppress the invertase derepression defect caused by a lesion in the SNF1 protein kinase gene. We cloned the SSN6 gene of Saccharomyces cerevisiae and identified its 3.3-kilobase poly(A)-containing RNA. Disruption of the gene caused phenotypes similar to, but more severe than, those caused by missense mutations: high-level constitutivity for invertase, clumpiness, temperature-sensitive growth, alpha-specific mating defects, and failure to homozygous diploids to sporulate. In contrast, the presence of multiple copies of SSN6 interfered with derepression of invertase. An ssn6 mutation was also shown to cause glucose-insensitive expression of a GAL10-lacZ fusion and maltase. The mating defects of MAT alpha ssn6 strains were associated with production of two a-specific products, a-factor and barrier, and reduced levels of alpha-factor; no deficiency of MAT alpha 2 RNA was detected. We showed that ssn6 partially restored invertase expression in a cyr1-2 mutant, although ssn6 was clearly not epistatic to cyr1-2. We also determined the nucleotide sequence of SSN6, which is predicted to encode a 107-kilodalton protein with stretches of polyglutamine and poly(glutamine-alanine). Possible functions of the SSN6 product are discussed.

scholarly journals Induced Resistance to Blackleg (Leptosphaeria maculans) Disease of Canola (Brassica napus) Caused by a Weakly Virulent Isolate of Leptosphaeria biglobosa

Plant Disease ◽  
2006 ◽  
Vol 90 (8) ◽  
pp. 1059-1064 ◽  
Author(s):  
Y. Chen ◽  
W. G. D. Fernando
Keyword(s):  
Brassica Napus ◽  
Field Experiments ◽  
Leptosphaeria Maculans ◽  
Fungal Species ◽  
Control Treatment ◽  
Water Control ◽  
Pathogenicity Group ◽  
Weakly Virulent ◽  
Leptosphaeria Biglobosa ◽  
Highly Virulent

Blackleg of canola is a disease complex of at least two fungal species: Leptosphaeria maculans and L. biglobosa. Isolates of L. biglobosa typically are weakly virulent or avirulent and are assigned to pathogenicity group 1 (PG-1). Isolates of L. maculans are highly virulent and encompass pathogenicity groups PG-2, PG-3, and PG-4. In greenhouse tests, percent lesion/leaf area (PLLA) on cotyledons of two Brassica napus cultivars, Westar and Invigor 2153, was smaller when L. biglobosa (PG-1) was either pre- or co-inoculated at 0, 12, 24, and 48 h with virulent isolates of L. maculans in PG-2, PG-3, and PG-4. On six-leaf-stage plants of Westar, the PLLA declined significantly compared with the control when the lower leaves were treated with either PG-1 or salicylic acid, then challenged with a PG-2 isolate 24 h later. In addition, the activity of four enzymes (chitinase, β-1,3-glucanase, peroxidase, and phenylalanine ammonia lyase) was greatly enhanced at 48 and 72 h when cotyledons of Westar were inoculated first with PG-1 followed by PG-2 24 h later, compared with a water control treatment. Field experiments conducted in 2003 and 2004 showed decreased blackleg severity in plants inoculated with PG-1 alone or prior to PG-2 compared with plants inoculated with PG-2 alone or prior to PG-1.

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