The use of a benomyl-resistant mutant to demonstrate latency of Colletotrichum gloeosporioides in avocado fruit

1993 ◽  
Vol 44 (4) ◽  
pp. 763 ◽  
Author(s):  
LM Coates ◽  
JAG Irwin ◽  
IF Muirhead
Keyword(s):  
Life Cycle ◽  
Ultraviolet Light ◽  
Growth Rates ◽  
Colletotrichum Gloeosporioides ◽  
Resistant Mutant ◽  
Field Conditions ◽  
Wild Type ◽  
Type Isolate ◽  
Avocado Fruit ◽  
First Time

A benomyl-resistant mutant of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc., generated by irradiating a wild-type isolate of the fungus with ultraviolet light, was used as a marker organism to demonstrate latency under field conditions. This mutant could be easily distinguished from wild-type isolates of C. gloeosporioides on the basis of growth rates on benomyl-amended media, and was as virulent in avocado fruit as wild-type isolates. Through the use of this mutant in field inoculations of avocado fruit, it was possible to demonstrate conclusively the existence, for the first time, of latency in the life cycle of C. gloeosporioides in this host. It was also shown that the fungus was able to remain latent for periods of at least 6 months.

scholarly journals Development of Colletotrichum gloeosporioides Restriction Enzyme-Mediated Integration Mutants as Biocontrol Agents Against Anthracnose Disease in Avocado Fruits

2001 ◽  
Vol 91 (2) ◽  
pp. 143-148 ◽  
Author(s):  
N. Yakoby ◽  
R. Zhou ◽  
I. Kobiler ◽  
A. Dinoor ◽  
D. Prusky
Keyword(s):  
Restriction Enzyme ◽  
Insertional Mutagenesis ◽  
Colletotrichum Gloeosporioides ◽  
Fungal Genome ◽  
Symptom Development ◽  
Wild Type ◽  
Fresh Weight ◽  
Type Isolate ◽  
Avocado Fruit ◽  
Virulence Assay

Reduced-pathogenicity mutants of the avocado fruit pathogen Colletotrichum gloeosporioides isolate Cg-14 (teleomorph: Glomerella cingulata) were generated by insertional mutagenesis by restriction enzyme-mediated integration (REMI) transformation. Following seven transformations, 3,500 hygromycin-resistant isolates were subjected to a virulence assay by inoculation on mesocarp and pericarp of cv. Fuerte avocado fruits. Fourteen isolates showed a reduced degree of virulence relative compared with wild-type Cg-14. Two isolates, Cg-M-142 and Cg-M-1150, were further characterized. Cg-M-142 produced appressoria on avocado pericarp similar to Cg-14, but caused reduced symptom development on the fruit's pericarp and mesocarp. Isolate Cg-M-1150 did not produce appressoria; it caused much reduced maceration on the mesocarp and no symptoms on the pericarp. Southern blot analysis of Cg-M-142 and Cg-M-1150 showed REMI at different XbaI sites of the fungal genome. Pre-inoculation of avocado fruit with Cg-M-142 delayed symptom development by the wild-type isolate. Induced resistance was accompanied by an increase in the levels of preformed antifungal diene, from 760 to 1,200 μg/g fresh weight 9 days after inoculation, whereas pre-inoculation with Cg-M-1150 did not affect the level of antifungal diene, nor did it delay the appearance of decay symptoms. The results presented here show that reduced-pathogenicity isolates can be used for the biological control of anthracnose caused by C. gloeosporioides attack.

scholarly journals Differential Activation of Ammonium Transporters During the Accumulation of Ammonia by Colletotrichum gloeosporioides and Its Effect on Appressoria Formation and Pathogenicity

2013 ◽  
Vol 26 (3) ◽  
pp. 345-355 ◽  
Author(s):  
Chen Shnaiderman ◽  
Itay Miyara ◽  
Ilana Kobiler ◽  
Amir Sherman ◽  
Dov Prusky
Keyword(s):  
Gene Disruption ◽  
Colletotrichum Gloeosporioides ◽  
Ammonium Transporter ◽  
Ammonium Transport ◽  
Wild Type ◽  
Ammonia Accumulation ◽  
Ammonium Transporters ◽  
Avocado Fruit ◽  
Appressoria Formation ◽  
Encoding Genes

Ammonium secreted by the post-harvest pathogen Colletotrichum gloeosporioides during host colonization accumulates in the host environment due to enhanced fungal nitrogen metabolism. Two types of ammonium transporter-encoding genes, AMET and MEP, are expressed during pathogenicity. Gene disruption of AMET, a gene modulating ammonia secretion, showed twofold reduced ammonia secretion and 45% less colonization on avocado fruit, suggesting a contribution to pathogenicity. MEPB, a gene modulating ammonium transport, is expressed by C. gloeosporioides during pathogenicity and starvation conditions in culture. Gene disruption of MEPB, the most highly expressed gene of the MEP family, resulted in twofold overexpression of MEPA and MEPC but reduced colonization, suggesting MEPB expression's contribution to pathogenicity. Analysis of internal and external ammonia accumulation by ΔmepB strains in mycelia and germinated spores showed rapid uptake and accumulation, and reduced secretion of ammonia in the mutant versus wild-type (WT) strains. Ammonia uptake by the WT germinating spores but not by the ΔmepB strain with compromised ammonium transport activated cAMP and transcription of PKA subunits PKAR and PKA2. ΔmepB mutants showed 75% less appressorium formation and colonization than the WT, which was partially restored by 10 mM exogenous ammonia. Thus, whereas both AMET and MEPB genes modulate ammonia secretion, only MEPB contributes to ammonia accumulation by mycelia and germinating spores that activate the cAMP pathways, inducing the morphogenetic processes contributing to C. gloeosporioides pathogenicity.

scholarly journals Inheritance of extrachromosomal ribosomal DNA during the asexual life cycle of Dictyostelium discoideum: examination by use of DNA polymorphisms.

1985 ◽  
Vol 5 (2) ◽  
pp. 273-280 ◽  
Author(s):  
D L Welker ◽  
K P Hirth ◽  
K L Williams
Keyword(s):  
Life Cycle ◽  
Dictyostelium Discoideum ◽  
Ribosomal Dna ◽  
Dna Polymorphisms ◽  
Haploid Cell ◽  
Wild Type ◽  
Parasexual Cycle ◽  
Restriction Fragments ◽  
Type Isolate ◽  
Ca 50

Wild-type isolates of Dictyostelium discoideum exhibited differences in the size of restriction fragments of the extrachromosomal 88-kilobase ribosomal DNA (rDNA) palindrome. Polymorphisms in rDNA also were found among strains derived solely from the NC4 wild-type isolate. These variations involved EcoRI fragments II, III, and V; they included loss of the EcoRI site separating fragments II and V and deletion and insertion of DNA. More than one rDNA form can coexist in the same diploid or haploid cell. However, one or another parental rDNA tended to predominate in diploids constructed, using the parasexual cycle, between haploid NC4-derived strains and haploid wild-type isolates. In some cases, most if not all of the rDNA of such diploids were of one form after ca. 50 generations of growth. Segregant haploids, derived from diploids that possessed predominantly a single rDNA allele, possessed the same allele as the diploid and did not recover the other form. This evidence implies that replication does not proceed from a single chromosomal or extrachromosomal copy of the rDNA during the asexual life cycle of D. discoideum.

scholarly journals Colletotrichum gloeosporioides pelB Is an Important Virulence Factor in Avocado Fruit-Fungus Interaction

2001 ◽  
Vol 14 (8) ◽  
pp. 988-995 ◽  
Author(s):  
Nir Yakoby ◽  
Delila Beno-Moualem ◽  
Noel T. Keen ◽  
Amos Dinoor ◽  
Ophry Pines ◽  
...  
Keyword(s):  
Virulence Factor ◽  
Defense Mechanisms ◽  
Phenylalanine Ammonia Lyase ◽  
Colletotrichum Gloeosporioides ◽  
Pectate Lyase ◽  
Wild Type ◽  
Avocado Fruit ◽  
Lyase Activity ◽  
Important Virulence Factor ◽  
Phenylalanine Ammonia Lyase Activity

Colletotrichum gloeosporioides is an important pathogen of tropical and subtropical fruits. The C. gloeosporioides pelB gene was disrupted in the fungus via homologous recombination. Three independent isolates, GD-14, GD-23, and GD-29, did not produce or secrete pectate lyase B (PLB) and exhibited 25% lower pectate lyase (PL) and pectin lyase (PNL) activities and 15% higher polygalacturonase (PG) activity than the wild type. The PLB mutants exhibited no growth reduction on glucose, Na polypectate, or pectin as the sole carbon source at pH 3.8 or 6.0, except for a 15% reduction on pectin at pH 6.0. When pelB mutants were inoculated onto avocado fruits, however, a 36 to 45% reduction in estimated decay diameter was observed compared with the two controls, the wild type and undisrupted transformed isolate. In addition, these pelB mutants induced a significantly higher host phenylalanine ammonia lyase activity as well as the antifungal diene, which is indicative of higher host resistance. These results suggest that PLB is an important factor in the attack of C. gloeosporioides on avocado fruit, probably as a result of its virulence factor and role in the induction of host defense mechanisms.

Potential for biological control of Cercosporidium personatum leafspot of peanuts by Dicyma pulvinata

1987 ◽  
Vol 65 (11) ◽  
pp. 2263-2269 ◽  
Author(s):  
James K. Mitchell ◽  
Donald H. Smith ◽  
Ruth A. Taber
Keyword(s):  
Biological Control ◽  
Environmental Conditions ◽  
Field Conditions ◽  
Leaf Wetness ◽  
Wild Type ◽  
Cercosporidium Personatum ◽  
Type Isolate ◽  
65 H

The biology of Dicyma pulvinata (Berk. & Curt.) v. Arx, a mycoparasite of Cercosporidium personatum (Berk. & Curt.) Deighton, was investigated under both laboratory and field conditions. At 26 °C, conidia of D. pulvinata close to both hyphae and conidia of C. personatum germinated within 11–17 h. Visible signs of colonization of lesions of C. personatum by D. pulvinata appeared within 58–65 h (21–31.5 h leaf wetness). Dicyma pulvinata was an effective protectant when plants were exposed to continuous leaf wetness at 26 °C for 5 days. In field microplot studies, lesions of C. personatum were visibly colonized by both mutant and wild-type isolates of D. pulvinata within 4 days after applying their conidial suspensions. Environmental conditions during this 4-day period were 40 h leaf wetness, 60 h of 23–28 °C (optimal temperatures for growth of the wild-type isolate), and 17.31 cm rainfall.

Inheritance of extrachromosomal ribosomal DNA during the asexual life cycle of Dictyostelium discoideum: examination by use of DNA polymorphisms

1985 ◽  
Vol 5 (2) ◽  
pp. 273-280
Author(s):  
D L Welker ◽  
K P Hirth ◽  
K L Williams
Keyword(s):  
Life Cycle ◽  
Dictyostelium Discoideum ◽  
Ribosomal Dna ◽  
Dna Polymorphisms ◽  
Haploid Cell ◽  
Wild Type ◽  
Parasexual Cycle ◽  
Restriction Fragments ◽  
Type Isolate ◽  
Ca 50

Wild-type isolates of Dictyostelium discoideum exhibited differences in the size of restriction fragments of the extrachromosomal 88-kilobase ribosomal DNA (rDNA) palindrome. Polymorphisms in rDNA also were found among strains derived solely from the NC4 wild-type isolate. These variations involved EcoRI fragments II, III, and V; they included loss of the EcoRI site separating fragments II and V and deletion and insertion of DNA. More than one rDNA form can coexist in the same diploid or haploid cell. However, one or another parental rDNA tended to predominate in diploids constructed, using the parasexual cycle, between haploid NC4-derived strains and haploid wild-type isolates. In some cases, most if not all of the rDNA of such diploids were of one form after ca. 50 generations of growth. Segregant haploids, derived from diploids that possessed predominantly a single rDNA allele, possessed the same allele as the diploid and did not recover the other form. This evidence implies that replication does not proceed from a single chromosomal or extrachromosomal copy of the rDNA during the asexual life cycle of D. discoideum.

scholarly journals CHROMOSOMAL BASIS OF THE MEROZYGOSITY IN A PARTIALLY DIPLOID MUTANT OF PNEUMOCOCCUS

Genetics ◽  
1975 ◽  
Vol 80 (4) ◽  
pp. 667-678
Author(s):  
Mary Lee S Ledbetter ◽  
Rollin D Hotchkiss
Keyword(s):  
High Efficiency ◽  
Point Mutations ◽  
Resistant Mutant ◽  
Chromosomal Marker ◽  
Structural Abnormality ◽  
C Cells ◽  
Wild Type ◽  
Chromosomal Locus ◽  
Low Efficiency ◽  
Derivatives Of

ABSTRACT A sulfonamide-resistant mutant of pneumococcus, sulr-c, displays a genetic instability, regularly segregating to wild type. DNA extracts of derivatives of the strain possess transforming activities for both the mutant and wild-type alleles, establishing that the strain is a partial diploid. The linkage of sulr-c to strr-61, a stable chromosomal marker, was established, thus defining a chromosomal locus for sulr-c. DNA isolated from sulr-c cells transforms two mutant recipient strains at the same low efficiency as it does a wild-type recipient, although the mutant property of these strains makes them capable of integrating classical "low-efficiency" donor markers equally as efficiently as "high efficiency" markers. Hence sulr-c must have a different basis for its low efficiency than do classical low efficiency point mutations. We suggest that the DNA in the region of the sulr-c mutation has a structural abnormality which leads both to its frequent segregation during growth and its difficulty in efficiently mediating genetic transformation.

scholarly journals Engineered Phage Endolysin Eliminates Gardnerella Biofilm without Damaging Beneficial Bacteria in Bacterial Vaginosis Ex Vivo

Pathogens ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 54
Author(s):  
Christine Landlinger ◽  
Lenka Tisakova ◽  
Vera Oberbauer ◽  
Timo Schwebs ◽  
Abbas Muhammad ◽  
...  
Keyword(s):  
Bacterial Vaginosis ◽  
Bactericidal Activity ◽  
High Selectivity ◽  
Ex Vivo ◽  
Vaginal Microbiome ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Promising Alternative ◽  
First Time

Bacterial vaginosis is characterized by an imbalance of the vaginal microbiome and a characteristic biofilm formed on the vaginal epithelium, which is initiated and dominated by Gardnerella bacteria, and is frequently refractory to antibiotic treatment. We investigated endolysins of the type 1,4-beta-N-acetylmuramidase encoded on Gardnerella prophages as an alternative treatment. When recombinantly expressed, these proteins demonstrated strong bactericidal activity against four different Gardnerella species. By domain shuffling, we generated several engineered endolysins with 10-fold higher bactericidal activity than any wild-type enzyme. When tested against a panel of 20 Gardnerella strains, the most active endolysin, called PM-477, showed minimum inhibitory concentrations of 0.13–8 µg/mL. PM-477 had no effect on beneficial lactobacilli or other species of vaginal bacteria. Furthermore, the efficacy of PM-477 was tested by fluorescence in situ hybridization on vaginal samples of fifteen patients with either first time or recurring bacterial vaginosis. In thirteen cases, PM-477 killed the Gardnerella bacteria and physically dissolved the biofilms without affecting the remaining vaginal microbiome. The high selectivity and effectiveness in eliminating Gardnerella, both in cultures of isolated strains as well as in clinically derived samples of natural polymicrobial biofilms, makes PM-477 a promising alternative to antibiotics for the treatment of bacterial vaginosis, especially in patients with frequent recurrence.

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