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J M Manners

Publications and source records attributed to J M Manners.

At least 37 records · Page 2Linked to original sources
PubMed1996

CgT1: a non-LTR retrotransposon with restricted distribution in the fungal phytopathogen Colletotrichum gloeosporioides.

Two genetically distinct biotypes (A and B) of Colletotrichum gloeosporioides that cause different anthracnose diseases on the legumes Stylosanthes spp. have been identified in Australia. A DNA sequence that was present in biotype B and absent in biotype A was isolated by differential hybridisation of a genomic library using total genomic DNA of each biotype as hybridisation probes. This sequence also failed to hybridise to DNA of three biotypes of C. gloeosporioides from other host species and to DNA of three other species of Colletotrichum. This clone was used to isolate two cosmid clones of biotype B. Sequence analysis of these clones revealed a repetitive element of approximately 5.7 kb in length. This element, termed CgT1, was dispersed in the genome and present in about 30 copies. The element contained open reading frames encoding deduced sequence motifs homologous to gag-like proteins, reverse transcriptase and RNase H domains of non-LTR retrotransposons. The termini of CgT1 lacked long terminal repeats (LTRs) but contained a 3' A-rich domain. The insertion site of one copy of the element was flanked by short 13-bp direct repeats. These characteristics of the termini, taken together with the overall structure and sequence homologies, indicate that CgT1 belongs to the non-LTR, LINE-like retrotransposon class of elements that are present in many eukaryotes. PCR primers designed to amplify regions of CgT1 can be used to distinguish biotypes A and B in Australia. DNA fingerprinting analysis of genomic DNA using hybridisation probes derived from the terminal regions of CgT1 revealed that Australian isolates of biotype B are monomorphic. CgT1 was not detected in some isolates causing Type B disease from other countries and when CgT1 was present there was considerable polymorphism in CgT1 organisation in the genome. CgT1 is the first transposon-like element to be identified in the genus Colletotrichum and has considerable potential as a tool for the study of population structure, genome dynamics and evolution in C. gloeosporioides.

Amino Acid Sequence↗
PubMed1996

Strategies for the suppression of peroxidase gene expression in tobacco. I. Designing efficient ribozymes.

Five short hammerhead ribozymes (Rzs) were constructed and tested, using a range of in vitro reaction conditions, for catalytic activity against the mRNA encoding the lignin-forming peroxidase (TPX) of tobacco. Although all 5 Rzs were shown to be able to cleave the RNA substrate, percentage cleavage varied with pre-denaturation of Rz and substrate, incubation temperature, length of incubation and ribozyme (Rz)-to-substrate ratio. One Rz with two catalytic units and 60 nucleotides of complementary sequence in 3 regions was shown to most efficiently cleave the substrate under all in vitro conditions tested. This ribozyme cleaved better than the two single ribozymes from which it was made. The superior cleaving ability of this Rz was shown to be due to the accessibility of the chosen target site and to the increased length of the hybridizing arms spanning this accessible region of the RNA.

Amino Acid Sequence↗
PubMed1996

Strategies for the suppression of peroxidase gene expression in tobacco. II. In vivo suppression of peroxidase activity in transgenic tobacco using ribozyme and antisense constructs.

Several strategies involving the use of antisense and ribozyme constructs in different expression vectors were investigated as methods of suppressing gene expression in planta. We had previously identified an efficiently cleaving ribozyme (Rz), with two catalytic units and 60 nucleotide (nt) of complementary sequence, to the lignin-forming peroxidase of tobacco (TPX). This Rz was cloned behind the 35S CaMV (35S) and nopaline synthase (NOS) promoters, and into a vector utilising the tobacco tyrosine tRNA for expression. For comparison with more traditional antisense strategies, full-length TPX antisense (AS) constructs were also constructed behind the NOS and 35S promoters. Populations of transgenic tobacco containing these constructs were produced and compared to control plants transformed with the vector only. Significant suppression of peroxidase expression in the range of 40-80% was seen in the T0 and T1 populations carrying 35S-AS, 35S-Rz and tRNA-Rz constructs. Co-segregation of the suppressed peroxidase phenotype and the tRNA-Rz transgenes was demonstrated. Northern blot analysis indicated that levels of TPX mRNA were lower in the Rz plants. No evidence of mRNA cleavage was observed and thus it was unclear if the Rz constructs were acting as Rzs in vivo. Transgenic plants containing the tRNA-Rz construct had significantly lower levels of peroxidase than the other transgenic plants. There was no significant difference in levels of suppression of TPX between the short Rz in the 35S vector and the full-length AS constructs. Although peroxidase levels were significantly reduced in transgenic plants carrying 35S-AS, 35S-Rz and tRNA-Rz constructs, no significant difference in lignin levels was observed.

Agrobacterium tumefaciens↗
PubMed1996

Pathogen-induced systemic activation of a plant defensin gene in Arabidopsis follows a salicylic acid-independent pathway.

A 5-kD plant defensin was purified from Arabidopsis leaves challenged with the fungus Alternaria brassicicola and shown to possess antifungal properties in vitro. The corresponding plant defensin gene was induced after treatment of leaves with methyl jasmonate or ethylene but not with salicylic acid or 2,6-dichloroisonicotinic acid. When challenged with A. brassicicola, the levels of the plant defensin protein and mRNA rose both in inoculated leaves and in nontreated leaves of inoculated plants (systemic leaves). These events coincided with an increase in the endogenous jasmonic acid content of both types of leaves. Systemic pathogen-induced expression of the plant defensin gene was unaffected in Arabidopsis transformants (nahG) or mutants (npr1 and cpr1) affected in the salicylic acid response but was strongly reduced in the Arabidopsis mutants eln2 and col1 that are blocked in their response to ethylene and methyl jasmonate, respectively. Our results indicate that systemic pathogen-induced expression of the plant defensin gene in Arabidopsis is independent of salicylic acid but requires components of the ethylene and jasmonic acid response.

Alternaria↗
PubMed1993

A strain-specific cyclin homolog in the fungal phytopathogen Colletotrichum gloeosporioides.

The fungus, Colletotrichum gloeosporioides, which infects the tropical pasture legume, Stylosanthes guianensis, contains highly variable mini-chromosomes. The transcription of strain-specific genomic DNA clones previously isolated from one variable mini-chromosome was investigated by using these clones to screen a cDNA library prepared from the fungus grown in liquid medium. A cDNA clone was obtained with one of the genomic clones and was sequenced. A single long open reading frame of 259 amino acids (aa) was detected with significant homology to cyclin proteins in other organisms. Northern blot analysis indicated that the cDNA corresponded to a low-abundance mRNA (approximately 0.001% of poly(A)+RNA). Southern blot analysis indicated that genes encoding this mRNA were discontinuously distributed in this fungal species, indicating it encodes a dispensable function. This result suggests that natural populations of fungi may have variable complements of cyclin-encoding genes.

Amino Acid Sequence↗
PubMed1993

Characterization of an endo-1,3(4)-beta-D-glucanase gene from Cellvibrio mixtus.

An endo-1,3(4)-beta-D-glucanase gene (cwd2) of Cellvibrio mixtus encoding laminarinase activity was cloned on a 3.9-kb PstI fragment. The Cwd2 enzyme, extracted from recombinant Escherichia coli, degraded both beta-1,3 glucans and beta-1,3-1,4 mixed-linkage glucans, was endohydrolytic and so conformed to the enzyme class 3.2.1.6. The pH and temperature optima of the enzyme were approximately 7 and 40 degrees C respectively. The M(r) of specifically labelled Cwd2 was approximately 34,000. This gene was quite distinct from two other C. mixtus beta-1,3 glucanases previously described.

Chromatography, Thin Layer↗
PubMed1993

DNA addition or deletion is associated with a major karyotype polymorphism in the fungal phytopathogen Colletotrichum gloeosporioides.

A 1.2 Mb minichromosome resolved by pulsed-field electrophoresis was present in two independent race 3 isolates of Colletotrichum gloeosporioides causing Type B anthracnose specifically on Stylosanthes guianensis cv. Graham in Australia. This chromosome was absent in duplicate isolates representing races 1, 2 and 4 which infect other S. guianensis cultivars. A gene library was prepared specifically from the 1.2 Mb minichromosome and ten independent DNA clones unique to this chromosome were identified by differential hybridisation to whole chromosome probes. All of the ten selected probes hybridised only to the 1.2 Mb minichromosome unique to the race 3 isolates but not to any chromosome in isolates of the other races. These ten probes also hybridised only to restriction-digested DNA of race 3 and were thus both chromosome- and strain-specific for Type B C. gloeosporioides. Hybridisation analysis of NotI fragments of the 1.2 Mb minichromosome with these sequences indicated that they were not tightly clustered on the chromosome. These data demonstrate that the variation in the occurrence of the 1.2 Mb minichromosome did not arise by rearrangement of the genome of a progenitor strain but involved either large scale deletion or addition of DNA. The 1.2 Mb minichromosome did not contain a cloned high-copy-number repeat sequence present on all other mini- and maxichromosomes, suggesting addition from a genetically distinct strain. All ten chromosome-specific DNA probes hybridised to a 2.0 Mb chromosome in all races of C. gloeosporioides causing Type A anthracnose on Stylosanthes spp. including S. guianensis.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromosome Aberrations↗
PubMed1993

Random amplified polymorphic DNA markers reveal a high degree of genetic diversity in the entomopathogenic fungus Metarhizium anisopliae var. anisopliae.

Metarhizium anisopliae isolates from several insect hosts and from various sugar cane growing areas of Queensland, Australia, were examined for genetic diversity using random amplified polymorphic DNA (RAPD) markers. Thirty isolates of M. anisopliae var. anisopliae and one isolate of M. anisopliae var. majus were examined. Ten randomly chosen 10mer or 11mer primers were used and RAPD banding patterns were compared. Thirty distinct genotypes could be distinguished amongst the 31 isolates tested on the basis of RAPD patterns. Six of the isolates classified as M. anisopliae var. anisopliae exhibited closer similarity to the M. anisopliae var. majus isolate than to other anisopliae strains tested. Isolates exhibiting similar (> 80% similarity) RAPD profiles tended to be isolated from the same geographic area and evidence for the persistence of particular fungal genotypes in specific geographical localities was obtained. Pathogenicity assays suggested that, in some instances, RAPD groupings may also indicate insect host range. The mean similarity amongst isolates measured by band sharing in all pairwise comparisons was 41% and the most distinct pair of isolates shared only 9% of their RAPD bands. We conclude that the isolates tested belonging to the species M. anisopliae, as assessed on morphological grounds, represent a very diverse genetic group. The results also suggest that RAPD markers may be useful for the tracking of specific biocontrol strains in the field.

Animals↗
PubMed1993

Genetic relationships and variation in the Stylosanthes guianensis species complex assessed by random amplified polymorphic DNA.

Genetic variation in the five taxonomic groups of the Stylosanthes guianensis (Aubl.) Sw. complex was investigated using random amplified polymorphic DNA markers (RAPDs). DNA samples from four plants of each of 45 accessions within the S. guianensis species complex were analyzed using 20 oligonucleotides of random sequence. Little variation was found within each of the 18 accessions (1-7% of total RAPD bands in pairwise comparisons) and none within each of the other 27 accessions. However, higher levels of polymorphisms were observed both within (index of genetic distance = 1 - F = 0.16-0.248) and between (1 - F = 0.254-0.408) the five taxa. This level of differentiation at the DNA level supported an earlier classification of the taxa as distinct species. A phenogram based on band sharing was constructed to show genetic relationships among the taxa studied. This phenogram corroborated the description of relationships based on morphological-agronomic characteristics, seed protein patterns, rhizobial affinities, crossability, and pollen stainability of the hybrids. In this phenogram, the most similar species were S. grandiflora and S. hippocampoides (1 - F = 0.264), with S. acuminata also showing closest similarity to these two species (1 - F = 0.277 and 0.283, respectively). Stylosanthes gracilis accessions showed the closest similarity (1 - F = 0.296) to S. guianensis ssp. guianensis accessions. Lowest similarity values (1 - F = 0.335-0.411) were found between these two species and S. grandiflora, S. acuminata, and S. hippocampoides.

Base Sequence↗