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D A Gaudet

Publications and source records attributed to D A Gaudet.

5 recordsLinked to original sources
PubMed2000

Production of cellulases and xylanases by low-temperature basidiomycetes.

Three of four isolates, representing phylogenetically distinct groupings of low-temperature basidiomycetes (LTB), were capable of utilizing wheat straw, and to a lesser extent conifer wood at 15 degrees C. A cottony snow mould LTB (LRS 013) and a fruit rot LTB (LRS 241) grown on straw significantly degraded filter paper, carboxymethylcellulose (CMC), p-nitrophenyl beta-glucopyranoside (i.e., beta-glucosidases), and xylan. Enzymes produced by Coprinus psychromorbidus (LRS 067) were limited to xylanases from straw and wood and beta-glucosidases from wood. A sclerotia-forming LTB (LRS 131) exhibited poor growth on both substrates, and did not produce detectable quantities of extracellular enzymes. None of the LTB isolates tested degraded avicel. The temperature optima of CMCases and xylanases in the filtrates from the straw medium ranged from 25 degrees C to 55 degrees C, and with the exception of LRS 067, significant activity was observed at 5 degrees C. Two cellulases (25 and 31 kDa) and two xylanases (24 and 34 kDa) were observed on zymograms for LRS 013 and 241. Reduction of enzymes with 2-mercaptoethanol adversely affected their activity on zymograms, and an additional cellulase band was observed for non-reduced samples. This study indicates that LTB produce an array of cellulolytic and xylanolytic enzymes, and that some of these enzymes possess low-temperature optima which may facilitate degradation of plant fibre under low-temperature conditions.

Basidiomycota↗
PubMed2000

Development of a PCR marker for rapid identification of the Bt-10 gene for common bunt resistance in wheat.

In western Canada, the Bt-10 resistance gene in wheat (Triticum aestivum) is effective against all the known races of common bunt caused by Tilletia tritici and T laevis. The genotypes of 199 F2 plants, originated from a cross between BW553 containing Bt-10 and the susceptible spring wheat cultivar 'Neepawa,' were established in greenhouse and field inoculation studies. A ratio of 1:2:1 resistant : heterozygous : susceptible was observed for bunt reaction, indicating that Bt-10 was expressed in a partially dominant fashion. A polymorphic DNA fragment, amplified using RAPD, and previously shown to be linked to Bt-10 was sequenced and SCAR (sequence characterized amplified region) primers devised. However, SCAR primers failed to amplify the polymorphic fragment. Restriction of PCR products with DraI revealed a polymorphic fragment of 490 bp resulting from a single base pair difference between lines possessing Bt-10 and those lacking the gene. As per the base pair difference, FSD and RSA primers were designed to generate a 275-bp polymorphic DNA fragment. Both 275- and 490-bp polymorphic fragments were present in all of the 22 cultivars known to carry Bt-10, and absent in all 16 cultivars lacking Bt-10. A 3:1 ratio was observed for presence: absence of the 275-bp marker in the F2 population. Using Southern analysis, the 490-bp fragment was effective in differentiating homozygous resistant plants from those heterozygous for Bt-10, based on its presence and the hybridization signal strength. A 1:2:1 resistant : heterozygous : susceptible ratio was also observed for the molecular marker and corresponded to 88% of the phenotypes deduced from the original F2 population. The molecular marker was estimated to be between 1.1 cM and 6.5 cM away from the Bt-10 resistance gene, based on the segregation analysis. Segregation analyses of Bt-10 and the 275-bp marker, evaluated in three different Canada Prairie Spring (CPS) wheat populations, demonstrated a segregation ratio of 3:1 for the molecular marker in two of the populations. These results demonstrated that the PCR marker system using the FSD and RSA primer pair permitted a rapid and reliable identification of individual lines carrying the Bt-10 gene for resistance to common bunt.

Blotting, Southern↗
PubMed1998

Origins and inheritance of chromosome-length polymorphisms in the barley covered smut fungus, Ustilago hordei.

Numerous chromomsome-length polymorphisms (CLPs) associated with chromosome IV were detected in an inbred line of race 8 of Ustilago hordei (teliospore line 1279). Polymorphisms for chromosome IV were observed in the 1600-1900-kb range in approximately 8% of the haploid sporidia originating from this teliospore collection. A monosporidial strain, 1279Ca2, exhibited a new 1620-kb chromosome band and a concurrent loss of the 1950-kb chromosome IV. A ribosomal DNA probe from Armillaria mellea specifically hybridized to both the variant 1620-kb chromosome and to the 1950-kb rDNA chromosome IV in parental strains. Following digestion of chromosome IV with HinfI, the telomere fragments of the 1620-kb chromosome were similar to those of the 1950-kb chromosome IV, indicating that the 1620-kb chromosome arose following a deletion of approximately 330 kb from chromosome IV. The Hinf1 digest of chromosome IV, when probed with the rDNA probe, revealed that much of the rDNA of chromosome IV was lost in the 1279Ca2 line. rDNA sequences were coincidentally recorded in chromosomes I and II in the sister sporidial line, 1279Ca4. When the 1279Ca2 line was mated to other members within the same tetrad and inoculated onto susceptible barley, karyotypes of tetrads and random sporidia originating from the F1 progeny possessed variant chromosomes ranging in size from 1536 to 2110 kb. Among sporidia in 5 of the 12 ordered tetrads sampled, a 1:1 ratio of the 1950-kb parental chromosome IV to the variant chromosome was observed. Within these tetrads, the two polymorphic chromosomes were identical in size and larger than that of the original variant 1620-kb chromosome suggesting that a chromosome expansion, averaging 150 kb, had occurred. In 5 of the 12 tetrads, a 1:1:1:1 ratio representing the two original parents and two recombinant chromosomes was observed, suggesting that normal or unequal recombination had occurred during meiosis. In 2 of the 12 F1 progeny tetrads, the 1950-kb chromosome IVs were apparently eliminated. In karyotypes of these sporidial lines, we observed rDNA sequences in chromosomes I and III that were translocated from chromosome IV. Among 78 random sporidia in the F1 generation, duplication of the variant chromosome IV was observed in three strains. These results suggest that polymorphisms in the rDNA chromosome IV, which consist of chromosome expansion, translocation, and chromosome elimination or duplication, are common in the 1279 strain of U. hordei and its progeny, and that this variability appears to be associated with the tandem-repeat nature of the rDNA sequences.

Chromosome Deletion↗
PubMed1996

A DNA marker for the Bt-10 common bunt resistance gene in wheat.

The Bt-10 bunt gene confers resistance to most races of the common bunt fungi, Tilletia tritici and T. laevis. The RAPD technique, employing a total of 965 decamer primers, was used to identify polymorphic markers between resistant (BW553) and susceptible ('Neepawa") near-isogenic lines. Primer 196 (5' CTC CTC CCC C 3') produced a 590 base pair (bp) reproducible fragment only in the resistant near-isogenic line. The 590-bp DNA fragment was present in all the 22 wheat cultivars known to carry the Bt-10 resistance gene and also in 15 resistant F2 lines obtained from a cross between the resistant parent, BW553, and the susceptible parent, 'Neepawa'. The 590-bp fragment was absent in 16 susceptible cultivars tested and in 15 susceptible F2 lines obtained from the cross described above. These results suggest a close linkage between the presence of the 590-bp fragment and the Bt-10 resistance gene. Primer 372 (5' CCC ACT GAC G 3') amplified a 1.0-kilobase (kb) fragment that was present only in the susceptible near-isogenic line. This 1.0-kb fragment was present in 13 of the 16 susceptible cultivars and in 13 of the 15 susceptible F2 lines. However, the primer also amplified the 1.0-kb fragment in some resistant cultivars and resistant F2 lines, suggesting a looser linkage between the occurrence of the fragment and the susceptible allele.

Base Sequence↗