Robert Jeng

Isolation and characterization of the cerato-ulmin toxin gene of the Dutch elm disease pathogen, Ophiostoma ulmi

The hydrophobic protein cerato-ulmin (CU), produced by Ophiostoma ulmi, has been implicated in the pathogencity of this fungus on elm. Primers were designed based on the nucleotide sequence deduced from the published CU amino-acid sequence, and a DNA fragment of the cu gene was amplified using the polymerase chain reaction. The amplified cu fragment was used as a hybridization probe to identify and isolate the cu gene from a genomic DNA library of an aggressive isolate of O. ulmi (= O. novo-ulmi). The cu coding region is interrupted by two introns and encodes a 100 amino-acid prepro-CU polypeptide that is processed to a 75 amino-acid mature protein upon secretion. CU shows significant sequence similarity to hydrophobins secreted by certain other fungi.

Identification of three populations ofOphiostoma ulmi (aggressive subgroup) by mitochondrial DNA restriction-site mapping and nuclear DNA fingerprinting

Three genetically distinct populations of the Dutch elm pathogenOphistoma ulmi within the aggressive subgroup were defined by the hybridization of a human minisatellite DNA sequence (HVR 33.6) to polymorphic dispersed DNA sequences within theO. ulmi nuclear genomes. For the 10 isolates examined there was a close correlation between nuclear DNA fingerprints and mitochondrial (mt) DNA restriction patterns. A restriction-site map was constructed for the mitochondrial genomes for each of these populations. The three mt DNA maps corresponded to genome sizes of 49.1 (Type I), 49.9 (Type II), and 53.9 (Type III) kilobase pairs (kbp) of DNA. The Type I and Type II mt genomes differed from the Type III mt genome by discrete length mutations of 4.8 and 4.0 kbp, respectively. It is unknown whether these length mutations resulted from insertions into or deletions from a progenitor mitochondrial genome. There was no correlation between the mitochondrial or nuclear genotypes and the geographical source of the isolates.

DNA analysis of Cylindrocladium floridanum isolates from selected forest nurseries

Isolates of Cylindrocladium floridanum obtained from diseased roots of white and black spruce seedlings and surrounding soil in bareroot nurseries in Ontario, Minnesota and Wisconsin area were compared by mitochondrial DNA (mtDNA) and ribosomal DNA (rDNA) restriction fragment length polymorphisms (RFLPs), human minisatellite DNA fingerprints and polymerase chain reaction. Nucleotide sequences of rDNA ITS regions of selected isolates were also performed. Based on the nuclear DNA fingerprinting patterns, these isolates could be divided into three groups, namely S1, S2 and S3. Isolates of S1 and S2 showed the same mtDNA RFLPs which were slightly different from that of S3. Isolates representing each of the three groups showed an identical nucleotide sequence of rDNA ITS regions. These data suggest that all the isolates tested belong to the same species which may be divided into three biotypes or populations.

A comparison of the nucleotide sequence of the cerato-ulmin gene and the rDNA ITS between aggressive and non-aggressive isolates ofOphiostoma ulmi sensu lato, the causal agent of Dutch elm disease

Little genetic information exists comparing aggressive and non-aggressive isolates of the causal agent of Dutch elm disease,Ophiostoma ulmi. Two genetic elements were compared between the subgroups. The ceratoulmincu gene product has been associated with disease symptoms. Nucleotide-sequence analysis ofcu and the internal transcribed spacer (ITS) region of the rDNA were made from three aggressive and three non-aggressive isolates of the pathogen. Our results suggested uniformity within, and unique differences between, subgroups. Differences were detected forcu in the promoter, coding, and transcription termination regions. Sequence data for the ITS clearly distinguish the subgroups.

Production of value-added chemicals from wheat straw lignin by bio-refinery process

Lignocellulosic-based bio-refineries are essential for a secure energy in future. Lignin degradation is required for carbon recycling and production of renewable chemicals. Lignin due to the high level of color and low biodegradability, is categorized as a serious pollutant particularly in the aquatic ecosystem. In this study, biodegradation of organosolv lignin by a white rot fungi, Bjerkandera adusta, was verified. The FTIR spectra of lignin, before and after treatment with fungi displayed modification by changing in the structure of lignin. Some of the functional groups have disappeared and some new bands appeared in the spectra. The SDS-PAGE chromatographs also showed that the fungi protein has a molecular weight of 44 kDa. This molecular weight increased to 46 kDa after the treatment of lignin by fungi. The heavier molecular weight occurred due to the bonding of fungi protein with lignin. The results from surface morphology also showed the attachments of lignin molecules to fungi mycelia. As a result, the extracted lignin after treatment with B. adusta showed significant changes in its physical and chemical structure which makes it a noble candidate for carrying out value added products and refinery of lignin waste in pulp and paper industries.