Variability in genome organization of the zygomycete Parasitella parasitica

Molecular characterization of Mucor circinelloides and Rhizopus stolonifer strains isolated from some saudi fruits

Thirteen strains of Mucor circinelloides and nine strains of Rhizopus stolonifer were collected from different Saudi fruits. Also, two strains of M. circinelloides and one strain of R. stolonifer isolated from soil were used in this study to analyze the genetic diversity among these 25 strains. The dendrogram constructed from random amplified polymorphic DNA-polymerase chain reaction results using two primers (V6 and M13) showed no correlation between clustering system and sources of isolation for M. circinelloides strains, while Rhizopus strains clustered according to the sources of isolation. The phylogenetic tree based on the unweighted pair group method with arithmetic average of internal transcribed spacer (ITS) rDNA sequence revealed the variation of the ITS region among Mucor strains as well as Rhizopus strains.

Genotypic analysis of variability in Zygomycetes. A mini-review

Different types of molecular markers are available for use in evolutionary and population studies of microscopic fungi. These approaches have proved their merits and have been successfully applied to a wide range of fungal species belonging in the Ascomycetes and Basidiomycetes. Species in the class Zygomycetes have been rather neglected from this aspect. This review discusses the information available from investigations of the genotypic variability in this group of fungi.

Sexuality and parasitism share common regulatory pathways in the fungus Parasitella parasitica

Parasitella parasitica, a facultative mycoparasite of zygomycetous fungi, forms cytoplasmic fusions with its hosts during infection. Thus, the organism is an efficient donor of genetic material in parasexual host-parasite interactions. Recognition between parasite and host is mediated by trisporoids, which are also responsible for sexual communication. The TDH gene for one of the key enzymes of trisporic acid biosynthesis, 4-dihydromethyl-trisporate dehydrogenase, was cloned and its transcription analysed. TDH was cloned on a 6175-bp insert and was found to map in a complex cluster of genes that suggest post-transcriptional antisense regulation. Histochemical TDH analysis in developing parasitic or sexual structures shows high enzymatic activity in Parasitella. TDH is linked to a gene for a putative acyl-CoA thioesterase (ACT). Two ORFs were identified in the 5'-region of the TDH gene, a third one, coding for 176 amino acids overlaps the ACT gene in antisense direction completely. Expression levels of ACT and ORF1 depend on parasitic and sexual interactions.

Intraspecific variation in two species of Rhizomucor assessed by random amplified polymorphic DNA analysis

Twenty-three Rhizomucor isolates were characterized by random amplified polymorphic DNA-PCR (RAPD-PCR) with 10-bp oligonucleotide primers. These data were used for numerical analyses to obtain information on the intraspecific genetic polymorphism of Rhizomucor species. The genetic variability in Rhizomucor pusillus and Rhizomucor miehei isolates was found to differ; the latter revealed less intraspecific polymorphism. The different levels of genotypic diversity suggest a correlation with the different forms of mating behaviour of these species. Rhizomucor tauricus displayed amplification patterns similar to those of the investigated R. pusillus strains, reinforcing the assumption that R. tauricus does not represent a separate species. Characteristic RAPD markers allowing PCR-based species identification of Rhizomucor isolates were determined.

The combination of Gilbert/Maxam chemical sequencing and the dideoxynucleotide chain termination approach facilitates the construction of species specific PCR-primers based on diagnostic RAPD bands

The randomly amplified polymorphic DNA technique (RAPD) is a modification of PCR that uses short, arbitrarily generated single primers to amplify genomic DNA. Amplified DNA-fragments are often polymorphic and can be used as individual, population- or species-specific markers. Because the RAPD technique requires a very high degree of reproducibility at the instrumentation level and with regard to buffer conditions, we propose to synthesize highly specific conventional PCR primers, the sequence of which is based on the primary diagnostic RAPD bands. In this communication we present a fast and convenient experimental strategy for converting the non-stringent RAPD conditions with their low annealing temperatures to stringent PCR conditions. Diagnostic RAPD bands were sequenced by a combination of chemical (Gilbert/Maxam) and chain termination (Sanger) techniques. Based on this sequence information, highly specific oligonucleotide primers were synthesized. The value of this approach was demonstrated for the molecular diagnosis of the important rape seed (Brassica napus) pathogen Leptosphaeria maculans.