Interpretation of mtDNA RFLP variability among Aspergillus tubingensis isolates

Abstract

Aspergillus tubingensis isolates collected from distant geographic areas were earlier classified into six groups on the basis of the mtDNA RFLP variability they exhibited (mtDNA types 2a-2f). In the present work, we investigated the reason for the intraspecific mtDNA variability and we describe here how this fungus, with a relatively small mitochondrial genome, can display intraspecific polymorphism due to intron acquisition and also sporadic point mutations affecting the recognition motifs of the restriction enzymes employed in the RFLP analysis. Three different LAGLI-DADG type group I introns were identified in the cox1 gene amongst the six mtDNA RFLP types. MtDNAs of types 2b and 2d contain all of the three introns, mtDNA of type 2f carries only one, and the other mtDNA types contain two introns each. Comparative analysis showed that the first and second introns of mtDNAs of types 2b and 2d are well distributed among fungi, indicating their active horizontal transfer capacity. The third intron occurs rarely among fungi and is restricted to a limited number of fungal species, namely to A. tubingensis and the yeast Candida stellata. It is interesting that this intron is present in a small mitochondrial genome such as that of A. tubingensis and, considering its rarity, its presence amongst black Aspergillus isolates is recommended to be considered as a tool to establish taxonomical unit(s) or to track down evolutionary divergence of closely related taxonomical units.

Identification of Aspergillus tubingensis strains responsible for OTA contamination in grapes and wine based on the acyl transferase domain of a polyketide synthase gene

“…Phylogenetic study supports intraspecific variability found within A. tubingensis by other authors (Varga et al. , 1993, 1994; Juhász et al. , 2004, 2007).…”

“…Aspergillus tubingensis species have become a greater focus of attention since its high incidence on grapes and OTA-producing ability were described (Medina et al, 2005;Battilani et al, 2006;Perrone et al, 2006a,b). Furthermore, intraspecific variability has been reported within A. tubingensis species (Varga et al, 1993(Varga et al, , 1994Juha´sz et al, 2004Juha´sz et al, , 2007Martı´nez-Culebras & Ramo´n, 2007). Accurate identification of different A. tubingensis isolates might be important to determining toxicological risks because the toxic profile of each isolate could differ.…”

Comparative analysis of the complete mitochondrial genomes of Aspergillus niger mtDNA type 1a and Aspergillus tubingensis mtDNA type 2b

“…In fact, interspecific length variability of mtDNAs among filamentous fungi, like Aspergillus nidulans, Podospora anserina, Neurospora crassa and their relatives are based on the altered intron content of genes and the optional presence of free-standing intronic ORFs (Earl et al, 1981;Collins & Lambowitz, 1983;Koll et al, 1996;Belcour et al, 1997). The same is the reason for the intraspecific mtDNA polymorphism, which seems to be a very typical feature of the imperfect black Aspergilli, like Aspergillus carbonarius (Kevei et al, 1996;Hamari et al, 1999), Aspergillus japonicus , A. niger (Hamari et al, 2003) and A. tubingensis (Juhász et al, 2007). Mitochondrial introns are considered as mobile elements due to their 'parasitic' ORFs, which provide the introns with mobile characteristics (Lambowitz & Belfort, 1993).…”

Characterization of Aspergillus species on Brazil nut from the Brazilian Amazonian region and development of a PCR assay for identification at the genus level

“…The mitochondrial genome is an attractive molecule for application in fungal taxonomy and systematics, with a rapid rate of evolution and limited genetic recombination [38,39]. For Aspergillus , both specific and intraspecific level comparisons have been described [40,41]. Considering the high copy number per cell, mitochondrial DNA (mtDNA) is also easily amplifiable by PCR and appropriate for characterization through RFLP analysis.…”