Variation in the fumonisin biosynthetic gene cluster in fumonisin-producing and nonproducing black aspergilli

Abstract

The ability to produce fumonisin mycotoxins varies among members of the black aspergilli. Previously, analyses of selected genes in the fumonisin biosynthetic gene (fum) cluster in black aspergilli from California grapes indicated that fumonisin-nonproducing isolates of Aspergillus welwitschiae lack six fum genes, but nonproducing isolates of Aspergillus niger do not. In the current study, analyses of black aspergilli from grapes from the Mediterranean Basin indicate that the genomic context of the fum cluster is the same in isolates of A. niger and A. welwitschiae regardless of fumonisin-production ability and that full-length clusters occur in producing isolates of both species and nonproducing isolates of A. niger. In contrast, the cluster has undergone an eight-gene deletion in fumonisin-nonproducing isolates of A. welwitschiae. Phylogenetic analyses suggest each species consists of a mixed population of fumonisin-producing and nonproducing individuals, and that existence of both production phenotypes may provide a selective advantage to these species. Differences in gene content of fum cluster homologues and phylogenetic relationships of fum genes suggest that the mutation(s) responsible for the nonproduction phenotype differs, and therefore arose independently, in the two species. Partial fum cluster homologues were also identified in genome sequences of four other black Aspergillus species. Gene content of these partial clusters and phylogenetic relationships of fum sequences indicate that non-random partial deletion of the cluster has occurred multiple times among the species. This in turn suggests that an intact cluster and fumonisin production were once more widespread among black aspergilli.

Isolation, Molecular Identification, and Mycotoxin Production of Aspergillus Species Isolated from the Rhizosphere of Sugarcane in the South of Iran

“…On the contrary, the presence of A. welwitschiae strains that produce both OTA and FB2 is worrisome, since both of these mycotoxins are considered by the International Agency for Cancer Research (IARC) group 2b, meaning potentially carcinogenic. Only a minority of strains analyzed were able to produce only OTA, while the majority of A. welwitschiae strains (80%) also produced FB2, in agreement with previous reports [33,35]. Some authors have demonstrated that OTA production in A. niger is affected by temperature [36], while in A. welwitschiae, it is affected by water activity and the medium [37].…”

“…OTA residue was dissolved with 1 mL of acetonitrile/water/glacial acetic acid (99:99:2, v/v/v) and filtered using RC through a 0.20 µm regenerated cellulose filter and determined by HPLC/FLD. OTA quantification was performed according to Susca et al [35]. The quantification limit (LOQ) was 0.05 µg/g based on a signal to noise ratio of 10:1.…”

Whole-genome sequencing of Aspergillus tubingensis G131 and overview of its secondary metabolism potential

“…Based on the current knowledge about the biosynthesis of these mycotoxins, BLAST analyses were performed to check the mycotoxins production potentiality in A. tubingensis G131 strain, a methodology that was already described for different genomic works on Aspergillus sp. [27,43,44].…”

“…The fumonisin gene cluster of A. niger contains at least 14 fum genes [43]. A previous study showed that A. luchuensis NBRC 4314 genome only contains orthologues for fum1 and fum15 with high identity: 68 and 72%, respectively [27].…”

“…Moreover, others FUM were predicted to be encoded by A. luchuensis, but the proteins only shared 20-43% identities and the orthologue genes of such proteins were distributed throughout the A. luchuensis genome. Susca et al [43] suggested that fumonisin production was widespread among black Aspergilli. They demonstrated that nonrandom partial deletion of fumonisin cluster has occurred multiple times in several black Aspergilli genomes.…”