Evidence of the Involvement of a Cyclase Gene in the Biosynthesis of Ochratoxin A in Aspergillus carbonarius

Abstract

Ochratoxin A (OTA) is a well-known mycotoxin with wide distribution in food and feed. Fungal genome sequencing has great utility for identifying secondary metabolites gene clusters for known and novel compounds. A comparative analysis of the OTA-biosynthetic cluster in A. steynii, A. westerdijkiae, A. niger, A. carbonarius, and P. nordicum has revealed a high synteny in OTA cluster organization in five structural genes (otaA, otaB, ota, otaR1, and otaD). Moreover, a recent detailed comparative genome analysis of Aspergilli OTA producers led to the identification of a cyclase gene, otaY, located in the OTA cluster between the otaA and otaB genes, encoding for a predicted protein with high similarity to SnoaLs domain. These proteins have been shown to catalyze ring closure steps in the biosynthesis of polyketide antibiotics produced in Streptomyces. In the present study, we demonstrated an upregulation of the cyclase gene in A. carbonarius under OTA permissive conditions, consistent with the expression trends of the other OTA cluster genes and their role in OTA biosynthesis by complete gene deletion. Our results pointed out the involvement of a cyclase gene in OTA biosynthetic pathway for the first time. They represent a step forward in the understanding of the molecular basis of OTA biosynthesis in A. carbonarius.

Postharvest Rot of Pomegranate Fruit in Southern Italy: Characterization of the Main Pathogens

“…The presence of these fungi on pomegranate is relevant from a sanitary point of view, since A. welwitschiae strains are potential producers of the mycotoxins fumonisins and ochratoxins [ 19 , 76 ]. Tested isolates proved to be positive for the presence of genes fum8 and fum15 of the fumonisin pathway, but negative for genes involved in OTA biosynthesis [ 26 ], although Ferrara et al [ 77 , 78 ] confirmed the presence of this biosynthetic pathway in A. welwitschiae . Some of the strains were tested by HPLC [ 26 ] to evaluate the amount of these mycotoxins, showing concentrations of FB over the admitted threshold (CE 1126/07) for other plant products.…”

CRISPR/Cas9-Based Genome Editing and Its Application in Aspergillus Species

“…Surprisingly, the identified protein kinases were found to be necessary for both hyphal septation and A. fumigatus ’s capacity to invade lung tissue. In addition to these industrially important strains and pathogenic strains, this versatile genetic manipulation tool has also been successfully established and applied to other Aspergillus species, including A. carbonarius , A. novofumigatus , and A. terreus , among others [ 99 , 100 , 101 , 102 ]. More studies on the development and utilization of the CRISPR/Cas9 genome editing technology in Aspergillus are summarized in Table 1 .…”

The Secondary Metabolites and Biosynthetic Diversity From Aspergillus ochraceus

“…Recently, a cyclase gene otaY was proved to be involved in the biosynthesis of ( 1 ) ( Figure 2 ). OtaY was speculated to catalyze the cyclization process of 7-methylmellein ( Ferrara et al, 2020 ; Ferrara et al, 2021 ).…”