Carbon Catabolite Repression Gene AoCreA Regulates Morphological Development and Ochratoxin A Biosynthesis Responding to Carbon Sources in Aspergillus ochraceus.

Gang Wang,Bolei Yang,Chenxi Zhang,Yang Liu,Haiyong Zhang,Yulong Wang,Fuguo Xing

doi:10.3390/toxins12110697

Abstract

Carbon is one of the most important nutrients for the development and secondary metabolism in fungi. CreA is the major transcriptional factor mediating carbon catabolite repression, which is employed in the utilization of carbon sources. Aspergillus ochraceus contaminates various food and feed containing different carbon sources by producing ochratoxin A (OTA). However, little is known about the function of AoCreA in regulating the morphology and OTA production of A. ochraceus. To give an insight into the mechanism of the carbon sources regulating development of A. ochraceus and OTA production, we have identified AoCreA in A. ochraceus. The homologous recombination strategy was used to generate the AoCreA deletion mutant (ΔAoCreA). We have investigated the morphology and OTA production of the wild type (WT) and ΔAoCreA of A. ochraceus with media containing different carbon sources (glucose, fructose, maltose, D-xylose, D-mannose, acetate, D-galactose, D-mannitol and lactose). ΔAoCreA showed a significant growth and conidiation defect on all media as compared with WT. Glucose and maltose were the most inducing media for OTA production by A. ochraceus, followed by sucrose and the nutrient-rich Yeast Extract Sucrose (YES) and Potato Dextrose Agar (PDA). The deletion of AoCreA led to a drastic reduction of OTA production on all kinds of media except PDA, which was supported by the expression profile of OTA biosynthetic genes. Furthermore, infection studies of ΔAoCreA on oats and pears showed the involvement of AoCreA in the pathogenicity of A. ochraceus. Thus, these results suggest that AoCreA regulates morphological development and OTA biosynthesis in response to carbon sources in A. ochraceus.

Highlights

Ochratoxin A (OTA) is a secondary metabolite produced by different filamentous fungi belonging to the Aspergillus and Penicillium genera, and A. ochraceus is one of the main producer species [1]
The results showed that glucose, sucrose and maltose contribute more to the biosynthesis of ochratoxin A (OTA)
In other carbon sources, little or no OTA was detected (Figure 5A). These results demonstrated that glucose and maltose were more suitable for A. ochraceus to produce OTA, followed by sucrose and the nutrient-rich Yeast Extract Sucrose (YES) and Potato Dextrose Agar (PDA)

Summary

Introduction

Ochratoxin A (OTA) is a secondary metabolite produced by different filamentous fungi belonging to the Aspergillus and Penicillium genera, and A. ochraceus is one of the main producer species [1]. Several metabolites in the ochratoxin family were identified including OTA, OTB, OTC, OTα and OTβ [4,5,6], of which OTA has been shown to be the most toxic, and for this reason, it is widely studied. In 1993, OTA was listed as a possible carcinogenic substance (group 2B) by the International. Based on a comprehensive understanding of the dangers of OTA, researchers have paid more attention to the biosynthetic and regulatory mechanism of the toxin in the producer species [8,9,10,11,12,13]

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Conclusion