Requirement of LaeA, VeA, and VelB on Asexual Development, Ochratoxin A Biosynthesis, and Fungal Virulence in Aspergillus ochraceus

Abstract

Aspergillus ochraceus is reported to be the major contributor of ochratoxin A (OTA), classified as one of the possible human carcinogen (group 2B) by the International Agency for Research on Cancer. The heterotrimeric velvet complex proteins, LaeA/VeA/VelB, have been most studied in fungi to clarify the relation between light-dependent morphology and secondary metabolism. To explore possible genetic targets to control OTA contamination, we have identified laeA, veA, and velB in A. ochraceus. The loss of laeA, veA, and velB yielded mutants with differences in vegetative growth and conidial production. Especially, ΔlaeA almost lost the ability to generate conidiaphore under dark condition. The deletion of laeA, veA, and velB drastically reduced the production of OTA. The wild-type A. ochraceus produced about 1 and 7 μg/cm2 OTA under light and dark conditions on media, whereas the three gene deletion mutants produced less than 20 ng/cm2 OTA, which was correlated with a down regulation of OTA biosynthetic genes. Pathogenicity studies of ΔlaeA, ΔveA, and ΔvelB showed their reduction in disease severity in pears. Furthermore, 66.1% of the backbone genes in secondary metabolite gene cluster were significantly regulated, among which 81.6% were downregulated. Taking together, these results revealed that velvet complex proteins played crucial roles in asexual development, secondary metabolism, and fungal virulence in A. ochraceus.

Antioxidant‐related catalase CTA1 regulates development, aflatoxin biosynthesis, and virulence in pathogenic fungus Aspergillus flavus

“…It is an adaptation to the stress environment, where CTA1 protects the normal development of A. flavus. In other pathogenic fungi (Olson et al, 2017;Tan et al, 2018;Wang et al, 2019a;Wang et al, 2019b), the deletion of msnA (an orthologue of MsnA2) or veA genes lead to the overexpression of CTA1, which enhances the sexual development. We also found the increased expression of the sexual development-related genes sclR, nsdC and nsdD, in the ΔCTA1 mutant.…”

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

“…In 1993, OTA was listed as a possible carcinogenic substance (group 2B) by the International Agency for Research on Cancer [7]. 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].…”

LaeA Controls Virulence and Secondary Metabolism in Apple Canker Pathogen Valsa mali

“…With the identification of LaeA in plenty of pathogenic fungi, LaeA was regarded as a general virulence factor. Deletion of LaeA weakened the infection ability of A. ochraceus on pear (Wang et al, 2019). In maize pathogen C. heterostrophus, both T-toxin-mediated super virulence and basic pathogenic ability were affected when ChLae1 was deleted or overexpressed (Wu et al, 2012).…”