pH-Signaling Transcription Factor AopacC Regulates Ochratoxin A Biosynthesis in Aspergillus ochraceus

Abstract

In Aspergillus and Penicillium species, an essential pH-response transcription factor pacC is involved in growth, pathogenicity, and toxigenicity. To investigate the connection between ochratoxin A (OTA) biosynthesis and ambient pH, the AopacC in Aspergillus ochraceus was functionally characterized using a loss-of-function mutant. The mycelium growth was inhibited under pH 4.5 and 10.0, while the sporulation increased under alkaline condition. A reduction of mycelium growth and an elevation of sporulation was observed in Δ AopacC mutant. Compared to neutral condition, OTA contents were respectively reduced by 71.6 and 79.8% under acidic and alkaline conditions. The expression of AopacC increased with the elevated pH, and deleting AopacC dramatically decreased OTA production and biosynthetic genes Aopks expression. Additionally, the Δ AopacC mutant exhibited attenuated infection ability toward pear fruits. These results suggest that AopacC is an alkaline-induced regulator responsible for growth and OTA biosynthesis in A. ochraceus and this regulatory mechanism might be pH-dependent.

The pH-Responsive Transcription Factor PacC Governs Pathogenicity and Ochratoxin A Biosynthesis in Aspergillus carbonarius

“…It has been already reported that OTA biosynthesis is regulated by PacC in Aspergillus ochraceus (Wang et al, 2018). Although the growth of the AopacC mutant and its ability to produce OTA were compromised to some degree, an increase in conidia formation has been observed compared to that of the wild type strain, suggesting that PacC in A. ochraceus positively regulates growth and OTA biosynthesis, but has a negative regulatory role in sporulation.…”

“…AcpacC strain, an increase in conidia formation was observed in A. ochraceus pacC mutant compared to that of the WT strain under all the pH conditions (Wang et al, 2018). Therefore, it is likely that PacC plays different roles in mycelial growth and sporulation of different fungal pathogens.…”

“…On the contrary, PacC negatively regulates fumonisin biosynthesis in F. verticillioides and trichothecene biosynthesis in F. graminearum (Flaherty et al, 2003;Merhej et al, 2011). In A. ochraceus, another OTA producing pathogen, PacC played a positive role in regulating OTA biosynthesis, which was slightly impaired in AopacC loss-of-function mutant (Wang et al, 2018). Thus, PacC appears to function differently in regulating secondary metabolites in different fungal pathogens; yet, many unanswered questions remain on the mechanism of this regulation.…”

“…PacC has been previously shown to differentially regulate virulence as well as biosynthesis and secretion of secondary metabolites in several fungal species. Decreased fungal virulence as well as reduction in biosynthesis of secondary metabolites, as a result of pacC knockout, have been observed in several Aspergillus and Penicillium species (Suarez and Penalva, 1996;Keller et al, 1997;Bergh and Brakhage, 1998;Zhang et al, 2013;Chen et al, 2018;Wang et al, 2018). In contrast, disruption of pacC resulted in increased pathogenicity of Fusarium oxysporum (Caracuel et al, 2003) and higher trichothecene and fumonisin production in F. graminearum and Fusarium verticillioides, respectively, compared to the wild type strains (Flaherty et al, 2003;Merhej et al, 2011), suggesting that this transcription factor acts as a negative regulator of virulence and secondary metabolism in Fusarium spp.…”

Estudos estruturais e funcionais de uma lipase de Beauveria bassiana imobilizada e expressa em Aspergillus nidulans: sensibilidade de linhagens celulares de glioblastoma aos hidrolisados de óleos brasileiros

“…De fato, quanto à A. nidulans, são as enzimas xilanolíticas e celulolíticas as menos expressas na presença de glicose(RIES et al, 2016), podendo haver especificidades e funcionalidades distintas entre as duas espécies. no perfil de expressão de genes relacionados com enzimas amilolíticas no gênero Aspergillus(YIN et al, 2017;WANG et al, 2018), podendo haver uma relação com os resultados observados. O tampão fosfato pôde não apenas atuar na regulação de pH, mas também fornecer íons e cofatores para enzimas importantes de seu metabolismo celular, o que justificaria o aumento na produção de proteínas extracelulares, Bbl1 e crescimento em biomassa.Ambas agitação e aeração são importantes em todos os processos aeróbicos; aumento no balanço ATP/ADP, NAD + /NADH, glicólise, fosforilação oxidativa, metabolismo de proteínas e, pela homogeneização do meio, garantindo acesso igual aos nutrientes e oxigênio dissolvidos no meio(ZHOU et al, 2018).…”