AUTHOR=Katayama Takuya , Maruyama Jun-ichi 

TITLE=Trace copper-mediated asexual development via a superoxide dismutase and induction of AobrlA in Aspergillus oryzae

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1135012

DOI=10.3389/fmicb.2023.1135012

ISSN=1664-302X

ABSTRACT=<p>The filamentous fungus <italic>Aspergillus oryzae</italic>, in which sexual reproduction remains to be discovered, proliferates mainly <italic>via</italic> asexual spores (conidia). Therefore, despite its industrial importance in food fermentation and recombinant protein production, breeding beneficial strains by genetic crosses is difficult. In <italic>Aspergillus flavus</italic>, which is genetically close to <italic>A</italic>. <italic>oryzae</italic>, structures known as sclerotia are formed asexually, but they are also related to sexual development. Sclerotia are observed in some <italic>A</italic>. <italic>oryzae</italic> strains, although no sclerotia formation has been reported in most strains. A better understanding of the regulatory mechanisms underlying sclerotia formation in <italic>A</italic>. <italic>oryzae</italic> may contribute to discover its sexual development. Some factors involved in sclerotia formation have been previously identified, but their regulatory mechanisms have not been well studied in <italic>A</italic>. <italic>oryzae</italic>. In this study, we found that copper strongly inhibited sclerotia formation and induced conidiation. Deletion of <italic>AobrlA</italic> encoding a core regulator of conidiation and <italic>ecdR</italic> involved in transcriptional induction of <italic>AobrlA</italic> suppressed the copper-mediated inhibition of sclerotia formation, suggesting that <italic>AobrlA</italic> induction in response to copper leads not only to conidiation but also to inhibition of sclerotia formation. In addition, deletion of the copper-dependent superoxide dismutase (SOD) gene and its copper chaperone gene partially suppressed such copper-mediated induction of conidiation and inhibition of sclerotia formation, indicating that copper regulates asexual development <italic>via</italic> the copper-dependent SOD. Taken together, our results demonstrate that copper regulates asexual development, such as sclerotia formation and conidiation, <italic>via</italic> the copper-dependent SOD and transcriptional induction of <italic>AobrlA</italic> in <italic>A</italic>. <italic>oryzae</italic>.</p>