AUTHOR=Shao Lei , Tan Yumei , Song Shiying , Wang Yuchen , Liu Yongxiang , Huang Yonghui , Ren Xiyi , Liu Zuoyi 

TITLE=Achog1 is required for the asexual sporulation, stress responses and pigmentation of Aspergillus cristatus

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1003244

DOI=10.3389/fmicb.2022.1003244

ISSN=1664-302X

ABSTRACT=<p><italic>Aspergillus cristatus</italic> is the dominant fungus during the fermentation of Fuzhuan brick tea; hypotonic conditions only induce its sexual development to produce ascospores, while hypertonic conditions only induce its asexual development to produce conidia, indicating that osmotic stress can regulate spore production in <italic>A</italic>. <italic>cristatus</italic>. However, the underlying regulatory mechanism is unclear. In this study, the role of <italic>Achog1</italic>, which is homologous to <italic>hog1</italic> from <italic>Saccharomyces cerevisiae</italic>, in sporulation, different kinds of stress responses and pigment production was investigated. Deletion mutants of <italic>Achog1</italic> were obtained by homologous recombination. Phenotypic observations showed that the time required to produce conidia was delayed, and the number of conidia produced was significantly reduced in the deletion mutants of <italic>Achog1</italic> in hypertonic media, indicating that <italic>Achog1</italic> plays a positive role in asexual development. Stress sensitivity tests showed that Δ<italic>Achog1</italic> strains were sensitive to hyperosmolarity, and the order of the sensitivity of Δ<italic>Achog1</italic> to different osmotic regulators was 3 M sucrose &gt;3 M NaCl &gt;3 M sorbitol. Moreover, the deletion mutants were sensitive to high oxidative stress. pH sensitivity tests indicated that <italic>Achog1</italic> inhibited the growth of <italic>A</italic>. <italic>cristatus</italic> under alkaline stress. Additionally, pigmentation was decreased in the <italic>Achog1</italic> deletion mutants compared with the WT. All the above developmental defects were reversed by the reintroduction of the <italic>Achog1</italic> gene in Δ<italic>Achog1</italic>. Pull-down and LC–MS/MS analysis showed that the expression levels of proteins interacting with <italic>Achog1</italic> were significantly different under low and high osmotic stress, and proteins related to conidial development were present only in the cultures treated with hyperosmotic stress. Transcription profiling data showed that <italic>Achog1</italic> suppressed the expression of several genes related to asexual development, osmotic and oxidative stress resistance. On the basis of gene knockout, pull-down mass spectrometry and RNA-seq analyses, a regulatory pathway for <italic>Achog1</italic> was roughly identified in <italic>A</italic>. <italic>cristatus</italic>.</p>