Abstract
Various signaling pathways in filamentous fungi help cells receive and respond to environmental information. Previous studies have shown that the mitogen-activated protein kinase (MAPK) pathway is phosphorylation-dependent and activated by different kinase proteins. Serine/threonine kinase plays a very important role in the MAPK pathway. In this study, we selected the serine/threonine kinase AflSte20 in Aspergillus flavus for functional study. By constructing Aflste20 knockout mutants and complemented strains, it was proven that the Aflste20 knockout mutant (ΔAflste20) showed a significant decrease in growth, sporogenesis, sclerotinogenesis, virulence, and infection compared to the WT (wild type) and complemented strain (ΔAflste20C). Further research indicated that ΔAflste20 has more sensitivity characteristics than WT and ΔAflste20C under various stimuli such as osmotic stress and other types of environmental stresses. Above all, our study showed that the mitogen-activated kinase AflSte20 plays an important role in the growth, conidia production, stress response and sclerotia formation, as well as aflatoxin biosynthesis, in A. flavus.
Highlights
Aspergillus flavus is a common saprophytic aerobic fungus
Previous studies found that the mitogen-activated protein kinase (MAPK) pathway plays an important role in eukaryotes, and that the cascade of MAPK is involved in apoptosis, growth regulation, hyperosmosis regulation, cell tolerance, gene expression, cell division, and ascospore development [11]
The activated Ste20 can bind with the SH3 domain of Sho1 to promote the activation of Hog1 [29], and it participates in the mycelium growth, colony reproduction, and other life activities [27]
Summary
Aspergillus flavus is a common saprophytic aerobic fungus. It belongs to the family of Aspergillaceae in the phylum of Ascomycota and is mainly distributed in the warm temperate zone [1]. Transportation, and storage of crops, A. flavus can induce various crop diseases like ear rot in corn, aflaroot in peanuts, and boll rot in cotton [5]. Food safety issues caused by A. flavus are due to its representative secondary metabolites: aflatoxins (AFT), cyclopiazonic acid (CPA), and aflatrem, et al [1,6,7,8]. As a highly toxic fungal toxin with very stable physical and chemical properties, was classified as a first-grade carcinogen by the World Health Organization’s (WHO) international agency for research on cancer in 1993 [9]
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