Abstract
Reversible protein phosphorylation is known to play important roles in the regulation of various cellular processes in eukaryotes. Phosphatase-mediated dephosphorylation are integral components of cellular signal pathways by counteracting the phosphorylation action of kinases. In this study, we characterized the functions of CDC14, a dual-specificity phosphatase in the development, secondary metabolism and crop infection of Aspergillus flavus. Deletion of AflCDC14 resulted in a growth defect and abnormal conidium morphology. Inactivation of AflCDC14 caused defective septum and failure to generate sclerotia. Additionally, the AflCDC14 deletion mutant (ΔCDC14) displayed increased sensitivity to osmotic and cell wall integrity stresses. Importantly, it had a significant increase in aflatoxin production, which was consistent with the up-regulation of the expression levels of aflatoxin biosynthesis related genes in ΔCDC14 mutant. Furthermore, seeds infection assays suggested that AflCDC14 was crucial for virulence of A. flavus. It was also found that the activity of amylase was decreased in ΔCDC14 mutant. AflCDC14-eRFP mainly localized to the cytoplasm and vesicles during coidial germination and mycelial development stages. Taken together, these results not only reveal the importance of the CDC14 phosphatase in the regulation of development, aflatoxin biosynthesis and virulence in A. flavus, but may also provide a potential target for controlling crop infections of this fungal pathogen.
Highlights
Aspergillus flavus is a saprophytic and pathogenic fungus which contaminates a variety of economical crops with mycotoxins, causing huge economic losses (Amaike and Keller, 2011; Bhatnagar-Mathur et al, 2015; Lim et al, 2015)
Our results suggest that AflCDC14 may play an important role in asexual development, sclerotial formation, pathogenicity, stress response and secondary metabolism in A. flavus, and may be used as a potential target for curbing the threats posed by A. flavus
CDC14 protein sequences from various fungi, such as Aspergillus spp, N. crassa, M. oryzae, C. albicans, F. graminearum, and S. cerevisiae were downloaded from the NCBI database, and phylogenetic analysis was performed using the downloaded sequences (Figure 1A)
Summary
Aspergillus flavus is a saprophytic and pathogenic fungus which contaminates a variety of economical crops (such as peanuts and maize) with mycotoxins, causing huge economic losses (Amaike and Keller, 2011; Bhatnagar-Mathur et al, 2015; Lim et al, 2015). In human pathogen C. albicans (Wilson and Hube, 2010) and corn smut fungus U. maydis (Pérezmartín et al, 2006), it has been suggested that CDKsare required for cell cycle progression in morphology and virulence. These findings indicate that proper phosphorylation in cell cycle process may be crucial for the development and pathogenicity of filamentous fungi. In contrast to the numerous studies of kinases in different fungi, there have been only few studies of phosphatase regulating cell cycle in filamentous fungi
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