Molecular and structural basis of nucleoside diphosphate kinase–mediated regulation of spore and sclerotia development in the fungus Aspergillus flavus

Abstract

The fundamental biological function of nucleoside diphosphate kinase (NDK) is to catalyze the reversible exchange of the ␥-phosphate between nucleoside triphosphate (NTP) and nucleoside diphosphate (NDP). This kinase also has functions that extend beyond its canonically defined enzymatic role as a phosphotransferase. However, the role of NDK in filamentous fungi, especially in Aspergillus flavus (A. flavus), is not yet known. Here we report that A. flavus has two NDK-encoding gene copies as assessed by qPCR. Using gene-knockout and complementation experiments, we found that AfNDK regulates spore and sclerotia development and is involved in plant virulence as assessed in corn and peanut seed-based assays. An antifungal test with the inhibitor azidothymidine suppressed AfNDK activity in vitro and prevented spore production and sclerotia formation in A. flavus, confirming AfNDK's regulatory functions. Crystallographic analysis of AfNDK, coupled with site-directed mutagenesis experiments, revealed three residues (Arg-104, His-117, and Asp-120) as key sites that contribute to spore and sclerotia development. These results not only enrich our knowledge of the regulatory role of this important protein in A. flavus, but also provide insights into the prevention of A. flavus infection in plants and seeds, as well as into the structural features relevant for future antifungal drug development. cro ARTICLE

Magnaporthe oryzae nucleoside diphosphate kinase is required for metabolic homeostasis and redox‐mediated host innate immunity suppression

“…In yeast, the sole NDPK homologue YNK1 (Fukuchi et al ., 1993) is required for maintaining nucleotide pool homeostasis but is not required for cell viability (likely due to the residual synthesis of NTPs by alternative pathways). In filamentous fungi, NDPK homologues in Neurospora crassa (Lee et al ., 2009) and Aspegillus flavus (Wang et al ., 2019) are not required for viability whereas an A. nidulans NDPK, SwoHp, is essential (Lin et al ., 2003). To our knowledge, NDPKs have not been studied in phytopathogenic fungi with specialized infection strategies.…”

MAPK pathway‐related tyrosine phosphatases regulate development, secondary metabolism and pathogenicity in fungus Aspergillus flavus

“…Aspergillus flavus is a saprobic and plant pathogenic fungus that contaminates various economically important crops (such as maize, peanuts and tree nuts) with the carcinogenic aflatoxins (AFs) (Amaike and Keller, 2011). Aspergillus flavus is also an opportunistic pathogen of mammalian hosts and the second-leading cause of aspergillosis after Aspergillus fumigatus (Hedayati et al, 2007;Lan et al, 2019;Wang et al, 2019). AFs, which are the toxic and carcinogenic secondary metabolites of A. flavus, continue to be a major threat to human health and food safety (Fasoyin et al, 2018;Zhu et al, 2020).…”

Exposure of Aspergillus flavus NRRL 3357 to the Environmental Toxin, 2,3,7,8-Tetrachlorinated Dibenzo-p-Dioxin, Results in a Hyper Aflatoxicogenic Phenotype: A Possible Role for Caleosin/Peroxygenase (AfPXG)

“…Furthermore, the fluffy mutants of A. nidulans and A. flavus that have a defective G-protein signaling pathway resulted in an aconidial, aflatoxin-null phenotype (Calvo et al, 2002; Affeldt et al, 2012). More recently, the nucleoside diphosphate kinase (AfNDK), which was newly characterized in A. flavus , regulates spore and sclerotia development and is involved in plant infection (Wang et al, 2019). Additionally, the HosA, a new histone deacetylase recently identified in A. flavus , plays a determinant role in growth, development and AF biosynthesis (Lan et al, 2019).…”