Ras subfamily GTPases regulate development, aflatoxin biosynthesis and pathogenicity in the fungus Aspergillus flavus

Abstract

Ras subfamily proteins are molecular switches in signal transduction pathways of many eukaryotes that regulate a variety of cellular processes. Here, the Ras subfamily, encoded by six genes, was identified in Aspergillus flavus: rasA, rasB, rasC, rab-33, rheb and rsr1. The rsr1 deletion mutant (Δrsr1), rheb deletion mutant (Δrheb) and double deletion mutant (Δrheb/ rsr1) displayed significantly decreased growth and sporulation. Sclerotia formation was significantly decreased for Δrheb or Δrheb/rsr1 but increased for Δrsr1. Aflatoxin production was significantly increased in Δrheb but decreased in Δrsr1 and Δrheb/rsr1. We found that rsr1 and rheb are crucial for the pathogenicity of A. flavus. Quantitative proteomics identified 520 differentially expressed proteins (DEPs) for the Δrsr1 mutant and 133 DEPs for the Δrheb mutant. These DEPs were annotated in multiple biological processes and KEGG pathways in A. flavus. Importantly, we identified the cytokinesis protein SepA in the protein-protein interaction network of rsr1, and deletion mutants showed that SepA has pleiotropic effects on growth and AF biosynthesis, which may depend on Rsr1 for regulation in A. flavus. Our results indicated that these Ras subfamily proteins exhibited functional redundancy with each other but there were also differences in A. flavus.

Palmitoyl Transferase FonPAT2-Catalyzed Palmitoylation of the FonAP-2 Complex Is Essential for Growth, Development, Stress Response, and Virulence in Fusarium oxysporum f. sp. niveum

“…The ABE/LC-MS assay identified a total of 211 putative palmitoylated proteins that were present in the WT but absent in ΔFonpat2 in 2 independent biological replicates, and 36 palmitoylated proteins overlapped in the two replicates (Table S1). Some of the putative palmitoylated proteins were previously reported to be involved in the pathogenicity of filamentous fungi such as F. graminearum , Botrytis cinerea , Verticillium dahliae , and Aspergillus flavus , for example, FOXG_00780 (AP-2 complex subunit α) and FOXG_04448 (AP-2 complex subunit μ) ( 41 , 42 ), FOXG_05141 (autophagy-related ATG7) and FOXG_01866 (ATG20) ( 56 – 58 ), FOXG_11305 (myosin-1) ( 59 ), FOXG_19023 (chitin synthase) ( 60 ), FOXG_13911 (Ras-like protein Rab-11B), and FOXG_03575 (Ras-like C3 botulinum toxin substrate 1) ( 61 ), and FOXG_11168 (ankyrin repeat protein NUC-2) ( 62 ). Meanwhile, homologues for some of the putative palmitoylated proteins were previously shown to be palmitoylated in yeast and other organisms, for example, FOXG_08214 (synaptobrevin-like YKT6) ( 63 ), FOXG_04579 (actin γ) ( 33 ), FOXG_13911 (Ras-like protein Rab-11B), FOXG_03575 (Ras-like C3 botulinum toxin substrate 1) ( 64 ), and FOXG_00122 (Ca 2+ transporting ATPase) ( 33 ).…”

Lysine Succinylation of VBS Contributes to Sclerotia Development and Aflatoxin Biosynthesis in Aspergillus flavus

“…For example, A. flavus proteomics profiling showed that laeA regulates AF biosynthesis by influencing extracellular hydrolases and conidial hydrophobin and responding to oxidative stress ( 27 ). Quantitative proteomic analysis of A. flavus revealed that the Ras subfamily GTPases are crucial for AF biosynthesis and pathogenicity ( 28 ). Therefore, proteomics is an effective technique to study the intricate molecular mechanism underlying AF biosynthesis.…”

The Ras small GTPase RSR1 regulates cellulase production in Trichoderma reesei

“…In Ashbya gossypii , rsr1 is involved in hyphal growth guidance [ 51 ]. Moreover, Rsr1 was reported to participate in development regulation, aflatoxin biosynthesis and pathogenicity in Aspergillus flavus [ 52 ]. RSR1 has been widely reported in other fungi, but unfortunately its function in T. reesei remains elusive.…”