Modulation of fungal virulence through CRZ1 regulated F-BAR-dependent actin remodeling and endocytosis in chickpea infecting phytopathogen Ascochyta rabiei

PLoS Genet. 2021 May 17;17(5):e1009137. doi: 10.1371/journal.pgen.1009137. eCollection 2021 May.

Abstract

Polarized hyphal growth of filamentous pathogenic fungi is an essential event for host penetration and colonization. The long-range early endosomal trafficking during hyphal growth is crucial for nutrient uptake, sensing of host-specific cues, and regulation of effector production. Bin1/Amphiphysin/Rvs167 (BAR) domain-containing proteins mediate fundamental cellular processes, including membrane remodeling and endocytosis. Here, we identified a F-BAR domain protein (ArF-BAR) in the necrotrophic fungus Ascochyta rabiei and demonstrate its involvement in endosome-dependent fungal virulence on the host plant Cicer arietinum. We show that ArF-BAR regulates endocytosis at the hyphal tip, localizes to the early endosomes, and is involved in actin dynamics. Functional studies involving gene knockout and complementation experiments reveal that ArF-BAR is necessary for virulence. The loss-of-function of ArF-BAR gene results in delayed formation of apical septum in fungal cells near growing hyphal tip that is crucial for host penetration, and impaired secretion of a candidate effector having secretory signal peptide for translocation across the endoplasmic reticulum membrane. The mRNA transcripts of ArF-BAR were induced in response to oxidative stress and infection. We also show that ArF-BAR is able to tubulate synthetic liposomes, suggesting the functional role of F-BAR domain in membrane tubule formation in vivo. Further, our studies identified a stress-induced transcription factor, ArCRZ1 (Calcineurin-responsive zinc finger 1), as key transcriptional regulator of ArF-BAR expression. We propose a model in which ArCRZ1 functions upstream of ArF-BAR to regulate A. rabiei virulence through a mechanism that involves endocytosis, effector secretion, and actin cytoskeleton regulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Ascomycota / cytology*
  • Ascomycota / genetics
  • Ascomycota / metabolism
  • Ascomycota / pathogenicity*
  • Cell Nucleus / metabolism
  • Cicer / microbiology*
  • Cytoskeleton / metabolism
  • Endocytosis* / genetics
  • Endosomes / metabolism
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression Regulation, Fungal
  • Liposomes / metabolism
  • Mutation
  • Oxidative Stress
  • Plant Diseases / microbiology
  • Promoter Regions, Genetic / genetics
  • Virulence / genetics

Substances

  • Actins
  • Fungal Proteins
  • Liposomes

Supplementary concepts

  • Ascochyta rabiei

Grants and funding

This research received funding from the Core Grant of National Institute of Plant Genome research to PKV., Department of Biotechnology, Government of India, Grant number: BT/PR10605/PBD/16/791/2008 to PKV, Department of Biotechnology, Government of India, Grant number: BT/AGR/CG-Phase II/01/2014 to PKV and Council of Scientific and Industrial Research, Government of India, Grant number: 19/06/2016(i) EU-V to AS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.