Cation-Stress-Responsive Transcription Factors SltA and CrzA Regulate Morphogenetic Processes and Pathogenicity of Colletotrichum gloeosporioides

PLoS One. 2016 Dec 28;11(12):e0168561. doi: 10.1371/journal.pone.0168561. eCollection 2016.

Abstract

Growth of Colletotrichum gloeosporioides in the presence of cation salts NaCl and KCl inhibited fungal growth and anthracnose symptom of colonization. Previous reports indicate that adaptation of Aspergillus nidulans to salt- and osmotic-stress conditions revealed the role of zinc-finger transcription factors SltA and CrzA in cation homeostasis. Homologs of A. nidulans SltA and CrzA were identified in C. gloeosporioides. The C. gloeosporioides CrzA homolog is a 682-amino acid protein, which contains a C2H2 zinc finger DNA-binding domain that is highly conserved among CrzA proteins from yeast and filamentous fungi. The C. gloeosporioides SltA homolog encodes a 775-amino acid protein with strong similarity to A. nidulans SltA and Trichoderma reesei ACE1, and highest conservation in the three zinc-finger regions with almost no changes compared to ACE1 sequences. Knockout of C. gloeosporioides crzA (ΔcrzA) resulted in a phenotype with inhibited growth, sporulation, germination and appressorium formation, indicating the importance of this calciu006D-activated transcription factor in regulating these morphogenetic processes. In contrast, knockout of C. gloeosporioides sltA (ΔsltA) mainly inhibited appressorium formation. Both mutants had reduced pathogenicity on mango and avocado fruit. Inhibition of the different morphogenetic stages in the ΔcrzA mutant was accompanied by drastic inhibition of chitin synthase A and B and glucan synthase, which was partially restored with Ca2+ supplementation. Inhibition of appressorium formation in ΔsltA mutants was accompanied by downregulation of the MAP kinase pmk1 and carnitine acetyl transferase (cat1), genes involved in appressorium formation and colonization, which was restored by Ca2+ supplementation. Furthermore, exposure of C. gloeosporioides ΔcrzA or ΔsltA mutants to cations such as Na+, K+ and Li+ at concentrations that the wild type C. gloeosporioides is not affected had further adverse morphogenetic effects on C. gloeosporioides which were partially or fully restored by Ca2+. Overall results suggest that both genes modulating alkali cation homeostasis have significant morphogenetic effects that reduce C. gloeosporioides colonization.

MeSH terms

  • Cations, Divalent / toxicity*
  • Colletotrichum / genetics
  • Colletotrichum / growth & development*
  • Colletotrichum / metabolism
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression Regulation, Fungal / drug effects*
  • Morphogenesis / drug effects
  • Morphogenesis / physiology*
  • Persea / microbiology*
  • Phenotype
  • Plant Diseases / genetics
  • Plant Diseases / immunology
  • Plant Diseases / microbiology*
  • Spores, Fungal / physiology
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Virulence / genetics
  • Zinc Fingers

Substances

  • Cations, Divalent
  • Fungal Proteins
  • Transcription Factors

Grants and funding

This work was supported by the US/Israel Binational Agricultural Research Fund (ISBARD), grant no. IS-4773-14, the Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional (FEDER), grant nos. BFU2012-33142 and BFU2015-66806R. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.