Powdery mildew fungal effector candidates share N-terminal Y/F/WxC-motif

BMC Genomics. 2010 May 20;11:317. doi: 10.1186/1471-2164-11-317.

Abstract

Background: Powdery mildew and rust fungi are widespread, serious pathogens that depend on developing haustoria in the living plant cells. Haustoria are separated from the host cytoplasm by a plant cell-derived extrahaustorial membrane. They secrete effector proteins, some of which are subsequently transferred across this membrane to the plant cell to suppress defense.

Results: In a cDNA library from barley epidermis containing powdery mildew haustoria, two-thirds of the sequenced ESTs were fungal and represented approximately 3,000 genes. Many of the most highly expressed genes encoded small proteins with N-terminal signal peptides. While these proteins are novel and poorly related, they do share a three-amino acid motif, which we named "Y/F/WxC", in the N-terminal of the mature proteins. The first amino acid of this motif is aromatic: tyrosine, phenylalanine or tryptophan, and the last is always cysteine. In total, we identified 107 such proteins, for which the ESTs represent 19% of the fungal clones in our library, suggesting fundamental roles in haustoria function. While overall sequence similarity between the powdery mildew Y/F/WxC-proteins is low, they do have a highly similar exon-intron structure, suggesting they have a common origin. Interestingly, searches of public fungal genome and EST databases revealed that haustoria-producing rust fungi also encode large numbers of novel, short proteins with signal peptides and the Y/F/WxC-motif. No significant numbers of such proteins were identified from genome and EST sequences from either fungi which do not produce haustoria or from haustoria-producing Oomycetes.

Conclusion: In total, we identified 107, 178 and 57 such Y/F/WxC-proteins from the barley powdery mildew, the wheat stem rust and the wheat leaf rust fungi, respectively. All together, our findings suggest the Y/F/WxC-proteins to be a new class of effectors from haustoria-producing pathogenic fungi.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Ascomycota / classification
  • Ascomycota / genetics*
  • Ascomycota / metabolism
  • Conserved Sequence
  • Expressed Sequence Tags
  • Fungal Proteins / chemistry*
  • Fungal Proteins / classification
  • Fungal Proteins / genetics*
  • Fungal Proteins / metabolism
  • Gene Expression Regulation, Fungal
  • Genes, Fungal / genetics
  • Phylogeny
  • Plant Diseases / microbiology*
  • Plant Leaves / physiology
  • Protein Sorting Signals / genetics
  • Triticum / microbiology

Substances

  • Fungal Proteins
  • Protein Sorting Signals