AY-WB phytoplasma secretes a protein that targets plant cell nuclei

Mol Plant Microbe Interact. 2009 Jan;22(1):18-30. doi: 10.1094/MPMI-22-1-0018.


The fully sequenced genome of aster yellows phytoplasma strain witches' broom (AY-WB; Candidatus Phytoplasma asteris) was mined for the presence of genes encoding secreted proteins based on the presence of N-terminal signal peptides (SP). We identified 56 secreted AY-WB proteins (SAP). These SAP are candidate effector proteins potentially involved in interaction with plant and insect cell components. One of these SAP, SAP11, contains an N-terminal SP sequence and a eukaryotic bipartite nuclear localization signal (NLS). Transcripts for SAP11 were detected in AY-WB-infected plants. Yellow fluorescence protein (YFP)-tagged SAP11 accumulated in Nicotiana benthamiana cell nuclei, whereas the nuclear targeting of YFP-tagged SAP11 mutants with disrupted NLS was inhibited. The nuclear transport of YFP-SAP11 was also inhibited in N. benthamiana plants in which the expression of importin alpha was knocked down using virus-induced gene silencing (VIGS). Furthermore, SAP11 was detected by immunocytology in nuclei of young sink tissues of China aster plants infected with AY-WB. In summary, this work shows that AY-WB phytoplasma produces a protein that targets the nuclei of plant host cells; this protein is a potential phytoplasma effector that may alter plant cell physiology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Aster Plant / metabolism
  • Aster Plant / microbiology*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Blotting, Western
  • Cell Nucleus / metabolism*
  • Genome, Bacterial / genetics
  • Molecular Sequence Data
  • Phytoplasma / metabolism*
  • Plants / metabolism
  • Plants / microbiology*


  • Bacterial Proteins