title: AY-WB phytoplasma secretes a protein that targets plant cell nuclei.
abstract: 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.
authors.affiliation: Department of Entomology, The Ohio State University-OARDC, Wooster 44691, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Bai
authors.forename: Valdir R
authors.initials: VR
authors.lastname: Correa
authors.forename: Tania Y
authors.initials: TY
authors.lastname: Toruño
authors.forename: El-Desouky
authors.initials: el-D
authors.lastname: Ammar
authors.forename: Sophien
authors.initials: S
authors.lastname: Kamoun
authors.forename: Saskia A
authors.initials: SA
authors.lastname: Hogenhout
mesh_terms: D000595:Amino Acid Sequence; D031173:Aster Plant / Q000378:metabolism / Q000382:microbiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism*; D016680:Genome, Bacterial / Q000235:genetics; D008969:Molecular Sequence Data; D045582:Phytoplasma / Q000378:metabolism*; D010944:Plants / Q000378:metabolism / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins