title: Flow cytometric purification of Colletotrichum higginsianum biotrophic hyphae from Arabidopsis leaves for stage-specific transcriptome analysis.
abstract: Generation of stage-specific cDNA libraries is a powerful approach to identify pathogen genes that are differentially expressed during plant infection. Biotrophic pathogens develop specialized infection structures inside living plant cells, but sampling the transcriptome of these structures is problematic due to the low ratio of fungal to plant RNA, and the lack of efficient methods to isolate them from infected plants. Here we established a method, based on fluorescence-activated cell sorting (FACS), to purify the intracellular biotrophic hyphae of Colletotrichum higginsianum from homogenates of infected Arabidopsis leaves. Specific selection of viable hyphae using a fluorescent vital marker provided intact RNA for cDNA library construction. Pilot-scale sequencing showed that the library was enriched with plant-induced and pathogenicity-related fungal genes, including some encoding small, soluble secreted proteins that represent candidate fungal effectors. The high purity of the hyphae (94%) prevented contamination of the library by sequences derived from host cells or other fungal cell types. RT-PCR confirmed that genes identified in the FACS-purified hyphae were also expressed in planta. The method has wide applicability for isolating the infection structures of other plant pathogens, and will facilitate cell-specific transcriptome analysis via deep sequencing and microarray hybridization, as well as proteomic analyses.
authors.affiliation: Department of Plant-Microbe Interactions, Max-Planck-Institute for Plant Breeding Research, 50829 Köln, Germany.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takahara
authors.forename: Andreas
authors.initials: A
authors.lastname: Dolf
authors.forename: Elmar
authors.initials: E
authors.lastname: Endl
authors.forename: Richard
authors.initials: R
authors.lastname: O'Connell
mesh_terms: D017360:Arabidopsis / Q000382:microbiology*; D020231:Colletotrichum / Q000235:genetics* / Q000302:isolation & purification; D020224:Expressed Sequence Tags; D005434:Flow Cytometry; D005452:Fluoresceins; D005456:Fluorescent Dyes; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D015723:Gene Library; D005800:Genes, Fungal; D054884:Host-Pathogen Interactions; D025301:Hyphae / Q000235:genetics / Q000302:isolation & purification* / Q000648:ultrastructure; D018515:Plant Leaves / Q000382:microbiology; D012331:RNA, Fungal / Q000235:genetics / Q000302:isolation & purification
chemical_list: D005452:Fluoresceins; D005456:Fluorescent Dyes; D012331:RNA, Fungal; C018506:diacetylfluorescein