title: Molecular diagnostic tools for detection and differentiation of phytoplasmas based on chaperonin-60 reveal differences in host plant infection patterns.
abstract: Phytoplasmas ('Candidatus Phytoplasma' spp.) are insect-vectored bacteria that infect a wide variety of plants, including many agriculturally important species. The infections can cause devastating yield losses by inducing morphological changes that dramatically alter inflorescence development. Detection of phytoplasma infection typically utilizes sequences located within the 16S-23S rRNA-encoding locus, and these sequences are necessary for strain identification by currently accepted standards for phytoplasma classification. However, these methods can generate PCR products >1400 bp that are less divergent in sequence than protein-encoding genes, limiting strain resolution in certain cases. We describe a method for accessing the chaperonin-60 (cpn60) gene sequence from a diverse array of 'Ca.Phytoplasma' spp. Two degenerate primer sets were designed based on the known sequence diversity of cpn60 from 'Ca.Phytoplasma' spp. and used to amplify cpn60 gene fragments from various reference samples and infected plant tissues. Forty three cpn60 sequences were thereby determined. The cpn60 PCR-gel electrophoresis method was highly sensitive compared to 16S-23S-targeted PCR-gel electrophoresis. The topology of a phylogenetic tree generated using cpn60 sequences was congruent with that reported for 16S rRNA-encoding genes. The cpn60 sequences were used to design a hybridization array using oligonucleotide-coupled fluorescent microspheres, providing rapid diagnosis and typing of phytoplasma infections. The oligonucleotide-coupled fluorescent microsphere assay revealed samples that were infected simultaneously with two subtypes of phytoplasma. These tools were applied to show that two host plants, Brassica napus and Camelina sativa, displayed different phytoplasma infection patterns.
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon Research Centre, Saskatoon, Saskatchewan, Canada; Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Dumonceaux
authors.affiliation: Canadian Food Inspection Agency, Centre for Plant Health, Sidney, British Columbia, Canada.
authors.forename: Margaret
authors.initials: M
authors.lastname: Green
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon Research Centre, Saskatoon, Saskatchewan, Canada.
authors.forename: Christine
authors.initials: C
authors.lastname: Hammond
authors.affiliation: Instituto de Biotecnologia y Ecologia Aplicada (INBIOTECA), Universidad Veracruzana, Avenida de Las Culturas Veracruzanas, Xalapa, Veracruz, Mexico.
authors.forename: Edel
authors.initials: E
authors.lastname: Perez
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon Research Centre, Saskatoon, Saskatchewan, Canada.
authors.forename: Chrystel
authors.initials: C
authors.lastname: Olivier
mesh_terms: D001483:Base Sequence; D029688:Brassica napus / Q000382:microbiology*; D028244:Camellia / Q000382:microbiology*; D018834:Chaperonin 60 / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D005453:Fluorescence; D008863:Microspheres; D008969:Molecular Sequence Data; D057089:Pathology, Molecular / Q000379:methods; D010802:Phylogeny; D045582:Phytoplasma / Q000145:classification / Q000235:genetics*; D010935:Plant Diseases / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D018834:Chaperonin 60; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S