title: A few sequence polymorphisms among isolates of Maize bushy stunt phytoplasma associate with organ proliferation symptoms of infected maize plants.
abstract: Maize bushy stunt phytoplasma (MBSP) is a bacterial pathogen of maize ( Zea mays L.) across Latin America. MBSP belongs to the 16SrI-B sub-group within the genus ' Candidatus Phytoplasma'. MBSP and its insect vector Dalbulus maidis (Hemiptera: Cicadellidae) are restricted to maize; both are thought to have coevolved with maize during its domestication from a teosinte-like ancestor. MBSP-infected maize plants show a diversity of symptoms. and it is likely that MBSP is under strong selection for increased virulence and insect transmission on maize hybrids that are widely grown in Brazil. In this study it was investigated whether the differences in genome sequences of MBSP isolates from two maize-growing regions in South-east Brazil explain variations in symptom severity of the MBSP isolates on various maize genotypes.
  
  
  
  MBSP isolates were collected from maize production fields in Guaíra and Piracicaba in South-east Brazil for infection assays. One representative isolate was chosen for de novo whole-genome assembly and for the alignment of sequence reads from the genomes of other phytoplasma isolates to detect polymorphisms. Statistical methods were applied to investigate the correlation between variations in disease symptoms of infected maize plants and MBSP sequence polymorphisms.
  
  
  
  MBSP isolates contributed consistently to organ proliferation symptoms and maize genotype to leaf necrosis, reddening and yellowing of infected maize plants. The symptom differences are associated with polymorphisms in a phase-variable lipoprotein, which is a candidate effector, and an ATP-dependent lipoprotein ABC export protein, whereas no polymorphisms were observed in other candidate effector genes. Lipoproteins and ABC export proteins activate host defence responses, regulate pathogen attachment to host cells and activate effector secretion systems in other pathogens.
  
  
  
  Polymorphisms in two putative virulence genes among MBSP isolates from maize-growing regions in South-east Brazil are associated with variations in organ proliferation symptoms of MBSP-infected maize plants.
authors.affiliation: John Innes Centre, Department of Cell and Developmental Biology, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Zigmunds
authors.initials: Z
authors.lastname: Orlovskis
authors.affiliation: John Innes Centre, Department of Cell and Developmental Biology, Norwich Research Park, Norwich NR4 7UH, UK.|Luiz de Queiroz College of Agriculture, University of São Paulo, Department of Entomology and Acarology, Piracicaba 13·418-900, Brazil.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Canale
authors.affiliation: Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Mindia
authors.initials: M
authors.lastname: Haryono
authors.affiliation: Luiz de Queiroz College of Agriculture, University of São Paulo, Department of Entomology and Acarology, Piracicaba 13·418-900, Brazil.
authors.forename: João Roberto Spotti
authors.initials: JRS
authors.lastname: Lopes
authors.affiliation: Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Chih-Horng
authors.initials: CH
authors.lastname: Kuo
authors.affiliation: John Innes Centre, Department of Cell and Developmental Biology, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Saskia A
authors.initials: SA
authors.lastname: Hogenhout
mesh_terms: D001938:Brazil; D016680:Genome, Bacterial; D045582:Phytoplasma / Q000235:genetics / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology*; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D003313:Zea mays / Q000382:microbiology*
keywords: Obligate biothroph; effector biology; genome-wide association study; plant defence; plant–microbe interactions; vector-borne plant pathogens; virulence genes