title: Variations in type III effector repertoires, pathological phenotypes and host range of Xanthomonas citri pv. citri pathotypes.
abstract: The mechanisms determining the host range of Xanthomonas are still undeciphered, despite much interest in their potential roles in the evolution and emergence of plant pathogenic bacteria. Xanthomonas citri pv. citri (Xci) is an interesting model of host specialization because of its pathogenic variants: pathotype A strains infect a wide range of Rutaceous species, whereas pathotype A*/A(W) strains have a host range restricted to Mexican lime (Citrus aurantifolia) and alemow (Citrus macrophylla). Based on a collection of 55 strains representative of Xci worldwide diversity assessed by amplified fragment length polymorphism (AFLP), we investigated the distribution of type III effectors (T3Es) in relation to host range. We examined the presence of 66 T3Es from xanthomonads in Xci and identified a repertoire of 28 effectors, 26 of which were shared by all Xci strains, whereas two (xopAG and xopC1) were present only in some A*/A(W) strains. We found that xopAG (=avrGf1) was present in all A(W) strains, but also in three A* strains genetically distant from A(W) , and that all xopAG-containing strains induced the hypersensitive response (HR) on grapefruit and sweet orange. The analysis of xopAD and xopAG suggested horizontal transfer between X. citri pv. bilvae, another citrus pathogen, and some Xci strains. A strains were genetically less diverse, induced identical phenotypic responses and possessed indistinguishable T3E repertoires. Conversely, A*/A(W) strains exhibited a wider genetic diversity in which clades correlated with geographical origin and T3E repertoire, but not with pathogenicity, according to T3E deletion experiments. Our data outline the importance of taking into account the heterogeneity of Xci A*/A(W) strains when analysing the mechanisms of host specialization.
authors: UMR PVBMT, CIRAD, F-97410 Saint-Pierre, La Réunion, France.
authors: Aline
authors: A
authors: Escalon
authors: Stéphanie
authors: S
authors: Javegny
authors: Christian
authors: C
authors: Vernière
authors: Laurent D
authors: LD
authors: Noël
authors: Karine
authors: K
authors: Vital
authors: Stéphane
authors: S
authors: Poussier
authors: Ahmed
authors: A
authors: Hajri
authors: Tristan
authors: T
authors: Boureau
authors: Olivier
authors: O
authors: Pruvost
authors: Matthieu
authors: M
authors: Arlat
authors: Lionel
authors: L
authors: Gagnevin
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D001426:Bacterial Proteins / Q000378:metabolism; D058947:Bacterial Secretion Systems / Q000235:genetics*; D016000:Cluster Analysis; D015169:Colony Count, Microbial; D017353:Gene Deletion; D022761:Gene Transfer, Horizontal / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D014644:Genetic Variation; D005843:Geography; D058507:Host Specificity / Q000235:genetics*; D054884:Host-Pathogen Interactions; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D057865:Plant Immunity / Q000235:genetics; D018515:Plant Leaves / Q000382:microbiology; D010944:Plants / Q000382:microbiology; D017422:Sequence Analysis, DNA; D014974:Xanthomonas / Q000145:classification* / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems