Browsing by Person "Huettel, Bruno"

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Divergence within the taxon ‘Candidatus Phytoplasma asteris’ confirmed by comparative genome analysis of carrot strains
(2024) Toth, Rafael; Ilic, Anna-Marie; Huettel, Bruno; Duduk, Bojan; Kube, Michael
Phytoplasmas are linked to diseases in hundreds of economically important crops, including carrots. In carrots, phytoplasmosis is associated with leaf chlorosis and necrosis, coupled with inhibited root system development, ultimately leading to significant economic losses. During a field study conducted in Baden-Württemberg (Germany), two strains of the provisional taxon ‘Candidatus Phytoplasma asteris’ were identified within a carrot plot. For further analysis, strains M8 and M33 underwent shotgun sequencing, utilising single-molecule-real-time (SMRT) long-read sequencing and sequencing-by-synthesis (SBS) paired-end short-read sequencing techniques. Hybrid assemblies resulted in complete de novo assemblies of two genomes harboring circular chromosomes and two plasmids. Analyses, including average nucleotide identity and sequence comparisons of established marker genes, confirmed the phylogenetic divergence of ‘Ca. P. asteris’ and a different assignment of strains to the 16S rRNA subgroup I-A for M33 and I-B for M8. These groups exhibited unique features, encompassing virulence factors and genes, associated with the mobilome. In contrast, pan-genome analysis revealed a highly conserved gene set related to metabolism across these strains. This analysis of the Aster Yellows (AY) group reaffirms the perception of phytoplasmas as bacteria that have undergone extensive genome reduction during their co-evolution with the host and an increase of genome size by mobilome.
The 16SrXII-P phytoplasma GOE is separated from other stolbur phytoplasmas by key genomic features
(2025) Toth, Rafael; Huettel, Bruno; Varrelmann, Mark; Kube, Michael; Toth, Rafael; Department of Integrative Infection Biology Crops-Livestock, University of Hohenheim, 70599 Stuttgart, Germany;; Huettel, Bruno; Max Planck-Genome-Center Cologne, 50829 Cologne, Germany;; Varrelmann, Mark; Institute of Sugar Beet Research (IfZ), 37079 Göttingen, Germany;; Kube, Michael; Department of Integrative Infection Biology Crops-Livestock, University of Hohenheim, 70599 Stuttgart, Germany;; Kizheva, Yoana; Hristova, Petya
The syndrome “bassess richesses” is a vector-borne disease of sugar beet in Germany. The gammaproteobacterium ‘ Candidatus Arsenophonus phytopathogenicus’ causes reduced sugar content and biomass, growth abnormalities, and yellowing. Co-infection with the 16SrXII-P stolbur phytoplasmas often leads to more severe symptoms and a risk of complete economic loss. This yellowing agent of the Mollicutes class had not been described before, so its differences from other stolbur phytoplasmas remained unanswered. The genome of strain GOE was sequenced, providing a resource to analyze its characteristics. Phylogenetic position was revised, genome organization was compared, and functional reconstructions of metabolic and virulence factors were performed. Average nucleotide identity analysis indicates that GOE represents a new ‘ Ca. Phytoplasma’ species. Our results show that GOE is also distinct from other stolbur phytoplasmas in terms of smaller genome size and G+C content. Its reductive evolution is reflected in conserved membrane protein repertoire and minimal metabolism. The encoding of a riboflavin kinase indicates a lost pathway of phytoplasmas outside the groups 16SrXII and 16SrXIII. GOE shows a complete tra5 transposon harboring orthologs of SAP11, SAP54, and SAP05 effectors indicating an original phytoplasma pathogenicity island. Our results deepen the understanding of phytoplasma evolution and reaffirm the heterogeneity of stolbur phytoplasmas.