Publications

4378

Phytoplasmas are obligate intracellular pathogens that profoundly modify the development, physiology and behavior of their hosts by secreting effector proteins that disturb signal pathways and interactions both in plant and insect hosts. The characterization of effectors and their host-cell targets was performed for only a few phytoplasma species where it was shown that the SAP11 effector alters plant morphology by destabilizing plant transcription factors: TEOSINTE BRANCHED 1-CYCLOIDEA-PROLIFERATING CELL FACTOR (TCPs). To explore the possible role of the SAP11-like effector from ‘Ca. P. solani’, we used Arabidopsis thaliana as a model plant. The SAP11-like effector gene from ‘Ca. P. solani’ was introduced into arabidopsis by floral dip and transgenic lines were regenerated. In planta bimolecular fluorescence complementation (BIFC) assays in agroinfiltrated Nicotiana benthamiana leaf cells were conducted to detect interactions between SAP11-like and AtTCP2 and AtTCP4 using confocal microscopy. SAP11-like from ‘Ca. P. solani’ induced significant phenotypic changes in arabidopsis, including crinkled leaves with reduced size, lower biomass, more axillary branches, changes in root morphology, and crinkled and smaller siliques. The BIFC assays proved in planta interaction of SAP11-like effector with AtTCP2 and AtTCP4. To our knowledge, this is the first characterization of the interaction between the ‘Ca. P. solani’ effector and plant transcription factors, suggesting a potential mechanism of modulating plant development and induction of characteristic symptoms in ‘Ca. P. solani’-infected plants.

AbstractTwo new species of Dulcicalothrix, D. adhikaryi sp. nov. and D. iyengarii sp. nov., were discovered in India and are characterized and described in accordance with the rules of the International Code of Nomenclature for algae, fungi, and plants (ICN). As a result of phylogenetic analysis, Calothrix elsteri is reassigned to Brunnivagina gen. nov. During comparison with all Dulcicalothrix for which sequence data were available, we observed that the genus has six ribosomal operons in three orthologous types. Each of the three orthologs could be identified based upon indels occurring in the D1–D1′ helix sequence in the ITS rRNA region between the 16S and 23S rRNA genes, and in these three types, there were operons containing ITS rRNA regions with and without tRNA genes. Examination of complete genomes in Dulcicalothrix revealed that, at least in the three strains for which complete genomes are available, there are five ribosomal operons, two with tRNA genes and three with no tRNA genes in the ITS rRNA region. Internal transcribed spacer rRNA regions have been consistently used to differentiate species, both on the basis of secondary structure and percent dissimilarity. Our findings call into question the use of ITS rRNA regions to differentiate species in the absence of efforts to obtain multiple operons of the ITS rRNA region through cloning or targeted PCR amplicons. The ITS rRNA region data for Dulcicalothrix is woefully incomplete, but we provide herein a means for dealing with incomplete data using the polyphasic approach to analyze diverse molecular character sets. Caution is urged in using ITS rRNA data, but a way forward through the complexity is also proposed.

‘Candidatus Phytoplasma brasiliense’ (CPB) is a phytoplasma originally discovered in South America and is known to infect a wide variety of economically important crops. It is most prevalent in Hibiscus spp., where it causes witches broom symptoms, and papaya, where it causes bunchy top. Recently, CPB was documented for the first time in North America in a new host, globe sedge. In this study, two quantitative PCR assays are developed: one using high-resolution melt curve analysis (HRMA) based on the secA gene and the other a TaqMan assay based on the dnaK gene. The secA/HRMA and dnaK/TaqMan assay successfully amplified two of the three isolates of CPB. Both assays were screened against available isolates of 16SrI, 16SrII, and 16SrIV phytoplasmas. The secA/HRMA assay failed to amplify 16SrI and 16SrIV phytoplasmas but successfully amplified 16SrII phytoplasmas. The resulting melting point (Tm) products of CPB and 16SrII phytoplasmas displayed a difference of 0.5°C, easily distinguishing them by melt curves. The dnaK/TaqMan assay failed to amplify all non-CPB phytoplasma isolates in the study. The development of these assays provides a valuable tool that will significantly improve monitoring programs in Florida and will aid in developing a better fundamental understanding of the epidemiology of this phytoplasma.

AbstractGut microbiota dysbiosis has been implicated in rheumatoid arthritis (RA) and influences disease progression. Although molecular and culture‐independent studies revealed RA patients harbored a core microbiome and had characteristic bacterial species, the lack of cultured bacterial strains had limited investigations on their functions. This study aimed to establish an RA‐originated gut microbial biobank (RAGMB) that covers and further to correlates and validates core microbial species on clinically used and diagnostic inflammation and immune indices. We obtained 3200 bacterial isolates from fecal samples of 20 RA patients with seven improved and 11 traditional bacterial cultivation methods. These isolates were phylogenetically identified and selected for RAGMB. The RAGMB harbored 601 bacterial strains that represented 280 species (including 43 novel species) of seven bacterial phyla. The RAGMB covered 93.2% at species level of medium‐ and high‐abundant (relative abundances ≥0.2%) RA gut microbes, and included four rare species of the phylum Synergistota. The RA core gut microbiome was defined and composed of 20 bacterial species. Among these, Mediterraneibacter tenuis and Eubacterium rectale were two species that statistically and significantly correlated with clinically used diagnostic indices such as erythrocyte sedimentation rate (ESR) and IL‐10. Thus, M. tenuis and E. rectale were selected for experimental validation using DSS‐treated and not DSS‐treated mice model. Results demonstrated both M. tenuis and E. rectale exacerbated host inflammatory responses, including shortened colon length and increased spleen weight, decreased IL‐10 and increased IL‐17A levels in plasma. Overall, we established the RAGMB, defined the RA core microbiome, correlated and demonstrated core microbial species effected on host inflammatory and immune responses. This work provides diverse gut microbial resources for future studies on RA etiology and potential new targets for new biomedical practices.

AbstractMetagenomic analysis was conducted to assess the microbial community in the high‐altitude Tamdykul geothermal spring in Tajikistan. This analysis yielded six high‐quality bins from the members of Thermaceae, Aquificaceae, and Halothiobacillaceae, with a 41.2%, 19.7%, and 18.1% share in the total metagenome, respectively. Minor components included Schleiferia thermophila (1.6%) and members of the archaeal taxa Pyrobaculum (1.2%) and Desulfurococcaceae (0.7%). Further analysis of the metagenome‐assembled genome (MAG) from the Desulfurococcaceae family (MAG002) revealed novel taxonomy with only 80.95% closest placement average nucleotide identity value to its most closely related member of the Desulfurococcaceae family, which is part of the Thermoproteota phylum comprising hyperthermophilic members widespread in geothermal environments. MAG002 consisted of 1.3 Mbp, distributed into 48 contigs with 1504 predicted coding sequences, had an average GC content of 41.3%, a completeness and contamination rate of 98.7% and 2.6%, respectively, and branched phylogenetically between the Ignisphaera and Zestosphaera lineages. Digital DNA‐DNA hybridization values compared with Ignisphaera aggregans and Zestosphaera tikiterensis were 33.7% and 19.4%, respectively, suggesting that this MAG represented a novel species and genus. Its 16S rRNA gene contained a large 421 bp intron. It encodes a complete gluconeogenesis pathway involving a bifunctional fructose‐1,6‐bisphosphate phosphatase/aldolase; however, the glycolysis pathway is incomplete. The ribulose monophosphate pathway enzymes could be used for pentose synthesis. MAG002 encodes several hydrogen‐evolving hydrogenases, with possible roles as hydrogen sinks during fermentation. We propose the name Zestomicrobium tamdykulense gen. nov. sp. nov. for this organism; it is the first thermophilic genome reported from Tajikistan.