Publications

4466

Cottony ash psyllid (CAP, Psyllopsis discrepans) is an important, invasive insect pest of ash trees in North America, where it has established populations and is the host of a newly identified strain of ‘ Candidatus Liberibacter solanacearum’. However, not much is known about the diversity of its introduced population. In this study, a CAP mitochondrial genome (mitogenome) sequence was obtained from a collection in Saskatoon, Saskatchewan, Canada. The CAP mitogenome is a circular DNA of 18,824 bp, encoding 13 protein-coding genes, 21 transfer RNA genes, and two ribosomal RNA genes. BLAST search using the CAP mitogenome as a query against the GenBank sequence database showed the mitogenome of Euphyllura phillyreae (15,202 bp) was the most similar (query coverage = 77%; percentage identity = 78.90%). The CAP mitogenome is significantly different from other known psyllid mitogenomes with the presence of a 4,357-bp control region. The mitogenome sequence will further the genomic understanding of CAP. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

‘Candidatus Phytoplasma ulmi’ (16SrV-A) is the causal agent of elm yellows (EY), a lethal and/or decline disease of several Ulmus (elm) species and hybrids in North America and Europe. In this study, field observations and PCR assays were used to detect phytoplasma infections in diseased U. minor, U. pumila and U. glabra trees in southern Italy. Also, a multigene sequence analysis employing various less conserved genes was carried out to explore the genetic variation in detected strains. All the symptomatic elm trees tested were infected with ‘Ca. Phytoplasma ulmi’. No other phytoplasmas or variants could be detected. Although ‘Ca. Phytoplasma ulmi’ was already known to occur in southern Italy on European field elm, the current work expands the information on the presence, disease incidence and severity, plant host range and molecular aspects of EY phytoplasma strains occurring in southern Italy. In addition, this is the first report from Italy on the molecular characterization of EY phytoplasma strains through map, imp and groEL gene sequence and phylogenetic analyses. Among the newly detected EY phytoplasma strains, some proved distantly related to each other and to other previously characterized EY phytoplasma strains within the genes examined. This implies the presence of distinct taxonomic entities within the material examined. The occurrence of different strains was not linked to the biological traits and geographical distribution. However, the data obtained may provide a basis for further studies aimed at elucidating several other unknown aspects of the EY agent, knowledge of which is essential for effective disease management and control strategies. The results of the current work also show that the EY phytoplasma is particularly widespread in southern Italy and is of considerable economic and ecological relevance.

Dehalobacter is a genus of organohalide-respiring bacteria that is recognized for its fastidious growth using reductive dehalogenases (RDases). In the SC05 culture, however, a Dehalobacter population also mineralizes dichloromethane (DCM) produced by chloroform dechlorination using the mec cassette, just downstream of its active RDase. A closed genome of this DCM-mineralizing lineage has previously evaded assembly. Here, we present the genomes of two novel Dehalobacter strains, each of which was assembled from the metagenome of a distinct subculture from SC05. A pangenomic analysis of the Dehalobacter genus, including RDase synteny and phylogenomics, reveals at least five species of Dehalobacter based on average nucleotide identity, RDase and core gene synteny, as well as differential functional genes. An integration hotspot is also pinpointed in the Dehalobacter genome, in which many recombinase islands have accumulated. This nested recombinase island encodes the active RDase and mec cassette in both SC05 Dehalobacter genomes, indicating the transfer of key functional genes between species of Dehalobacter. Horizontal gene transfer between these two novel Dehalobacter strains has implications for the evolutionary history within the SC05 subcultures and of the Dehalobacter genus as a whole, especially regarding adaptation to anthropogenic chemicals.

The order Caryophanales, belonging to class Bacilli, is globally distributed in various ecosystems. Currently, this order comprised 12 families that show vast phenotypic, ecological and genotypic variation. The classification of Caryophanales at the family level is currently mainly based on 16S rRNA gene sequencing analysis and the presence of shared phenotypic characteristics, resulting in noticeable anomalies. Our present study revises the taxonomy of Caryophanales based on 1080 available high-quality genome sequences of type strains. The evaluated parameters included the core-genome phylogeny, pairwise average aa identity, lineage-specific core genes, physiological criteria and ecological parameters. Based on the results of this polyphasic approach, we propose that the order Caryophanales be reclassified into 41 families, which include the existing 12 families, 17 families in a recent Validation List in the IJSEM (Validation List no. 215) and 12 novel families for which we propose the names Aureibacillaceae, Cytobacillaceae, Domibacillaceae, Falsibacillaceae, Heyndrickxiaceae, Lottiidibacillaceae, Oxalophagaceae, Pradoshiaceae, Rossellomoreaceae, Schinkiaceae, Sulfoacidibacillaceae and Sutcliffiellaceae. This work represents a genomic sequence-based and systematic framework for classifying the order Caryophanales at the family level, providing new insights into its evolution.

AbstractThe poinsettia (Euphorbia pulcherrimaWilld. ex Klotzsch.) is one of Turkey’s most important potted ornamental crops. Potted poinsettia plants exhibiting smaller-sized brilliant red bracts against the green leaves with free-branching were collected from commercial florists in three provinces of Turkey. In iPhyClassifier analysis, the query 16SrDNA sequences of our isolates shared 99.58% identity with that of theCandidatusPhytoplasma pruni. Our leaf samples consistently yielded a product of 0.7 kb by PCR with primers (KFD4F/KFD4R), which was newly designed based on X-Disease group (16SrIII) of phytoplasma secY sequences available in GenBank. The partial 16S rRNA sequences were used for phylogenetic analyses covering 41 taxa from the group of 16SrIII’Candidatus Phytoplasma’ strains, including 14 strains causing disease on poinsettia worldwide. The sequences that caused the same disease in poinsettia plants in Finland, the USA, Mexico, Taiwan, Japan, Korea, and Canada, including three strains from Turkey, formed a mono-phylogenetic group with a support value of 87%.

AbstractThe endosymbiont Candidatus Azoamicus ciliaticola was proposed to generate ATP for its eukaryotic host, an anaerobic ciliate of the Plagiopylea class, fulfilling a function analogous to mitochondria in other eukaryotic cells. The discovery of this respiratory endosymbiosis has major implications for both evolutionary history and ecology of microbial eukaryotes. However, with only a single species described, knowledge of its environmental distribution and diversity is limited. Here we report four complete, circular metagenome assembled genomes (cMAGs) representing respiratory endosymbionts inhabiting groundwater in California, Ohio, and Germany. These cMAGs form two lineages comprising a monophyletic clade within the uncharacterized gammaproteobacterial order UBA6186, enabling evolutionary analysis of their key protein complexes. Strikingly, all four cMAGs encode a cytochrome cbb3 oxidase, which indicates that these endosymbionts have the capacity for aerobic respiration. Accordingly, we detect these respiratory endosymbionts in diverse habitats worldwide, thus further expanding the ecological scope of this respiratory symbiosis.

The global citrus industry faces a great threat from Huanglongbing (HLB), a destructive disease caused by ‘Candidatus Liberibacter asiaticus’ (CLas) that induces significant economic losses without any known cure. Understanding how citrus plants defend against HLB, particularly at the early stages of infection, is crucial for developing long-term solutions. This study investigated the earliest metabolic responses of fresh citrus leaves to CLas infection using untargeted metabolomics and machine learning models. HLB-tolerant and HLB-sensitive cultivars were compared to analyze their biochemical reactions within 48 hours post-infection. HESI/Q-Orbitrap MS analysis identified temporal differential metabolites, revealing distinct metabolic pathways activated in response to CLas infection. Both cultivars responded by increasing specific metabolite concentrations, such as flavonoids, within 2 hours post-infection, but the HLB-tolerant cultivar maintained higher levels throughout the 48-hour period. This early metabolic activity could influence long-term plant health by enhancing disease resistance and reducing pathogen impact. These findings provide potential biomarkers for breeding HLB-resistant cultivars and offer valuable insights for developing sustainable management strategies to mitigate the impact of HLB on the citrus industry, ensuring its long-term productivity and economic viability.

ABSTRACT Huanglongbing (HLB) is a severe citrus disease in China caused by Candidatus Liberibacter asiaticus ( C Las). Since its initial identification, the pathogen has spread to 10 mainland provinces in China and caused devastating loss. Three distinct prophage types have been identified in C Las; however, their distribution and diversity in China remain inadequately understood. In this study, we collected 500 C Las samples from 10 provinces in China, employing three specific genomic loci to identify prophage types. Subsequently, Sanger sequencing was employed to analyze the genetic diversity of prophage within populations of C Las in China. In addition, the MaxEnt model optimized by the ENMeval software package, was used to predict the habitat suitability of populations of C Las and assess the potential impact of future climate change on its distribution in China. Our analysis revealed that type 2 prophage is the most prevalent, accounting for 55% in China. Among the 10 provinces tested, C Las populations in Yunnan and Sichuan demonstrated higher genetic diversity. Further analysis reveals that C Las populations harboring type 1 prophage remain relatively stable, whereas those carrying type 2 and type 3 prophages undergo population expansion. Furthermore, our predictive models indicate that the presently suitable habitat for C Las populations is concentrated in the southern and certain central regions of China, with an anticipated expansion under future climate change conditions. Presently, the center of populations of C Las characterized by favorable living conditions is situated in Zunyi City, Guizhou Province. Nevertheless, a projected trend indicates a shift toward the northeast, particularly targeting Tongren City in the foreseeable future. IMPORTANCE This study offers significant insights into the distribution and genetic diversity of three types of prophages associated with Candidatus Liberibacter asiaticus ( C Las) in China. Our predictions underscore the implications of climate change on the future distribution of C Las. These findings contribute to a better understanding of Huanglongbing management strategies and can facilitate the development of effective measures to control the spread of this devastating disease within the citrus industry.