Publications

4619

Abstract Background ‘ Candidatus Liberibacter solanacearum’ (Lso) is a phloem-limited bacterial pathogen causing significant diseases in solanaceous crops. In the United States, haplotypes A and B are transmitted by the potato psyllid Bactericera cockerelli . We previously identified differences in their acquisition and transmission between adults and nymphs. The present study characterized the dynamics of LsoA and LsoB acquisition and transmission by nymphs and examined the transcriptional responses of the nymphal gut upon their acquisition. Methods and results Nymphs were exposed to LsoA- or LsoB-infected plants for 1, 3, 5, or 7 days to measure the bacterial accumulation and for 8 days to assess the transmission efficiency following sequential inoculation of tomato plants. Quantitative PCR showed that LsoB accumulated to higher levels than LsoA after 3 days of acquisition. Following the sequential inoculation, LsoB was transmitted earlier than LsoA indicating a shorter latency period. RNA-seq analysis of the guts following a 1- and 5-day acquisition access periods revealed a greater transcriptional regulation at 5 days than at 1 day. Furthermore, the responses were haplotype-specific: LsoA primarily affected genes involved in protein translation, ER stress, and cell cycle regulation, whereas LsoB regulated genes involved in autophagy, apoptosis, and immune pathways. Conclusions This study revealed haplotype-specific gene regulation potentially leading to LsoB being transmitted more efficiently by psyllid nymphs.

Background: The Asian Haemaphysalis longicornis is capable of transmitting a wide range of zoonotic pathogens. This study aimed to investigate the prevalence and characteristics of major pathogens in questing H. longicornis ticks collected from two geographically and ecologically distinct regions in China. Methods: A total of 1004 questing H. longicornis ticks were collected from Liaoning Province (Northeast China; n = 882) and Anhui Province (Central and Eastern China; n = 122) and pooled into 670 mixed samples. Tick species were identified by mitochondrial cytochrome oxidase I gene sequencing. Nucleic acid samples from all pools were first screened for Dabie bandavirus using RT-PCR and for bacteria using universal 16S rRNA primers. Bacteria-positive samples were further tested using polygenic seminested PCR for Rickettsia spp. and Coxiella -like endosymbionts (CLEs). Phylogenetic analyses, including polygene sequence analysis, were performed to ensure the accuracy of species identification and to explore genetic relationships. Results: No Dabie bandavirus was detected in any samples. Among the 670 tick pools, 14 were positive for spotted fever group rickettsiae (SFGR), with an overall minimum infection rate (MIR) of 1.4% (14/1004). Notably, the detected SFGR species showed clear geographic segregation: Candidatus Rickettsia jingxinensis was detected only in Liaoning Province (MIR of 1.4%), while Rickettsia heilongjiangensis was found exclusively in Anhui Province (MIR of 1.6%). Additionally, CLEs (overall MIR of 2.0%) were identified in 20 tick pools, with a significantly higher prevalence in Anhui Province (10.7%) than in Liaoning Province (0.8%; p < 0.001). Conclusions: This surveillance revealed a distinct geographical distribution pattern of SFGR species in H. longicornis populations in China and confirmed the presence of Ca . R. jingxinensis in the northeast and R. heilongjiangensis in the central and eastern regions. These findings, supported by polygenic evidence, provide essential epidemiological data for understanding regional tick-borne disease risks and highlight the need for continued region-specific surveillance.

Abstract Bovine hemoplasmas, including Mycoplasma wenyonii (M. wenyonii) and Candidatus Mycoplasma haemobos (C. M. haemobos) , are vector-borne pathogens that can cause significant clinical diseases in cattle. This case report from Türkiye describes the clinical findings, hematological analysis, and serum biochemistry results of a cow presenting with hemoglobinuria caused by C. M. haemobos . Blood samples from the infected animal were analyzed using hematological, biochemical, microscopic, and molecular methods. Multiplex polymerase chain reaction assay confirmed the infection, and microscopic analysis revealed a parasitemia rate of 6.99%. Clinical signs included hemoglobinuria, icterus, and anemia. The treatment included fluid therapy, antibiotic (oxytetracycline), and antianemic drugs. The cattle died 1 month post-treatment, reportedly due to a lower respiratory tract infection. This case report describes the diagnostic methods, clinical findings, and laboratory results. A widescale molecular survey of C. M. haemobos in cattle is warranted, with investigation of its pathogenicity and pathogenies.

Abstract “ Candidatus Liberibacter solanacearum” (Lso) is a phloem-limited bacterial pathogen transmitted by psyllid. In the USA, the haplotypes A and B are transmitted by the tomato psyllid, Bactericera cockerelli, and are responsible for economic damage to the solanaceous crop industry. In tomato, haplotypes A and B cause diseases with differing degrees of severity, yet their underlying mechanisms are not well understood. The role that abiotic stress plays in disease development has not been characterized. In the present study, we evaluated whether water stress influenced the development of symptoms associated with these haplotypes in tomato ( Solanum lycopersicum “Moneymaker”). First, pot-grown tomato plants were subjected to either a control or a water-stress regime, then they were assigned to one of three infection treatments (Lso-free, LsoA, or LsoB) under laboratory-controlled conditions. Symptom development was monitored for up to 8 weeks following infection. Results of this experiment revealed that water stress significantly reduced the plant water potential and was the primary driver of reduced height, with infection only having an effect in later weeks. Water stress also increased the detectability of Lso throughout the plant and across three timepoints (weeks 4, 6, and 8 after infection). This increase in Lso-positive tissues suggests that water stress creates a more homogenous distribution of Lso throughout the plant. More noticeably, water stress significantly reduced the severity of the disease associated with haplotype A but not B. Overall, these findings revealed the existence of haplotype-specific interactions between Lso infection and water stress on the tomato health. This work highlights the influence of abiotic factors on plant health.

Ticks are important vectors of bacteria belonging to the order Rickettsiales, several of which are causes zoonotic diseases. Amblyomma triste is the main vector of Rickettsia parkeri , the etiological agent responsible for most cases of human spotted fever rickettsiosis in Argentina. However, information on the circulation of rickettsial agents in protected areas of the La Plata River Hydrographic Basin, a region that includes highly urbanized environments and frequent contact between wildlife, domestic animals and humans, remains limited. The aim of this study was to investigate the presence of rickettsial bacteria in A. triste collected in protected areas of Buenos Aires Province, (La Plata River Hydrographic Basin, Argentina). Between September and December 2021, ticks were collected by vegetation flagging in four protected areas and analyzed individually. Polymerase chain reactions (PCR) for detecting the genus Rickettsia was initially performed using a simple PCR to amplify a variablesized fragment of the 23S-5S rRNA intergenic spacer. An initial PCR was performed with primers for a 16S rRNA fragment for the Anaplasmataceae family. A total of 247 adult ticks were examined. Twelve specimens (4.9%) tested positive for Rickettsia , and sequence analysis confirmed their identity as R. parkeri . Positive ticks were detected in Ciervo de los Pantanos National Park and Campos del Tuyú National Park. In addition, two specimens yielded sequences corresponding to Candidatus Midichloria sp. These findings confirm the presence of R. parkeri in A. triste populations from protected areas of the La Plata River Hydrographic Basin and provide the first evidence of Ca. Midichloria sp. in this tick species in Argentina. The results highlight the need for continued surveillance of tick-borne microorganisms in protected areas located near densely populated regions, where human exposure to infected ticks may occur.

The Asian citrus psyllid, Diaphorina citri, transmits the putative causal agent of citrus greening disease, ‘ Candidatus Liberibacter asiaticus’. The transmission occurs in a propagative, circulative manner. Specific protein–protein interactions are required for the accomplishment of the transmission process. We employed the far-Western technique, also known as protein overlay assay, and mass spectrometry to identify D. citri proteins that specifically recognize membrane proteins of ‘ Ca. L. asiaticus’. Whole-body protein extracts of D. citri were separated by electrophoresis and blotted onto polyvinylidene difluoride membranes. The membranes were overlayed with sonicated leaf midrib extracts from ‘ Ca. L. asiaticus’-infected citrus plants. The protein complexes were detected using different antibodies against ‘ Ca. L. asiaticus’ membrane proteins and peptidoglycans associated with lipoproteins. By comparison, spots were extracted from a polyacrylamide gel for liquid chromatography-tandem mass spectrometry analysis. Identified proteins included ATP synthase alpha and beta subunits, actin, alpha- and beta-tubulins, transitional endoplasmic reticulum ATPase TER94, 78 kDa glucose-regulated protein, and arginine kinase. These findings emphasize the involvement of energy machinery and muscle proteins in the ‘ Ca. L. asiaticus’– D. citri interactions. Understanding the pathogen–vector interactions will lead to better-designed control strategies based on the interference with specific interactions and/or blocking transmission.