Publications

4603

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.

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.

‘ Candidatus Liberibacter asiaticus’ ( C Las), the causal agent of citrus huanglongbing, is transmitted by the Asian citrus psyllid Diaphorina citri . While C Las-positive ( C Las+) females exhibit increased fecundity and metabolic demands, their neuroendocrine regulation mechanisms remain unclear. We propose C Las manipulates dopamine (DA) signaling to enhance psyllid fecundity and C Las proliferation. Metabolomics revealed elevated DA in C Las+ females. Silencing DA synthesis genes and receptor DcDop2 via RNAi reduced lipid reserves, fecundity, and ovarian C Las titers. Through combined in vivo and in vitro experiments, we demonstrated that the microRNA miR-31a suppresses DcDop2 expression by binding to its 3’ untranslated region. Overexpression of miR-31a resulted in decreased DcDop2 expression and C Las titers in the ovaries, eliciting phenotypic defects akin to DcDop2 knockdown. Furthermore, DcDop2 knockdown and miR-31a overexpression reduced juvenile hormone (JH) levels and adipokinetic hormone (AKH) signaling in fat bodies and ovaries. Consequently, C Las regulates the DA- DcDop2 signaling axis to improve D. citri lipid metabolism and fecundity, while simultaneously promoting its replication. These findings reveal a coevolution between C Las proliferation and ovarian development in the insect host. This discovery enhances our understanding of the molecular interplay between plant pathogens and vector insects and offers novel targets and strategies for HLB field management.

‘ Candidatus Liberibacter asiaticus’ ( C Las), the causal agent of citrus huanglongbing, is transmitted by the Asian citrus psyllid Diaphorina citri . While C Las-positive ( C Las+) females exhibit increased fecundity and metabolic demands, their neuroendocrine regulation mechanisms remain unclear. We propose C Las manipulates dopamine (DA) signaling to enhance psyllid fecundity and C Las proliferation. Metabolomics revealed elevated DA in C Las+ females. Silencing DA synthesis genes and receptor DcDop2 via RNAi reduced lipid reserves, fecundity, and ovarian C Las titers. Through combined in vivo and in vitro experiments, we demonstrated that the microRNA miR-31a suppresses DcDop2 expression by binding to its 3’ untranslated region. Overexpression of miR-31a resulted in decreased DcDop2 expression and C Las titers in the ovaries, eliciting phenotypic defects akin to DcDop2 knockdown. Furthermore, DcDop2 knockdown and miR-31a overexpression reduced juvenile hormone (JH) levels and adipokinetic hormone (AKH) signaling in fat bodies and ovaries. Consequently, C Las regulates the DA- DcDop2 signaling axis to improve D. citri lipid metabolism and fecundity, while simultaneously promoting its replication. These findings reveal a coevolution between C Las proliferation and ovarian development in the insect host. This discovery enhances our understanding of the molecular interplay between plant pathogens and vector insects and offers novel targets and strategies for HLB field management.

Understanding plant-vector-pathogen interactions is essential for explaining the persistence of stolbur diseases associated with the plant pathogenic bacterium ‘ Candidatus Phytoplasma solani’ (CaPsol) in agroecosystems. This study investigates the role of crop-associated Reptalus planthoppers (Insecta: Hemiptera: Cixiidae) in shaping CaPsol epidemiology within a four-crop rotation system (sunflower, wheat, sugar beet, and maize) in Serbia under field and experimental conditions. Over a three-year period (2023–2025), nymphal surveys, adult monitoring, emergence-cage experiments, molecular identification of planthoppers, assessment of CaPsol in crops, and vector transmission assays were conducted, with a particular focus on the sunflower-wheat sequence. Sunflower was identified as a developmental host for Reptalus quinquecostatus and Reptalus panzeri , with high CaPsol infection rates detected in both the host plant and associated vectors. In contrast, wheat appeared to primarily support nymphal overwintering, while its significance as a CaPsol reservoir remains inconclusive. Furthermore, the maize-wheat sequence supported the development of R. quinquecostatus while confirming its role in the life cycle of R. panzeri . Experimental trials demonstrated efficient CaPsol transmission to sunflower but limited transmission to wheat. Despite high infection levels under field conditions, sunflower remained asymptomatic, suggesting its role as a cryptic pathogen reservoir. The findings indicate that the sunflower-wheat sequence may sustain CaPsol-infected Reptalus spp. populations across seasons, facilitating pathogen persistence within cropping systems. The study highlights the importance of integrating vector life cycle dynamics into epidemiological frameworks of stolbur diseases, particularly in crop rotations where major cultivated hosts may support in-field CaPsol pathosystems.

Chokecherry (Prunus virginiana L.) is a native shrub that is widely found across North America and is a host of ‘Candidatus Phytoplasma pruni’ associated with X-disease of stone fruits. This pathogen is of major concern to U.S. cherry and peach growers, with the most recent and ongoing outbreak in the Pacific Northwest causing major economic harm. To investigate the role of chokecherry as a potential reservoir and source of orchard-associated strains, we surveyed wild chokecherry trees across 12 U.S. states, and compared the strains present to those in commercially cultivated Prunus species. Approximately 47% of chokecherry sampled tested positive for a ‘Ca. P. pruni’-related strain and phylogenetic analysis revealed high strain diversity, including six distinct clades and four newly identified lineages. In contrast, ‘Ca. P. pruni’ strains isolated from cultivated cherry and peach trees exhibited lower diversity and were infected by known disease outbreak-associated strains such as NWX. These data suggest limited transmission between wild and cultivated hosts in the western U.S., with patterns indicating spillover from orchards into nearby chokecherry populations rather than the reverse. However, in states east of the Rocky Mountains, chokecherry likely functions as a reservoir for orchard infections.