Publications

4618

Abstract ‘ Candidatus Liberibacter solanacearum’ (Lso) is a devastating bacterial pathogen of crops transmitted by psyllids. Previously, a link between changes in ubiquitination and the progression of diseases caused by Lso was established. Among the Lso haplotypes, LsoA and LsoB infect solanaceous crops. LsoA induces chlorosis and stunting in tomato, while LsoB infection leads to more severe symptoms, including plant death. To better characterize the molecular basis of the differences in the diseases caused by these haplotypes, we cataloged the ubiquitinome of tomato leaves four weeks after LsoA and LsoB-infection and following infestation with Lso-free psyllids. Our analysis revealed haplotype-specific changes in the plant ubiquitinome. Gene Ontology (GO) terms related to glucose metabolism and proteasome-mediated ubiquitin-dependent protein catabolism were enriched among the differentially ubiquitinated proteins between LsoA-infected and Lso-free infested plants. Additionally, a KEGG pathway analysis determined an overrepresentation of proteins involved in carbon metabolism and fixation via the Calvin cycle. In contrast, the comparison of LsoB-infected and Lso-free infested plants revealed a broader range of enriched GO terms and KEGG pathways, including those associated with carbohydrate and energy metabolism, proteasome activity, and oxidative stress. These results contribute to our understanding of the development of Liberibacter-related diseases and reveal the importance of ubiquitin-related pathways in Lso infection. They also contribute to the expanding inventory of ubiquitinated proteins.

The bois noir (BN) disease of grapevines is widespread in German winegrowing regions. It is associated with ‘Candidatus Phytoplasma solani’, which affects not only grapevines but also other wild and cultivated plants. This pathogen has a complex epidemiology including different insect vectors and various host plants. A study was carried out to investigate the genetic variability of ‘Ca. P. solani’ in different winegrowing regions in Germany. Between 2017 and 2023, samples of grapevine, stinging nettle, bindweed, and other herbaceous plants as well as specimens of different planthopper species colonizing viticultural habitats were analyzed for infection with ‘Ca. P. solani’. All positive tested samples were further characterized by multilocus sequence typing (MLST) based on the genes tuf, stamp, secY, and vmp1. The genetic variability was assessed by RFLP analyses of the tuf and vmp1 PCR products, coupled with sequencing of the stamp and secY amplification products. A total of 1274 grapevines, 35 bindweed, and 18 stinging nettle samples were infected with ‘Ca. P. solani’ but also five samples of other weed species. Among the known and putative insect vectors, specimens of Hyalesthes obsoletus, Reptalus spp., and Dictyophara europaea harbored the phytoplasma. In both plants and insects, two genotype combinations were predominantly associated with the classical bindweed and stinging nettle cycle, respectively. The MLST analysis revealed considerable differences between German isolates and data reported from other European regions and new genotype combinations were identified, indicating new host plant–vector associations.

‘Candidatus Liberibacter asiaticus’ (CLas) is a devastating pathogen of citrus associated with Huanglongbing (HLB, citrus greening disease). HLB is economically significant in Asia and has destroyed millions of citrus trees worldwide during the last century. Since 2007, when the first molecular evidence for the presence of CLas in North-West Frontier Province of Pakistan (Khyber Pakhtunkhwa) were presented, there have been a limited number of studies reporting the pathogen in different citrus growing districts of the Punjab Province, one of the major citrus producing areas of the country. In this study, a small-scale survey was conducted in citrus groves exhibiting HLB-like symptoms in different districts of Punjab Province. The aim was to obtain current information on the incidence of CLas in the area and complement the previous studies. Conventional and real time quantitative polymerase chain reaction (PCR and qPCR) assays were used for the detection of CLas in the 94 samples tested, followed by sequencing of the PCR amplicons. Overall CLas was detected in 43% (40/94) of the tested samples from Kinnow mandarin (n= 22), sweet orange (n= 12), grapefruit (n= 3) and Feutrell’s early mandarin (n= 3). In agreement with previous reports, this survey confirmed the presence of HLB in the Punjab Province of Pakistan and provided updated molecular evidence for the presence of CLas and disease incidence for four citrus cultivars from five citrus growing districts of the province.

Citrus huanglongbing (HLB), caused by ‘Candidatus Liberibacter asiaticus’ (CLas), is a destructive disease threatening global citrus industry. Although citrus cultivars differ in HLB sensitivity, how infection alters endophytic bacterial communities in cultivars with contrasting susceptibility remains unclear. Here, we compared endophytic microbiome shifts in leaf and root tissues of HLB-susceptible Shatangju mandarin (Citrus reticulata cv. Shatangju) and HLB-tolerant Shatian pomelo (C. maxima cv. Shatian) at 10 months postgrafting with CLas-infected buds. Infected Shatangju mandarin showed severe symptoms and higher CLas levels in leaves than in roots, while infected Shatian pomelo remained asymptomatic with higher CLas in roots than in leaves. High-throughput 16S rRNA gene sequencing revealed that CLas infection restructured the endophytic microbial community in a tissue-specific manner. CLas-infected Shatian pomelo leaves displayed increased microbial diversity and network complexity, while CLas-infected Shatangju mandarin roots harbored more disease-suppressive taxa like Streptomyces. Across both cultivars, network complexity correlated inversely with CLas abundance. Key genera (e.g., Pseudomonas, Streptomyces, and Prevotella) correlated positively with CLas, suggesting roles in mitigating pathogen effects. Predicted functional profiling indicated activated pathways (amino acid metabolism, terpenoid/polyketide biosynthesis, and xenobiotic biodegradation) potentially supporting host defense in infected tissues. The HLB tolerance of Shatian pomelo appeared linked to tissue-specific bacterial restructuring, particularly recruitment of antibiotic-producing bacteria and enhanced metabolic resilience. These findings elucidated cultivar-specific microbial strategies against CLas, offering insights for microbiome-mediated HLB management.

'Candidatus Phytoplasma solani' is a distinct species of the class Mollicutes (16SrXII group), characterized by phloem-limited localization and strong host dependence. It is widely distributed, mainly in Europe, and affects over 100 plant species, including economically important crops for Moldova. The name reflects its significant impact on plants of the Solanaceae family, causing stolbur disease. It also infects grapevine, pepper, maize, lavender, and other crops. Climate change has favored the spread of the pathogen and its insect vectors into new regions and host plants. Therefore, monitoring and controlling its dissemination in economically important crops is essential. Accurate diagnosis can be achieved by molecular methods, with PCR-based techniques offering a reliable and cost-effective approach. The aim of the study was to determine the presence or absence of infection in some agricultural crops: tomato, maize, potato, pepper, eggplant, wheat, plum and apple growing in experimental fields of Institute of Genetics, Physiology and Plant Protection, MSU. Materials and methods: Various DNA extraction methods were used depending on plant culture: boiling in alkaline solution, DNAzol, SDS, CTAB. Nested PCR analysis was carried out using specific to 'Ca. P. solani' primers designed on the base of chaperonine or 16S rRNA gene sequences. Amplification results were recorded using gel agarose electrophoresis (1.5% agarose, 0.5 x TBE buffer) stained with ethidium bromide and visualized in UV. Results: A comprehensive study of tomato conducted during 2016-2025 showed the continuous presence of the pathogen, with infection rates reaching up to 72% depending on annual conditions, confirming the high susceptibility of tomato to 'Ca. P. solani'. In potato, 14.6% of plants were infected, while sweet pepper showed a much lower incidence of 4%. Overall, the results indicate the predominant distribution of the pathogen within the Solanaceae family, further supported by its detection in the ruderal species Solanum nigrum. The phytoplasma was not detected only in eggplant among the analyzed Solanaceae species. In contrast, molecular diagnostics gave negative results in crops from other families, including maize and wheat (cereals), as well as apple and plum (fruit crops). The pathogen was not detected in orchard trees during either the dormant or fruit-bearing stages. Conclusions: Thus, obtained results demonstrate an ecological and epidemiological specificity of 'Ca. P. solani' for certain host species, characterized by a high incidence in Solanaceae, particularly tomato. Additionally, the study confirms the potential role of ruderal species within the same family as natural reservoirs of the pathogen. These data contribute to a deeper understanding of the spread of the phytoplasma providing a base for effective monitoring and phytosanitary management strategies.

ABSTRACT Background Data on feline hemotropic mycoplasmas is limited in Iran. Aim. The aim of this study was to investigate the infection rate of cats with this pathogen in Mashhad,Iran and evaluate its assosiation with cliniopathological changes. Materias & Methods Blood samples from 100 cats presenting at veterinary clinics were analysed for Mycoplasma haemofelis (Mhf) and Candidatus Mycoplasma haemominutum (CMhm). Samples were screened for hemotropic mycoplasmas using microscopic examination and conventional polymerase chain reaction (PCR). Samples were also subjected to haematological and biochemical analysis. Results Microscopic examination detected hemotropic mycoplasmas in 65% of samples, whereas PCR identified a 23% infection rate, with 65.21% ( n  = 15) positive for CMhm and 34.78% ( n  = 8) for Mhf. The presence of Haemomycoplasma DNA was significantly associated with age, gender, breed and roaming status ( p  < 0.05). Infected cats exhibited significant alterations ( p  < 0.05) in haematocrit (Hct), red blood cell count (RBC), haemoglobin (HGB), white blood cell count (WBC), neutrophil counts, serum total protein (TP), globulin, phosphorus (Pi), aspartate aminotransferase (AST) levels and the albumin/globulin ratio (AGR). Conclusions Our study highlights a high prevalence of feline hemoplasmosis in northeastern Iran, with CMhm as the predominant species. Key risk factors included male gender, adult, outdoor access and domestic short hair (DSH) breed. Although infected cats showed consistent clinicopathologic changes, no differences were observed between Mhf and CMhm infections.