Publications

4634

Abstract Background Candidatus Phytoplasma infection is among the most destructive plant diseases, characterized by phyllody, witches broom, virescence etc. Sesame (Sesamum indicum L.), one of the oldest cultivated oilseed crops, valued for its nutritional and medicinal properties, is highly susceptible to phytoplasma infection, causing substantial annual yield losses. The present study aimed to investigate the metabolomic and molecular alterations in sesame plants as a consequence of phytoplasma infection in two distinct tissue types, leaves and flowers, using a multi-omics approach. Results The study revealed that phytoplasma infection significantly alters the expression of floral homeobox and meristem identity genes in an antagonistic manner, resulting in the development of leaf-like traits in floral tissues. Integrated analyses of transcriptomic and metabolomic datasets showed that control leaves, control flowers, infected leaves, and infected flowers each displayed distinct metabolomic and transcriptomic profiles. Metabolomic profiling demonstrated major changes in pathways such as porphyrin metabolism, brassinosteroid metabolism, and phenylpropanoid biosynthesis. Complementary KEGG pathway enrichment analysis of transcriptome data confirmed strong enrichment of secondary metabolite biosynthesis in both tissue types upon infection. Tissue-specific responses were evident. Floral tissues accumulated green pigments due to increased porphyrin biosynthesis and reduced degradation, while leaves showed simultaneous upregulation of both biosynthesis and breakdown pathways of porphyrins. Floral tissues exhibited stronger stress-associated responses, including upregulation of genes related to stress enzymes, phenylpropanoids, and lignification-related metabolites. In contrast, certain compounds such as lignans were specifically accumulated in leaves upon infection. These observations were further supported by biochemical, histological, and qRT-PCR assays. Conclusion This study provides the first clear evidence of tissue-specific metabolic reprogramming in sesame under Ca. Phytoplasma infection through integrated transcriptomic and metabolomic analyses. These findings improve our understanding of host-pathogen interactions and offer a basis for strategies to reduce phytoplasma-induced yield losses.

ABSTRACT Insects of the suborder Auchenorrhyncha harbour multiple ancient endosymbionts that jointly produce essential nutrients lacking from the host's diet. Compared to cicadas, leafhoppers, and spittlebugs, our understanding of the multipartite symbioses among planthoppers, an extremely diverse insect group, is still very limited. Herein, we assembled the genomes of the primary endosymbionts of two planthopper species from the Cixiidae family, Cixius wagneri and Pentastiridius leporinus , both vectors of phytopathogenic Arsenophonus in Europe. Each species harboured a different tripartite endosymbiont consortium: while P. leporinus carried the well‐known combination ‘ Candidatus Karelsulcia muelleri’, ‘ Ca . Vidania fulgoroideae’, and ‘ Ca . Purcelliella pentastirinorum’, C. wagneri harboured a yet unknown Gammaproteobacterium in addition to Karelsulcia and Vidania . This new endosymbiont ‘ Ca . Mirabilia symbiotica’ is likely much older than Purcelliella , considering its extremely reduced genome. In both species, Karelsulcia and Vidania jointly produce the 10 essential amino acids, whereas Purcelliella and Mirabilia provide the non‐essential amino acid cysteine and slightly different gene sets encoding B vitamins. Our findings confirm the functional stability of multipartite planthopper endosymbiont consortia despite changing partners over evolutionary time. In addition, we describe a new Rickettsia strain from the Meloidae group colonising P. leporinus , highlighting the diversity of bacterial endosymbionts associated with planthoppers.

The prokaryotic generic names Bogoriella Groth et al. 1997 and Stella Vasilyeva 1985 are illegitimate because they are later homonyms of the genus names Bogoriella Zahlbr. 1928 (Ascomycota) and Stella Massee 1889 (Basidiomycota) (Principle 2 and Rule 51b(4) of the International Code of Nomenclature of Prokaryotes). We therefore propose the replacement names Allobogoriella gen. nov., Allobogoriella caseilytica comb. nov., Allobogoriellaceae fam. nov., Allobogoriellales ord. nov., Allostella gen. nov., Allostella humosa comb. nov. and Allostellaceae fam. nov. as replacement names for the illegitimate prokaryotic names Bogoriella, Bogoriella caseilytica, Bogoriellaceae, Bogoriellales, Stella, Stella humosa, Stella vacuolata and Stellaceae, respectively.

AbstractBACKGROUNDAutophagy is a conserved mechanism by which eukaryotic organisms defend against pathogen infection. However, the molecular mechanisms underlying the role of autophagy in the interactions of insect vectors with the phloem‐limited bacterial pathogen remain unclear. The citrus Huanglongbing (HLB)‐associated pathogen ‘Candidatus Liberibacter asiaticus’ (CLas) seriously endangers development of the citrus industry. It spreads via Diaphorina citri in a persistent and propagative manner.RESULTSIn this study, a total of 30 autophagy‐related genes (ATG) were identified in the D. citri genome, among which multiple genes were significantly regulated after CLas infection. Concurrently, CLas infection also leads to an increased number of autophagosomes and enhanced accumulation of ATG8‐II. Ultrastructural observations revealed the presence of bacterial‐like structures within autophagosomes in the midgut of CLas‐infected D. citri. Furthermore, both activation and inhibition of autophagy significantly influenced CLas titers. However, autophagy cannot completely eliminate CLas in D. citri. We identified a CLas effector, SDE4040 (CLIBASIA_04040), that interacts with DcATG8 and co‐localizes on autophagosomes in D. citri. Co‐expression of SDE4040 and DcATG8 induces autophagy in Spodoptera frugiperda (Sf9) cells.CONCLUSIONTaken together, these results indicate that CLas infection activates the autophagy pathway in D. citri, contributing to a reduction in bacterial titer. Our data also revealed that CLas may trigger complex interactions with the insect. © 2025 Society of Chemical Industry.

Abstract Citrus greening disease, caused by ‘Candidatus Liberibacter asiaticus’, severely impacts citrus production worldwide. The development of sustainable control strategies for this disease is restricted by the unavailability of the bacterium in pure culture. Herein, the metabolic profile of the waxworm larvae, Galleria mellonella, was compared to that of Diaphorina citri, the vector of ‘Ca. L. asiaticus’. Our findings showed that G. mellonella larvae possess the nutritional needs to host ‘Ca. L. asiaticus’, supporting its short-term persistence, and responds to infection with a visible immune reaction by producing melanin upon bacterial invasion. The inoculated larvae exhibit detectable bacterial titers for up to four days when inoculated with infected citrus phloem sap or D. citri haemolymph, after which bacterial titers decline, and infected larvae show reduced survival compared to mock-treated and ‘Ca. L. asiaticus’-free controls. Metabolic profiling of G. mellonella, D. citri, and honeybees (Apis mellifera) reveals distinct chemical compositions in their haemolymph. G. mellonella contains higher levels of amino acids, organic acids, nucleotides, and sugar-nucleotides, providing essential nutrients for ‘Ca. L. asiaticus’, while D. citri is enriched in monosaccharides and sugar-alcohols. Citric acid was detected exclusively in the haemolymph of G. mellonella. These findings suggest G. mellonella as a convenient model that can transiently host ‘Ca. L. asiaticus’ for short-term use, which would facilitate high-throughput screening of antimicrobial compounds against ‘Ca. L. asiaticus’, as well as exploring host-pathogen interactions. This model could accelerate the development of effective treatments against citrus greening and inform broader strategies for managing vector-borne plant diseases.