Publications

4535

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.

‘Candidatus Liberibacter asiaticus’ (CLas), the agent associated with the Huanglongbing citrus disease, is commonly detected using quantitative PCR (qPCR) with hydrolysis probes. Internal standards are typically included in the qPCR assays to reduce the risk of false negatives caused by inhibitors. When the internal standard is detected but CLas is not, it is generally assumed that the pathogen is absent from the tested sample. However, our study shows that trace amounts of CLas may go undetected if the internal standard is either overly abundant or too dissimilar to CLas. To overcome these limitations, we developed a synthetic internal standard (IS) that uses the same primer as the CLas target sequence, along with three to four downstream nucleotides, but with a unique internal sequence derived from smooth hammerhead shark (Sphyrna zygaena; IS-SHK). This sequence matches the guanine-cytosine content and melting temperature of the CLas target and was specifically selected to minimize potential interference from other nucleic acid materials in citrus samples. To minimize competition between the IS-SHK standard and the CLas target, an average of only 21 molecules of IS-SHK standard is added to each qPCR reaction. Therefore, when IS-SHK standard is detected at expected levels and CLas is not, the absence of CLas is confirmed rather than inhibition of the detection. Conversely, the absence of both IS-SHK standard and CLas suggests the presence of a qPCR inhibitor, warranting retesting of the sample.

ABSTRACTSesame phyllody, a destructive disease caused by phytoplasma infection, induces severe morphological abnormalities, including floral virescence, phyllody, witches' broom, leaf deformation, and stunted growth. This study aimed to characterize phytoplasma isolates from diverse regions of India, identifying them as Candidatus Phytoplasma asteris (16Sr‐I), Candidatus Phytoplasma citri (16Sr‐II), and Candidatus Phytoplasma australasia (16Sr‐II). Whole‐genome sequencing of Candidatus Phytoplasma asteris isolate SPGN revealed a genome size of 563,754 bp, encoding 542 proteins, including several genes associated with antibiotic resistance. Effector prediction analysis identified key virulence‐associated proteins, such as SAP50‐like, SAP34‐like, TENGU‐su inducer, and immunodominant membrane proteins, which manipulate host development and immune responses. Transcriptomic analysis of infected sesame plants revealed significant gene expression alterations, with upregulated genes linked to floral malformation, vascular tissue modifications, and stress responses, while the downregulated genes were associated with flavonoid metabolism and immune signaling. Phytoplasma infection disrupted hormonal pathways, leading to increased expression of auxin, cytokinin, and gibberellin‐related genes, suggesting hormonal dysregulation as a key factor in symptom development. Furthermore, immune suppression was evident through the downregulation of key defense‐related genes, including those involved in MAPK signaling and pathogenesis‐related protein families. These findings enhance our understanding of phytoplasma pathogenesis in sesame and provide potential targets for developing effective disease management strategies.

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 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.

Abstract Autophagy, a cellular process involved in the degradation and recycling of cellular components, has emerged as a pivotal mechanism for maintaining cellular homeostasis and combating pathogen invasion. Here, we provide evidence that the overexpression of CsATG8c inhibits CLas proliferation in citrus. CsATG8c directly interacts with the CLas effector protein SDE4040, leading to its degradation via the autophagic pathway. The SDE4040 protein acts as a virulence effector, and transgenic citrus plants expressing SDE4040 promote CLas proliferation by suppressing the hypersensitive response (HR) of the host and reducing the levels of jasmonic acid (JA). Collectively, these results demonstrate that ATG8-mediated selective autophagy limits CLas infection by degrading a virulence effector protein, which provides the first evidence for the role of autophagy in combating CLas infection.