Publications

4576

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 (PVDF) 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 LC-MS-MS 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 emphasized 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.

Abstract Magnetoreception is a remarkable ability found across a diverse range of organisms, including bacteria, birds, fish, insects, and mammals, enabling them to detect and harness the Earth’s geomagnetic field. Recently, the recruitment of biomineralizing ectosymbionts by euglenozoans was evidenced as an ecological strategy for microeukaryotes to acquire this sense. Here, we report a case of magnetosymbiosis involving a ciliate and four populations of endosymbiotic bacteria experiencing genome reduction. Among these bacteria, one group of sulphate-reducing Desulfovibrionales was found to biomineralize bundles of bullet-shaped magnetite crystals. The ciliate’s magnetotaxis mirrors that of free-living magnetotactic bacteria and euglenozoans, enabling efficient navigation in chemically stratified aquatic environments. However, in this case, magnetotaxis arises from an endosymbiotic interaction. Using a combination of optical-, confocal-, electron- and X-ray-based microscopy techniques, together with genomic analyses, these findings demonstrate that magnetosymbiosis can emerge in unicellular eukaryotic lineages through endosymbiotic integration, expanding our understanding of such interactions in aquatic ecosystems. More broadly, this work contributes to the ongoing debate on the origins of magnetoreception in eukaryotes.

Abstract The African citrus triozid (ACT), Trioza erytreae (Del Guercio, 1918) (Hemiptera: Triozidae), is a significant pest of citrus in southern Africa serving as a vector of African citrus greening disease associated with the phloem-limited gram-negative bacterium “Candidatus Liberibacter africanus” (CLaf). ACT can also vector another Liberibacter species, “Ca. Liberibacter asiaticus” (CLas) associated with Asian citrus greening. Given the confirmed presence of CLas on the African continent, efforts to monitor populations of ACT as well as associated liberibacters in citrus environments have been enhanced since 2021. Trapping and active collections in citrus surroundings indicated the presence of two triozid species with similar morphology to ACT and five other triozids which were morphologically distinct. This study aimed to characterise the diversity of triozid species around citrus and determine their association with liberibacter. Morphological characters and nucleotide sequence phylogeny of the mitochondrial cytochrome c oxidase I (COI) gene region supported the distinction of seven triozid species including ACT. CLaf was only detected in ACT. None of the other triozid species had any liberibacter species associated with them. Our results suggest the presence of other triozid species in other African countries, which probably were misidentified as ACT. Our findings highlight the need for a comprehensive taxonomic revision of triozids associated with citrus. Integrating morphological and molecular characters in a revised classification will be essential for accurate identification of ACT. Molecular confirmation is needed for confidence in distinguishing ACT from closely related non-pest species.

Abstract Segmented filamentous bacteria (SFB) describe morphologically similar gut commensals found in mammals, fish and birds. In mice, SFB intimately colonizes the ileal epithelium at the time of weaning and elicits a strong pleiotropic immune activation that fosters colonization resistance while augmenting disease severity in various disease models. SFB is therefore critical in both health and disease but information regarding SFB in humans remains limited. Here, we first identify and characterize a human SFB species with SFB-specific morphology, including the hook-like tip structure that mediates attachment, and unique genome features, including a starch and glycogen degradation module. This species, which we name Anisomitus miae and establish as the nomenclature type for the SFB genus, is common across Africa. We then bioinformatically identify, based on the 16S rRNA gene V3-V4 variable region sequence, four major, and two minor, human SFB lineages in forty-four countries distributed across all six inhabited continents. We provide evidence towards the co-colonization potential of the SFB lineages and their colonization dynamics, including a potent but short-lived colonization peak in children between one to five years of age. This study establishes the presence of multiple SFB species in the human population and SFB as a minor but wide-spread group of commensals in humans.

ABSTRACT Crape jasmine is a beautiful evergreen flowering shrub and is native to India. During a survey in 2025, severe yellowing symptoms with stunted growth of the plant was observed on the crap jasmine plant at Bhopal, Central India. For the identification of ‘ Candidatus phytoplasma species’ on crap jasmine, symptomatic and asymptomatic leaf samples were collected and total DNA was extracted. The phytoplasma 16S rRNA gene was successfully amplified by direct and nested PCR using isolated DNA and phytoplasma‐specific primers from three symptomatic plants. The amplified ~1.2 kb nested PCR products from three samples were sequenced, and the resulting 16S rRNA gene nucleotide sequences were submitted to GenBank under the accession numbers PX442245, PX890108 and PX890109. Sequence analysis of all three isolates (PX442245, PX890108 and PX890109) revealed the highest nucleotide sequence identity (99%) and close phylogenetic relationships with reference strains of brinjal little leaf phytoplasma, ‘ Candidatus Phytoplasma trifolii’ (16SrVI group), predominantly belonging to the 16SrVI‐D subgroup. In silico RFLP analysis of the 16S rRNA gene sequences of the phytoplasma isolates under study showed the highest similarity to the reference strain of the 16SrVI‐D subgroup, with similarity coefficients ranging from 0.93 to 0.86. To the best of our knowledge, this is the first report of a ‘ Candidatus Phytoplasma trifolii’‐related strain (16SrVI‐D subgroup) associated with yellows disease of crape jasmine ( Tabernaemontana divaricata ) in India.