spiroplasma citri
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2022 ◽  
Vol 10 (1) ◽  
pp. 183
Author(s):  
Tourya Sagouti ◽  
Zineb Belabess ◽  
Naima Rhallabi ◽  
Essaid Ait Barka ◽  
Abdessalem Tahiri ◽  
...  

Citrus stubborn was initially observed in California in 1915 and was later proven as a graft-transmissible disease in 1942. In the field, diseased citrus trees have compressed and stunted appearances, and yield poor-quality fruits with little market value. The disease is caused by Spiroplasma citri, a phloem-restricted pathogenic mollicute, which belongs to the Spiroplasmataceae family (Mollicutes). S. citri has the largest genome of any Mollicutes investigated, with a genome size of roughly 1780 Kbp. It is a helical, motile mollicute that lacks a cell wall and peptidoglycan. Several quick and sensitive molecular-based and immuno-enzymatic pathogen detection technologies are available. Infected weeds are the primary source of transmission to citrus, with only a minor percentage of transmission from infected citrus to citrus. Several phloem-feeding leafhopper species (Cicadellidae, Hemiptera) support the natural spread of S. citri in a persistent, propagative manner. S. citri-free buds are used in new orchard plantings and bud certification, and indexing initiatives have been launched. Further, a quarantine system for newly introduced types has been implemented to limit citrus stubborn disease (CSD). The present state of knowledge about CSD around the world is summarized in this overview, where recent advances in S. citri detection, characterization, control and eradication were highlighted to prevent or limit disease spread through the adoption of best practices.


2021 ◽  
Author(s):  
Carole Lartigue ◽  
Bastien Lambert ◽  
Fabien Rideau ◽  
Marion Decossas ◽  
Mélanie Hillion ◽  
...  

In bacteria, cell shape is determined and maintained through a complex interplay between the peptidoglycan cell wall and cytoplasmic filaments made of polymerized MreB. Spiroplasma species, members of the Mollicutes class, challenge this general understanding because they are characterized by a helical cell shape and motility without a cell wall. This specificity is thought to rely on five MreB isoforms and a specific fibril protein. In this study, combinations of these five MreBs and of the fibril from Spiroplasma citri were expressed in another Mollicutes, Mycoplasma capricolum. Mycoplasma cells that were initially pleomorphic, mostly spherical, turned into helices when MreBs and fibrils were expressed in this heterologous host. The fibril protein was essential neither for helicity nor for cell movements. The isoform MreB5 had a special role as it was sufficient to confer helicity and motility to the mycoplasma cells. Cryo-electron microscopy confirmed the association of MreBs and fibril-based cytoskeleton with the plasma membrane, suggesting a direct effect on the membrane curvature. Finally, the heterologous expression of these proteins, MreBs and fibril, made it possible to reproduce the kink-like motility of spiroplasmas without providing the ability of cell movement in liquid broth. We suggest that other Spiroplasma components, not yet identified, are required for swimming, a hypothesis that could be evaluated in future studies using the same model.


Author(s):  
Mohammad Salehi ◽  
Mohammad Mehdi Faghihi ◽  
Elham Salehi ◽  
Assunta Bertaccini

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Rachel Rattner ◽  
Shree Prasad Thapa ◽  
Tyler Dang ◽  
Fatima Osman ◽  
Vijayanandraj Selvaraj ◽  
...  

Abstract Background Spiroplasma citri comprises a bacterial complex that cause diseases in citrus, horseradish, carrot, sesame, and also infects a wide array of ornamental and weed species. S. citri is transmitted in a persistent propagative manner by the beet leafhopper, Neoaliturus tenellus in North America and Circulifer haematoceps in the Mediterranean region. Leafhopper transmission and the pathogen’s wide host range serve as drivers of genetic diversity. This diversity was examined in silico by comparing the genome sequences of seven S. citri strains from the United States (BR12, CC-2, C5, C189, LB 319, BLH-13, and BLH-MB) collected from different hosts and times with other publicly available spiroplasmas. Results Phylogenetic analysis using 16S rRNA sequences from 39 spiroplasmas obtained from NCBI database showed that S. citri strains, along with S. kunkelii and S. phoeniceum, two other plant pathogenic spiroplasmas, formed a monophyletic group. To refine genetic relationships among S. citri strains, phylogenetic analyses with 863 core orthologous sequences were performed. Strains that clustered together were: CC-2 and C5; C189 and R8-A2; BR12, BLH-MB, BLH-13 and LB 319. Strain GII3–3X remained in a separate branch. Sequence rearrangements were observed among S. citri strains, predominantly in the center of the chromosome. One to nine plasmids were identified in the seven S. citri strains analyzed in this study. Plasmids were most abundant in strains isolated from the beet leafhopper, followed by strains from carrot, Chinese cabbage, horseradish, and citrus, respectively. All these S. citri strains contained one plasmid with high similarity to plasmid pSci6 from S. citri strain GII3–3X which is known to confer insect transmissibility. Additionally, 17 to 25 prophage-like elements were identified in these genomes, which may promote rearrangements and contribute to repetitive regions. Conclusions The genome of seven S. citri strains were found to contain a single circularized chromosome, ranging from 1.58 Mbp to 1.74 Mbp and 1597–2232 protein-coding genes. These strains possessed a plasmid similar to pSci6 from the GII3–3X strain associated with leafhopper transmission. Prophage sequences found in the S. citri genomes may contribute to the extension of its host range. These findings increase our understanding of S. citri genetic diversity.


2021 ◽  
Author(s):  
Vani Pande ◽  
Nivedita Mitra ◽  
Saket Rahul Bagde ◽  
Ramanujam Srinivasan ◽  
Pananghat Gayathri

MreB, the bacterial ancestor of eukaryotic actin, is responsible for shape in most rod- shaped bacteria. While the eukaryotic actin utilizes ATP hydrolysis to drive filament treadmilling, the relevance of nucleotide-driven polymerization dynamics for MreB function is unclear. Here, we report mechanistic insights into the interplay between nucleotide-binding, ATP hydrolysis and membrane-binding of Spiroplasma citri MreB5 (ScMreB5). Antiparallel double protofilament assembly of ScMreB5WT with ATP, ADP or AMPPNP and an ATPase deficient mutant ScMreB5E134A demonstrate that the filaments assemble independent of ATP hydrolysis. However, capture of the filament dynamics revealed that efficient filament formation, bundling through lateral interactions and filament disassembly are affected in ScMreB5E134A. Hence, the catalytic glutamate (Glu134 in ScMreB5) plays a dual role - it functions as a switch by sensing the ATP-bound state for filament assembly, and by assisting hydrolysis for triggering disassembly. Glu134 mutation also exhibits an allosteric effect on membrane binding, as observed from the reduced liposome binding compared to that of the wild type. Thus, ATP hydrolysis can modulate filament length and bundling, and consequently the orientation of MreB filaments on the cell membrane depending on the curvature. Binding of ScMreB5 with liposomes is mediated by surface charge-based interactions, demonstrating paralog and organism specific features for MreB function. We conclude that the conserved ATP-dependent polymerization and disassembly upon ATP hydrolysis has been repurposed for modulating curvature-dependent organization of filaments on the membrane.


PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0242392
Author(s):  
Yogita Maheshwari ◽  
Vijayanandraj Selvaraj ◽  
Kristine Godfrey ◽  
Subhas Hajeri ◽  
Raymond Yokomi

“Candidatus Liberibacter asiaticus” (CLas) and Spiroplasma citri are phloem-limited bacteria that infect citrus and are transmitted by insect vectors. S. citri causes citrus stubborn disease (CSD) and is vectored by the beet leafhopper in California. CLas is associated with the devastating citrus disease, Huanglongbing (HLB), and is vectored by the Asian citrus psyllid. CLas is a regulatory pathogen spreading in citrus on residential properties in southern California and is an imminent threat to spread to commercial citrus plantings. CSD is endemic in California and has symptoms in citrus that can be easily confused with HLB. Therefore, the objective of this study was to develop a multiplex qPCR and duplex droplet digital PCR (ddPCR) assay for simultaneous detection of CLas and S. citri to be used where both pathogens can co-exist. The multiplex qPCR assay was designed to detect multicopy genes of CLas—RNR (5 copies) and S. citri–SPV1 ORF1 (13 copies), respectively, and citrus cytochrome oxidase (COX) as internal positive control. Absolute quantitation of these pathogens was achieved by duplex ddPCR as a supplement for marginal qPCR results. Duplex ddPCR allowed higher sensitivity than qPCR for detection of CLas and S. citri. ddPCR showed higher tolerance to inhibitors and yielded highly reproducible results. The multiplex qPCR assay has the benefit of testing both pathogens at reduced cost and can serve to augment the official regulatory protocol for CLas detection in California. Moreover, the ddPCR provided unambiguous absolute detection of CLas and S. citri at very low concentrations without any standards for pathogen titer.


2020 ◽  
Author(s):  
Rachel Rattner ◽  
Shree Prasad Thapa ◽  
Tyler Dang ◽  
Fatima Osman ◽  
Vijayanandraj Selvaraj ◽  
...  

Abstract Background Spiroplasma citri comprises a complex of bacteria that cause diseases in citrus, horseradish, carrot, sesame, and also infect a wide array of ornamental and weed species. S. citri is transmitted in a persistent propagative manner by the beet leafhopper, Neoaliturus tenellus in North America and Circulifer haematoceps in the Mediterranean region. Leafhopper transmission and the pathogen’s wide host range serve as drivers of genetic diversity. This diversity was examined by comparing the genome sequences of seven S. citri strains from the United States (BR12, CC2, C5, C189, LB319, BLH-13, and BLH-MB) collected from different hosts and times with other publicly available spiroplasmas.Results Phylogenetic analysis using 16S rRNA sequences from 39 spiroplasmas obtained from NCBI database showed that S. citri strains, along with S. kunkelii and S. phoeniceum, two other plant pathogenic spiroplasmas, formed a monophyletic group. To refine genetic relationships among S. citri strains, phylogenetic analyses with 863 core orthologous sequences were performed. Strains that clustered together were: CC-12 and C5; C189 and R8-A2; BR12, BLH-MB, BLH13 and LB 319. Strain GII3-3 remained in a separate branch. Sequence rearrangements were observed among S. citri strains, predominantly in the center of the chromosome. One to nine plasmids were identified in the seven S. citri strains analyzed in this study. Plasmids were most abundant in strains isolated from the beet leafhopper, followed by strains from carrot, Chinese cabbage, horseradish and citrus, respectively. All these S. citri strains contained one plasmid with high similarity to plasmid pSci6 from S. citri strain GII3-3X which is known to confer insect transmissibility. Additionally, 17 to 25 prophage-like elements were identified in these genomes, which may promote rearrangements and contribute to repetitive regions. Conclusions The genome of seven S. citri strains were found to contain a single circularized chromosome, ranging from 1.58 Mbp to 1.74 Mbp and 1,597-2,232 protein-coding genes. These strains possessed a plasmid similar to pSci6 from the GII3-3X strain associated with leafhopper transmission. Prophage sequences found in the S. citri genomes may contribute to the extension of its host range. These findings increase our understanding of S. citri genetic diversity.


2020 ◽  
Author(s):  
Yogita Maheshwari ◽  
Vijayanandraj Selvaraj ◽  
Kristine Godfrey ◽  
Subhas Hajeri ◽  
Raymond Yokomi

Abstract“Candidatus Liberibacter asiaticus” (CLas) and Spiroplasma citri are phloem-limited bacteria that infect citrus and are transmitted by insect vectors. S. citri causes citrus stubborn disease (CSD) and is vectored by the beet leafhopper in California. CLas is associated with the devastating citrus disease, Huanglongbing (HLB), and is vectored by the Asian citrus psyllid. CLas is a regulatory pathogen spreading in citrus on residential properties in southern California and is an imminent threat to spread to commercial citrus plantings. CSD is endemic in California and has symptoms in citrus that can be easily confused with HLB. Consequently, a multiplex qPCR and duplex droplet digital PCR (ddPCR) were developed for simultaneous detection of CLas and S. citri. The multiplex qPCR assay was designed to detect multicopy genes of CLas - RNR (5 copies) and S. citri – SPV1 ORF1 (13 copies), respectively, and citrus cytochrome oxidase (COX) as internal positive control. Absolute quantitation of these pathogens was achieved by duplex ddPCR as a supplement for marginal qPCR results. Duplex ddPCR allowed higher sensitivity than qPCR for detection of CLas and S. citri. ddPCR showed higher resilience to inhibitors and yielded highly reproducible results. The multiplex qPCR assay has the benefit of testing both pathogens at reduced cost and can serve to augment the official regulatory protocol for CLas detection in California. Moreover, the ddPCR provided unambiguous absolute detection of CLas and S. citri at very low concentrations without any standards for pathogen titer.


2020 ◽  
Author(s):  
Rachel Rattner ◽  
Shree Prasad Thapa ◽  
Tyler Dang ◽  
Fatima Osman ◽  
Vijayanandraj Selvaraj ◽  
...  

Abstract Background Spiroplasma citri comprises a complex of bacteria that cause diseases in citrus, horseradish, carrot, sesame, and also infect a wide array of ornamental and weed species. S. citri is transmitted in a persistent propagative manner by the beet leafhopper, Neoaliturus tenellus in North America and Circulifer haematoceps in the Mediterranean region. Leafhopper transmission and the pathogen’s wide host range serve as drivers of genetic diversity. This diversity was examined by comparing the genome sequences of seven S. citri strains from the United States (BR12, CC2, C5, C189, LB319, BLH-13, and BLH-MB) collected from different hosts and times with other publicly available spiroplasmas.Results Phylogenetic analysis using 16S rRNA sequences from 39 spiroplasmas obtained from NCBI database showed that S. citri strains, along with S. kunkelii and S. phoeniceum, two other plant pathogenic spiroplasmas, formed a monophyletic group. To refine genetic relationships among S. citri strains, phylogenetic analyses with 863 core orthologous sequences were performed. Strains that clustered together were: CC-12 and C5; C189 and R8-A2; BR12, BLH-MB, BLH13 and LB 319. Strain GII3-3 remained in a separate branch. Sequence rearrangements were observed among S. citri strains, predominantly in the center of the chromosome. One to nine plasmids were identified in the seven S. citri strains analyzed in this study. Plasmids were most abundant in strains isolated from the beet leafhopper, followed by strains from carrot, Chinese cabbage, horseradish and citrus, respectively. All these S. citri strains contained one plasmid with high similarity to plasmid pSci6 from S. citri strain GII3-3X which is known to confer insect transmissibility. Additionally, 17 to 25 prophage-like elements were identified in these genomes, which may promote rearrangements and contribute to repetitive regions. Conclusions The genome of seven S. citri strains were found to contain a single circularized chromosome, ranging from 1.58 Mbp to 1.74 Mbp and 1,597-2,232 protein-coding genes. These strains possessed a plasmid similar to pSci6 from the GII3-3X strain associated with leafhopper transmission. Prophage sequences found in the S. citri genomes may contribute to the extension of its host range. These findings increase our understanding of S. citri genetic diversity.


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