Biology:Liberibacter

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Liberibacter is a genus of Gram-negative bacteria in the Rhizobiaceae family. Detection of the liberibacteria is based on PCR amplification of their 16S rRNA gene with specific primers. Members of the genus are plant pathogens mostly transmitted by psyllids. The genus was originally spelled Liberobacter.[1]

Most importantly, Liberibacter is a causative agent of Huanglongbing disease (HLB) also known as citrus greening disease.[2] Liberibacter is transmitted by two insects from Psyllidae family – Diaphorina citri in Asia, Brazil and Florida, and Trioza erytreae in Africa. The Asian HLB strain, "Candidatus Liberibacter asiaticus" is more heat tolerant, while the African strain, Candidatus Liberibacter africanus is asymptomatic at temperatures above 30 °C.[2] Species of Liberibacter, infecting solanaceous plants has been identified and it was carried by another psyllid, a potato pest Bactericera cockerelli.[2][3]

Genomes

The genetic diversity within the genus is best expressed as the diversity across genomes. More than 60 genomes have been sequenced, ranging in size from 233 kb to about 1.5 MB, hence the genomes are small compared to most other bacteria. The smallest genome (Candidatus Liberibacter asiaticus strain SGCA1) encodes only 655 proteins, while the largest genome (Candidatus Liberibacter asiaticus Tabriz. 3) encodes 2174 proteins.[4][5]

The small genome size is typical for pathogenic bacteria which often undergo genome reduction. This is due to adaptation to their host which often provides many nutrients, so that the parasite does not need genes to produce those nutrients itself.[6]

Pathogenicity

Liberibacter bacteria are carried in the hemolymph and salivary glands of psyllids. Since psyllids feed on sap, this provides bacteria the entry to phloem of the plant.[2] They induce significant metabolic and regulatory changes that damage the plants transport system and affects plants defense systems. These impairments have downstream negative effects on citrus microbiome of the infected plants.[7]

Since pathological Liberibacter cannot be cultivated outside of its vector or host, genetics, bacteria-vector and bacteria-plant interaction have not yet been thoroughly explored. Factors important for adaption and colonization or possible coevolution are not yet understood.[2][7] Only in 2014 the accidental discovery of Liberibacter crescens in Babaco papaya (during a Papaya Bunchy Top Disease study), which can be cultured axenically,[8] allowed researchers to establish the genus and provided a valuable model organism to study related HLB strains.

Liberibacter activates salicylic acid pathway in host, likely due to recognition of extracellular molecules such as lipopolyscacharides or flagella. Pathogen in turn likely mitigates the effects, because it encodes SA hydroxylase, that degrades salicylic acid. Liberibacteria were shown to affect the spread of vector, by influencing the flight frequencies and sexual attraction of D. citri. On the other hand, infection with Liberibacter causes higher mortality of D. citri adults, but not nymphs.[7] Liberibacter is a part of the psyllid microbiota and co-existence with other bacteria likely has impact on the overall fitness of the insect, as well as outcome of the disease.[7]

Treatment

Primary strategy for HLB disease management is a vector control. Antimicrobial treatment can suppress Liberibacter species,[9] however usage of broad spectrum antibiotics is inadvisable due to adverse environmental effects. Alternative treatments, such as heat therapy, i.e., incubation of plant at temperatures above 40 °C for several days, show varying effects. Another suggested alternatives include the use of compounds that alleviate disease symptoms and boost plants defense systems[10] or reinforcing natural citrus microbiota in order to compete with Liberibacter species.[11] Early detection of HLB positive trees and removal from the groves, and extensive control of psyllids are the crucial HLB management strategies.[12][13]

Species

Named species include:[14]

  • "Ca. Liberibacter africanus" corrig. Jagoueix et al. 1994 originated in Africa and is a causal agent of citrus greening disease, also known as huanglongbing, and vectored by the African citrus psyllid Trioza erytreae.[15]
  • "Ca. Liberibacter americanus" Teixeira et al. 2005 is a novel species from Brazil described in 2005 and associated with huanglongbing and vectored by the Asian citrus psyllid Diaphorina citri.[16]
  • "Ca. Liberibacter asiaticus" corrig. Jagoueix et al. 1994 originated in Asia and is a causal agent of huanglongbing, vectored by the Asian citrus psyllid D. citri.[17]
  • "Ca. Liberibacter brunswickensis" Morris et al. 2017[18] associated with the psyllid Acizzia solanicola on eggplant in Australia.
  • Liberibacter crescens Fagen et al. 2014[8] was isolated from papaya growing in Puerto Rico.
  • "Ca. Liberibacter europaeus" Raddadi et al. 2011 is a novel species described in 2010, found in pear trees, where it seems to cause no symptoms and is vectored by the psyllid, Cacopsylla pyri.[19]
  • "Ca. Liberibacter solanacearum" Liefting et al. 2009[20] is a causal agent of zebra chip disease in potatoes. It can also infect other economically important crops including tomatoes, carrot, parsely, parsnip, celery and chervil. There are at least ten haplotypes described within this species, designated LsoA, LsoB, LsoC, LsoD, LsoE, Lso F, LsoG, LsoH, LsoH(Con) and LsoU.[21][22][23] Haplotypes A, B and F are associated with solanaceous plants (potatoes and tomato) and vectored by the potato tomato psyllid Bactericera cockerelli.[24] Haplotypes C, D, E and H affect apiaceous crops (carrots, celery etc.). Haplotypes D and E are vectored by Bactericera trigonica. Haplotype C is vectored by Trioza apicalis. The vector for haplotype H is currently unknown. Haplotype U has been found in Urtica dioica (stinging nettle) and is vectored byTrioza urticae.[23]
    • LsoA is also described as a species as "Ca. Liberibacter psyllidaureus" corrig. Hansen et al. 2008[3] or the misspelling Ca. L. psyllaurous. It is now considered synonymous as the 16S rRNA genes are identical.[25] In addition to being a plant pathogen, LsoA also serves as an endosymbiont for the insect vector, by modifying tomato defenses in favor of itself and its vector.[26]
  • "Ca. Liberibacter ctenarytainae" Thompson et al. 2017 is vectored by Ctenarytaina fuchsiae.[27] Its genome was announced under a different spelling, "Ca. Liberibacter ctenarytaina".[28]
  • "Ca. Liberibacter capsica" Kwak et al. 2021 is vectoed by Russelliana capsici.[29]

References

  1. ↑ "Taxonomy browser 34019". https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?lvl=0&id=34019. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 "Insects as alternative hosts for phytopathogenic bacteria". FEMS Microbiology Reviews 35 (3): 555–75. May 2011. doi:10.1111/j.1574-6976.2011.00264.x. PMID 21251027. 
  3. ↑ 3.0 3.1 "A new Huanglongbing Species, "Candidatus Liberibacter psyllaurous," found to infect tomato and potato, is vectored by the psyllid Bactericera cockerelli (Sulc)". Applied and Environmental Microbiology 74 (18): 5862–5. September 2008. doi:10.1128/AEM.01268-08. PMID 18676707. Bibcode: 2008ApEnM..74.5862H. 
  4. ↑ "Genome List". https://www.bv-brc.org/view/GenomeList/?eq(genome_id,*)&genome()#view_tab=genomes&filter=and(eq(genus,liberibacter),keyword(liberibacter)). 
  5. ↑ "MAG: Candidatus Liberibacter asiaticus isolate Tabriz.3, whole genome shotgun sequencing project" (in en-US). 2022-02-19. https://www.ncbi.nlm.nih.gov/nuccore/JAKQYA000000000.1. 
  6. ↑ Koskiniemi, Sanna; Sun, Song; Berg, Otto G.; Andersson, Dan I. (June 2012). "Selection-driven gene loss in bacteria". PLOS Genetics 8 (6). doi:10.1371/journal.pgen.1002787. ISSN 1553-7404. PMID 22761588. 
  7. ↑ 7.0 7.1 7.2 7.3 "Tale of the Huanglongbing Disease Pyramid in the Context of the Citrus Microbiome". Phytopathology 107 (4): 380–387. April 2017. doi:10.1094/PHYTO-12-16-0426-RVW. PMID 28095208. Bibcode: 2017PhPat.107..380W. 
  8. ↑ 8.0 8.1 Fagen, Jennie R.; Leonard, Michael T.; Coyle, Janelle F.; McCullough, Connor M.; Davis-Richardson, Austin G.; Davis, Michael J.; Triplett, Eric W. (2014). "Liberibactercrescens gen. nov., sp. nov., the first cultured member of the genus Liberibacter". International Journal of Systematic and Evolutionary Microbiology 64 (Pt_7): 2461–2466. doi:10.1099/ijs.0.063255-0. ISSN 1466-5034. PMID 24786353. https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.063255-0. 
  9. ↑ Johnson, E. G. (February 29, 2020). "Zinkicide A Nanotherapeutic for HLB - University of Florida". https://portal.nifa.usda.gov/web/crisprojectpages/1005557-zinkicide-a-nanotherapeutic-for-hlb.html. 
  10. ↑ Alferez, Fernando; Vincent, Christopher; Vashisth, Tripti (June 19, 2019). "Update on Brassinosteroids for HLB Management". Citrus Industry Magazine (Newberry, Florida: AgNet Media). http://citrusindustry.net/2019/06/19/update-on-brassinosteroids-for-hlb-management/. 
  11. ↑ "Challenges for Managing "Candidatus Liberibacter" spp. (Huanglongbing Disease Pathogen): Current Control Measures and Future Directions". Phytopathology 108 (4): 424–435. April 2018. doi:10.1094/PHYTO-07-17-0260-RVW. PMID 28990481. Bibcode: 2018PhPat.108..424B. 
  12. ↑ Pandey, Sheo Shankar; Wang, Nian (June 2019). "Targeted Early Detection of Citrus Huanglongbing Causal Agent ' Candidatus Liberibacter asiaticus' Before Symptom Expression". Phytopathology 109 (6): 952–959. doi:10.1094/PHYTO-11-18-0432-R. PMID 30667340. Bibcode: 2019PhPat.109..952P. 
  13. ↑ Wang, Nian (May 2019). "The Citrus Huanglongbing Crisis and Potential Solutions". Molecular Plant 12 (5): 607–609. doi:10.1016/j.molp.2019.03.008. PMID 30947021. Bibcode: 2019MPlan..12..607W. 
  14. ↑ "Liberibacter". UniProt Consortium. https://www.uniprot.org/taxonomy/34019. 
  15. ↑ "Trioza erytreae". European and Mediterranean Plant Protection Organization (EPPO) quarantine pest. http://www.eppo.org/QUARANTINE/insects/Trioza_erytreae/TRIZER_ds.pdf. 
  16. ↑ ""Ca. Liberibacter americanus", associated with citrus huanglongbing (greening disease) in São Paulo State, Brazil". International Journal of Systematic and Evolutionary Microbiology 55 (5): 1857–62. September 2005. doi:10.1099/ijs.0.63677-0. PMID 16166678. 
  17. ↑ "Asian citrus psyllid". Featured Creatures. http://entomology.ifas.ufl.edu/creatures/citrus/acpsyllid.htm. 
  18. ↑ "Novel "Ca. Liberibacter" species identified in the Australian eggplant psyllid, Acizzia solanicola". Microbial Biotechnology 10 (4): 833–844. July 2017. doi:10.1111/1751-7915.12707. PMID 28387006. 
  19. ↑ ""Ca. Liberibacter europaeus" sp. nov. that is associated with and transmitted by the psyllid Cacopsylla pyri apparently behaves as an endophyte rather than a pathogen". Environmental Microbiology 13 (2): 414–26. February 2011. doi:10.1111/j.1462-2920.2010.02347.x. PMID 21040355. 
  20. ↑ "'Candidatus Liberibacter solanacearum', associated with plants in the family Solanaceae". International Journal of Systematic and Evolutionary Microbiology 59 (Pt 9): 2274–6. September 2009. doi:10.1099/ijs.0.007377-0. PMID 19620372. 
  21. ↑ "A new haplotype of "Ca. Liberibacter solanacearum" identified in the Mediterranean region". European Journal of Plant Pathology 135 (4): 633–639. 2012. doi:10.1007/s10658-012-0121-3. 
  22. ↑ "Association of "Ca. Liberibacter solanacearum" with a vegetative disorder of celery in Spain and development of a real-time PCR method for its detection". Phytopathology 104 (8): 804–11. August 2014. doi:10.1094/PHYTO-07-13-0182-R. PMID 24502203. 
  23. ↑ 23.0 23.1 Sumner-Kalkun, Jason C.; Highet, Fiona; Arnsdorf, Yvonne M.; Back, Emma; Carnegie, Mairi; Madden, Siobhán; Carboni, Silvia; Billaud, William et al. (2020-10-06). "'Candidatus Liberibacter solanacearum' distribution and diversity in Scotland and the characterisation of novel haplotypes from Craspedolepta spp. (Psylloidea: Aphalaridae)" (in en). Scientific Reports 10 (1): 16567. doi:10.1038/s41598-020-73382-9. ISSN 2045-2322. PMID 33024134. Bibcode: 2020NatSR..1016567S. 
  24. ↑ Crosslin, James M.; Munyaneza, Joseph E. (2009). "Evidence that the Zebra Chip Disease and the Putative Causal Agent Can be Maintained in Potatoes by Grafting and in Vitro". American Journal of Potato Research 86 (3): 183–187. doi:10.1007/s12230-009-9070-6. 
  25. ↑ "Haplotypes of "Ca. Liberibacter solanacearum" suggest long-standing separation". European Journal of Plant Pathology 130: 5–12. 2011. doi:10.1007/s10658-010-9737-3. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2318&context=usdaarsfacpub. 
  26. ↑ "Manipulation of plant defense responses by the tomato psyllid (Bactericerca cockerelli) and its associated endosymbiont "Ca. Liberibacter psyllaurous"". PLOS ONE 7 (4). 2012. doi:10.1371/journal.pone.0035191. PMID 22539959. Bibcode: 2012PLoSO...735191C. 
  27. ↑ Thompson, S., Jorgensen, N., Bulman, S., & Smith, G. A novel Candidatus Liberibacter species associated with Ctenarytaina fuchsiae, the New Zealand native fuchsia psyllid. In Science Protecting Plant Health 4187 (Brisbane; 2017).
  28. ↑ "Initial analysis of the draft genome of Candidatus Liberibacter ctenarytaina". THE 13 TH AUSTRALASIAN PLANT VIROLOGY WORKSHOP. February 2018. https://www.researchgate.net/publication/325251517. 
  29. ↑ Kwak, Younghwan; Sun, Penglin; Meduri, Venkata RamaSravani; Percy, Diana M.; Mauck, Kerry E.; Hansen, Allison K. (29 September 2021). "Uncovering Symbionts Across the Psyllid Tree of Life and the Discovery of a New Liberibacter Species, "Candidatus" Liberibacter capsica". Frontiers in Microbiology 12. doi:10.3389/fmicb.2021.739763. 

Further reading

Wikidata ☰ Q4262259 entry



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