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Title: Endosymbiotic microbiota of Asian Citrus Psyllid (Diaphorina citri)

Author
item Hert, Mizuri
item Hunter, Wayne
item Dowd, Scot

Submitted to: International Research Conference on Huanglongbing
Publication Type: Proceedings
Publication Acceptance Date: 11/5/2008
Publication Date: 12/1/2008
Citation: Hert, M.M., Hunter, W.B., Dowd, S.E. 2008. Endosymbiotic microbiota of Asian citrus psyllid (Diaphorina citri). 6.6, p. 224-227. In: Proceedings of International Research Conference on Huanglongbing, December 2008. Available: www.plantmanagementnetwork.org.

Interpretive Summary: Eight bacteria species were discovered within the Asian citrus psyllid. The causes of huanglongbing may be induced by more than one microbial agent. Thus, we examined the microbial community in the Asian citrus psyllid (AsCP) (Diaphorina citri, Hemiptera: Psyllidae). Citrus greening is one of the most severe diseases of citrus in Asia and Africa and is caused by an unculturable, gram-negative, phloem-limited bacteria, C. Liberibacter spp., belonging to the a-subdivision of the Proteobacteria. The disease, called citrus greening disease in the U.S., is known as huanglongbing world-wide, and was discovered in Florida during 2005. The disease is transmitted from infected to healthy plants by AsCP. One strategy to manage citrus greening is aimed at suppression of psyllid populations. Insects such as psyllids within the Hemiptera feed from the phloem of plants, ingesting a diet which includes rich carbohydrates but deficient in essential amino acids. These insects support maternally inherited bacterial mutualists, referred to as endosymbionts. The endosymbionts live within specialized host cells known as bacteriocytes and are generally thought to supplement their host’s diet. We analyzed eubacterial 16S-23S rDNA amplified from AsCP and identified transcripts from a cDNA psyllid library made from field collected psyllids feeding on citrus. Sequence comparison to the GenBank database produced evidence of several bacterial species which included: a Syncytium endosymbiont of AsCP (accession number EF433792) and Wolbachia endosymbiont of AsCP (accession number EF433793). The 2.5 kb of PCR product obtained with primer pair 10F, 480R contained six major types of sequences (A-E). The A-type and E-type sequences were members of the beta-Proteobacteria, closely related to Janthinobacterium IC161(99 percent) and Oxalobacteraceae(97-98 percent). The B-type sequence was a member of the gamma-Proteobacteria, closely related to Escherichia(96 percent)and Shigella(95 percent). The C-type sequence was a member of the gamma-Proteobacteria, closely related to Alkanindiges illinoisensis(97 percent). The D-type sequence was a member of the gamma-Proteobacteria, closely related to Acinetobacter sp.(95 percent) and Alvinella pompejana symbiont APG130A(97 percent). Acinetobacter sp. are widespread in nature and can be obtained from water, soil and living organism. Acinetobacter are known to be involved in biodegradation of a number of different compounds. The F-type sequence was a member of the beta-Proteobacteria, closely related to Nitrosospira multiformis (91 percent). Biological functions of the endosymbionts of psyllids have not been investigated. Here we provide a first report of functional bacterial homologies from AsCP microbial data: such as Carbazole degrading bacteria, Janthinobacterium sp. IC161 (99 percent), ammonia-oxidizing bacterium, Nitrosospira multiformis ATCC25196 (CP000103) (91 percent), multidrug resistant bacteria, Acinetobacter baumannii ACICU(CP000863)(95 percent). These data suggest psyllids are supported by several endosymbiotic bacteria and live with a rich bacterial fauna of various types all of which may have important life-supporting functions and/or interactions between each other and Liberibacter asiaticus when it occurs in psyllids.

Technical Abstract: The causes of huanglongbing may be induced by more than one microbial agent. Thus, we examined the microbial community in the Asian citrus psyllid (AsCP) (Diaphorina citri, Hemiptera: Psyllidae). Citrus greening is one of the most severe diseases of citrus in Asia and Africa and is caused by an unculturable, gram-negative, phloem-limited bacteria, C. Liberibacter spp., belonging to the a-subdivision of the Proteobacteria. The disease, called citrus greening disease in the U.S., is known as huanglongbing world-wide, and was discovered in Florida during 2005. The disease is transmitted from infected to healthy plants by AsCP. One strategy to manage citrus greening is aimed at suppression of psyllid populations. Insects such as psyllids within the Hemiptera feed from the phloem of plants, ingesting a diet which includes rich carbohydrates but deficient in essential amino acids. These insects support maternally inherited bacterial mutualists, referred to as endosymbionts. The endosymbionts live within specialized host cells known as bacteriocytes and are generally thought to supplement their host’s diet. We analyzed eubacterial 16S-23S rDNA amplified from AsCP and identified transcripts from a cDNA psyllid library made from field collected psyllids feeding on citrus. Sequence comparison to the GenBank database produced evidence of several bacterial species which included: a Syncytium endosymbiont of AsCP (accession number EF433792) and Wolbachia endosymbiont of AsCP (accession number EF433793). The 2.5 kb of PCR product obtained with primer pair 10F, 480R contained six major types of sequences (A-E). The A-type and E-type sequences were members of the ß-Proteobacteria, closely related to Janthinobacterium IC161(99 percent) and Oxalobacteraceae(97-98 percent). The B-type sequence was a member of the '-Proteobacteria, closely related to Escherichia(96 percent)and Shigella(95 percent). The C-type sequence was a member of the '-Proteobacteria, closely related to Alkanindiges illinoisensis(97 percent). The D-type sequence was a member of the '-Proteobacteria, closely related to Acinetobacter sp.(95 percent) and Alvinella pompejana symbiont APG130A(97 percent). Acinetobacter sp. are widespread in nature and can be obtained from water, soil and living organism. Acinetobacter are known to be involved in biodegradation of a number of different compounds. The F-type sequence was a member of the ß-Proteobacteria, closely related to Nitrosospira multiformis (91 percent). Biological functions of the endosymbionts of psyllids have not been investigated. Here we provide a first report of functional bacterial homologies from AsCP microbial data: such as Carbazole degrading bacteria, Janthinobacterium sp. IC161 (99 percent), ammonia-oxidizing bacterium, Nitrosospira multiformis ATCC25196 (CP000103) (91 percent), multidrug resistant bacteria, Acinetobacter baumannii ACICU(CP000863)(95 percent). These data suggest psyllids are supported by several endosymbiotic bacteria and live with a rich bacterial fauna of various types all of which may have important life-supporting functions and/or interactions between each other and Liberibacter asiaticus when it occurs in psyllids.