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Research Project: IPM Methods for Insect Pests of Orchard Crops

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Title: Annotation of the Asian citrus psyllid genome reveals a reduced innate immune system

Author
item ARP, ALEX - University Of Florida
item Hunter, Wayne
item PELZ-STELINSKI, KIRSTEN - University Of Florida

Submitted to: Frontiers in Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2016
Publication Date: 11/29/2016
Citation: Arp, A.P., Hunter, W.B., Pelz-Stelinski, K. 2016. Annotation of the Asian citrus psyllid genome reveals a reduced innate immune system. Frontiers in Physiology. 7:570.

Interpretive Summary: Citrus production worldwide is currently facing significant losses due to citrus greening disease, also known as huanglongbing. The citrus greening bacteria, Liberibacter asiaticus (Las) is a persistent propagative pathogen transmitted by the Asian citrus psyllid (ACP). Hemipterans characterized to date lack a number of insect immune genes, including those associated with a pathway which targets gram-negative bacteria. The ACP draft genome was used to characterize this insect's immune defense genes. We found that Asian citrus psyllid has a reduced immune capability similar to that observed in some other hemipterans such as aphids and bedbugs. The absence of specific immune genes from the ACP genome may facilitate Las infections, enabling ACP to carry and transmit this pathogen.

Technical Abstract: Citrus production worldwide is currently facing significant losses due to citrus greening disease, also known as huanglongbing. The citrus greening bacteria, Candidatus Liberibacter asiaticus (CLas), is a persistent propagative pathogen transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). Hemipterans characterized to date lack a number of insect immune genes, including those associated with the Imd pathway which targets Gram-negative bacteria. The D. citri DIACI_1.0 genome was used to characterize the immune defense genes present in D. citri. Predicted messenger ribonucleic acids (mRNAs) identified by screening the published D. citri annotated transcriptome were manually searched using a custom database of immune genes from previously annotated insect genomes. Toll and JAK/STAT pathways, general defense genes Dual oxidase, Nitric oxide synthase, prophenoloxidase, and cellular immune defense genes were present in D. citri. In contrast, D. citri lacked genes for the Imd pathway, most antimicrobial peptides, 1,3-ß-glucan recognition proteins (GNBPs), and complete peptidoglycan recognition proteins. These data suggest that D. citri has a reduced immune capability similar to that observed in Arcythosiphon pisum, Pediculus humanus, and Rhodnius prolixus. The absence of immune system genes from the Diaphorina citri genome may facilitate CLas infections, enabling the psyllid to host and transmit the bacterium. The psyllid immune system is possibly compensated for by their microbial endosymbionts.