Annotation of the Asian Citrus Psyllid Genome Reveals a Reduced Innate Immune System.

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, Kuwayama (Hemiptera: Liviidae). Hemipterans characterized to date lack a number of insect immune genes, including those associated with the Imd pathway targeting Gram-negative bacteria. The draft genome was used to characterize the immune defense genes present in . Predicted mRNAs identified by screening the published annotated draft genome 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 . In contrast, lacked genes for the Imd pathway, most antimicrobial peptides, 1,3-β-glucan recognition proteins (GNBPs), and complete peptidoglycan recognition proteins. These data suggest that has a reduced immune capability similar to that observed in , and . The absence of immune system genes from the genome may facilitate Las infections, and is possibly compensated for by their relationship with their microbial endosymbionts.