Hemipterans include some of the most important insect pests of agricultural systems and vectors of plant pathogens. The vector, Diaphorina citri (Asian citrus psyllid) belonging to the Psylloidae superfamily, is the primary target of approaches to stop the spread of the pathogen Ca. Liberibacter asiaticus that causes Huanglongbing or citrus greening disease. High quality genomic resources enable rapid functional discovery that can target disease transmission and control. The previous psyllid genome (Diaci v1.1) available in NCBI is missing 25% of the single copy markers conserved in other Hemipterans. Manual genome curation helped to identify a significant number of genome anomalies including misassemblies and missing genes. We present an improved and highly contiguous de novo assembly based on PacBio long reads followed by Dovetail Chicago and Hi-C based scaffolding. The current assembly (Diaci v3) has 13 chromosomal length scaffolds with a genome size of 475 Mb. This is the first report of a chromosomal length assembly in the Hemiptera order according to our knowledge. Full-length cDNA transcripts were sequenced with PacBio Iso-Seq technology from diseased and healthy tissue at multiple life stages. Iso-Seq along with diverse Illumina RNA-Seq expression data were used to predict 19,049 protein-coding genes in psyllid using MAKER annotation pipeline. We also generated a genome independent transcriptome with a comprehensive catalog of all genes in the psyllid.

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The Asian citrus psyllid, Diaphorina citri, is an insect vector that transmits Candidatus Liberibacter asiaticus, the causal agent of the Huanglongbing (HLB), or citrus greening disease. This disease has devastated Florida’s citrus industry, and threatens California’s industry as well as other citrus producing regions around the world. To find novel solutions to the disease, a better understanding of the vector is needed. The D. citri genome has been used to identify and characterize genes involved in Wnt signaling pathways. Wnt signaling is utilized for many important biological processes in metazoans, such as patterning and tissue generation. Curation based on RNA sequencing data and sequence homology confirms 24 Wnt signaling genes within the D. citri genome, including homologs for beta-catenin, Frizzled receptors, and seven Wnt-ligands. Through phylogenetic analysis, we classify D. citri Wnt ligands as Wg/Wnt1, Wnt5, Wnt6, Wnt7, Wnt10, Wnt11, and WntA. The D. citri version 3.0 genome with chromosomal length scaffolds reveals a conserved Wnt1-Wnt6-Wnt10 gene cluster with a gene configuration like that in Drosophila melanogaster. These findings provide greater insight into the evolutionary history of D. citri and Wnt signaling in this important hemipteran vector. Manual annotation was essential for identifying high quality gene models. These gene models can be used to develop molecular systems, such as CRISPR and RNAi, which target and control psyllid populations to manage the spread of HLB. Manual annotation of Wnt signaling pathways was done as part of a collaborative community annotation project.

Diaphorina citri is the insect vector of Huanglongbing (HLB), a disease that has devastated global citrus production. In an effort to better understand the insects biology, the D. citri genome has been manually annotated. Here, we report on D. citri genes involved in both canonical and noncanonical Wnt signaling. In metazoans, Wnt signaling is important for many biological processes such as patterning, cell polarity, tissue generation, and stem cell maintenance. We have curated a complete repertoire of Wnt signaling genes in D. citri. In total, 24 genes associated with canonical and noncanonical Wnt signaling have been annotated including seven Wnt ligands, three frizzled homologs, arrow, and several receptor tyrosine kinases such as ROR and doughnut. We were unable to find Wnt8/D, Wnt9, and Wnt16 along with the various ligand genes that have been lost to insects such as Wnt2-4. The mechanisms of canonical Wnt signaling appear to be mostly conserved and comparable to that found in the model organism, Drosophila melanogaster.

The circadian rhythm is a process involving multiple genes that generates an internal molecular clock, allowing organisms to anticipate environmental conditions produced by the earth's rotation on its axis. This report presents the results of the manual curation of twenty-seven genes likely associated with circadian rhythm in the genome of Diaphorina citri, the Asian citrus psyllid. This insect acts as the vector of the bacterial pathogen Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus greening disease (Huanglongbing). This disease is the most severe detriment to citrus industries and has drastically decreased crop yields worldwide. Based on the genes identified in the psyllid genome, namely cry1 and cry2, D. citri likely possesses a circadian model similar to that of the lepidopteran butterfly, Danaus plexippus. Manual annotation of these genes will allow future molecular therapeutics to be developed that can disrupt the psyllid biology.