Psyllid biology: expressed genes in adult Asian citrus psyllids, Diaphorina citri

Authors: Hunter, Wayne; Dowd, Scot; KATSAR, CATHERINE - APHIS; Shatters, Robert - Bob; McKenzie, Cindy; Hall, David

Submitted to: The Open Entomology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2009
Publication Date: 3/30/2009
Citation: Hunter, W.B., Dowd, S.E., Katsar, C., Shatters, Jr., R.G., McKenzie, C.L., Hall, D.G. 2009. Psyllid biology: Expressed genes in adult Asian citrus psyllids, Diaphorina citri. The Open Entomology Journal. 3:18-29.

Interpretive Summary: In this project, we create and describe the first genetic data set from the Asian citrus psyllid, AsCP, Diaphorina citri. The identification of these genes and proteins advances the field in understanding of the genetic basis of insect growth, development, and disease. The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is a small insect that feeds on the sap of citrus trees and is considered the primary vector of the plant pathogenic bacterium, Candidatus Liberibacter, which causes Huanglongbing, HLB, also known as ‘Citrus Greening’ due to the discoloration of fruit. The bacterium causes severe economic losses to citrus industries worldwide. To better understand the role of psyllid biology and particularly to identify genes which function in: feeding, disease transmission, and the development of insecticide resistance, we undertook a large-scale 5' end sequencing project of cDNA clones from adult psyllids. Similar large-scale expressed sequence tag (EST) sequencing projects from other insects have provided the vehicle for answering these important biological questions. As more genomic information is added to the public database, GenBank, on insects, researchers are beginning to understand the genetic basis of insect growth, development, and disease. Relatively few genes have been specifically isolated from psyllids. In this project, we create and describe the first data set of ESTs from the Asian citrus psyllid. Over 5,906 cDNA clones were sequenced, resulting in 4,445 high-quality AsCP sequences. Sequence alignment resulted in 2,123 total assembled sequences, including both contiguous sequences and singlets. All the sequences were annotated by comparison to all known sequences in the public database at NCBI using computer comparison software BLASTX, TBLASTX, and BLASTN, GenBank, nr ESTdb. The subsequent unigene set produced 517 sequences which had significant identities with homologous genes in the GenBank’s database. The remaining 63% of the sequences showed ‘no significant match’ in either the non-redundant protein or nucleic acid databases, demonstrating that large scale sequencing project such as this still provides valuable new information to the scientific community. The AsCP gene expression data set advances current research efforts in the identification and understanding of psyllid biology, and adds to the growing database of information on insects of economic importance. Identification and characterization of these genes and proteins will provide molecular products and tools which will enable functional genomic studies for the development of new management strategies against psyllids and other insect pests.

Technical Abstract: These results advance the field of psyllid research by identifying genes and their proteins which function in: physiology, feeding, disease transmission, and the development of insecticide resistance. This was accomplished by using the molecular approach of a large-scale 5' end sequencing project of cDNA clones from adult psyllids. The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is considered the primary vector of plant pathogenic bacterium, Candidatus Liberibacter, which causes Huanglongbing, HLB, also known as ‘Citrus greening’, which causes severe economic losses to citrus industries worldwide. Similar large-scale expressed sequence tag (EST) sequencing projects from other insects have provided the vehicle for answering these important biological questions. As more studies like these are completed they add valuable information for comparative studies with other insects. The growing database in GenBank provides genomic information from other insects, most of the available gene sequences are from the dipterans, Drosophila species and Anopheles gambiae; the lepidopteran - Bombyx mori; the hymenopteran Apis mellifera; and the coleopteran Tribolium castaneum. Relatively few genes have been specifically isolated from psyllids. In this paper, we describe the first publicly available data set of ESTs from the psyllid D. citri. Over 5,906 cDNA clones were sequenced, resulting in 4,445 high-quality D. citri ESTs. Sequence alignment of the cDNAs resulted in 2,123 total assembled sequences, including both contiguous sequences and singlets. The putative protein transcript of each assembled sequence was annotated based on the biochemical function of matching gene sequences using BLASTX, TBLASTX, and BLASTN analyses, GenBank, nr ESTdb. The subsequent unigene set produced 517 sequences which had significant identities with homologous genes in the GenBank’s database. The remaining 63% of the cDNA’s showed ‘no significant match’ in either the non-redundant protein or nucleic acid databases, demonstrating that de novo EST sequencing projects can still provide new information to the scientific community. The D. citri gene expression data set advances current research efforts in the identification of genes and physiological processes of psyllids, and adds to the information of genomic data for comparisons with other insect species of economic importance. The identification and characterization of these products: genes and proteins enable functional genomic studies for the development of new tools, probes, and management strategies against psyllids and other hemipterans.