Aphid biology: Expressed genes from alate Toxoptera citricida the brown citrus aphid

摘要

The brown citrus aphid, Toxoptera citricida (Kirkaldy), is considered the primary vector of citrus tristeza virus, a severe pathogen which causes losses to citrus industries worldwide. The alate (winged) form of this aphid can readily fly long distances with the wind, thus spreading citrus tristeza virus in citrus growing regions. To better understand the biology of the brown citrus aphid and the emergence of genes expressed during wing development, we undertook a large-scale 5′ end sequencing project of cDNA clones from alate aphids. Similar large-scale expressed sequence tag (EST) sequencing projects from other insects have provided a vehicle for answering biological questions relating to development and physiology. Although there is a growing database in GenBank of ESTs from insects, most are from Drosophila melanogaster and Anopheles gambiae, with relatively few specifically derived from aphids. However, important morphogenetic processes are exclusively associated with piercing-sucking insect development and sap feeding insect metabolism. In this paper, we describe the first public data set of ESTs from the brown citrus aphid, T. citricida. The cDNA library was derived from alate adults due to their significance in spreading viruses (e.g., citrus tristeza virus). Over 5180 cDNA clones were sequenced, resulting in 4263 high-quality ESTs. Contig alignment of these ESTs resulted in 2124 total assembled sequences, including both contiguous sequences and singlets. Approximately 33% of the ESTs currently have no significant match in either the non-redundant protein or nucleic acid databases. Sequences returning matches with an E-value of ≤ −10 using BLASTX, BLASTN, or TBLASTX were annotated based on their putative molecular function and biological process using the Gene Ontology classification system. These data will aid research efforts in the identification of important genes within insects, specifically aphids and other sap feeding insects within the Order Hemiptera.The sequence data described in this paper have been submitted to Genbank's dbEST under the following accession numbers.: , , , , , .

>Abbreviation:

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EST

expressed sequence tag

class="kwd-title">Keywords: Aphididae, cDNA, EST, Gene expression, Hemiptera, Development, Toxoptera class="head no_bottom_margin" id="s1title" style="text-transform: uppercase;">IntroductionThe brown citrus aphid, Toxoptera citricida (Kirkaldy), is one of the most devastating pests of citrus, causing extensive crop losses worldwide. Feeding by this aphid alone can cause severe damage to citrus. However, it poses an even greater threat to citrus because of its efficient transmission of citrus tristeza closterovirus ().Since the brown citrus aphid genomic sequence is not available, expressed sequence tags (ESTs) derived from single-pass sequencing of cDNA clones prepared from the brown citrus aphid provide an invaluable resource for the identification of genes associated with the biology of the alate adult life stage. In the past, cloning of genes encoding enzymes of specific biochemical pathways by single-pass sequencing of cDNA clones has been a very successful strategy, particularly when the cDNA libraries have been prepared from tissues with high activity for the respective enzymes (; ; ; ; ). This enables investigators to isolate genes derived from specific tissues and/or life stages for more detailed study, which may include developing efficient biocontrol methods.Additionally, ESTs and their accompanying cDNAs, provide the means to construct glass or nylon based arrays that can be used for transcript profiling on a genome-wide scale (; ; ). A careful bioinformatic analysis identifying life stage-specific ESTs is a prerequisite in order to obtain a comprehensive and representative set of cDNAs for gene expression studies by arrays (). Given that there are only a small number of insect ESTs in public databases it was essential to build a life-stage specific library derived from aphids so that analysis of metabolism and development on a genome-wide scale could be accomplished. Even without subsequent array analysis, a relatively large number of ESTs from a specific life stage can provide clues toward the expression of specific genes important to the functions expressly connected with that life stage (href="#i1536-2442-003-23-0001-rafalski1" rid="i1536-2442-003-23-0001-rafalski1" class=" bibr popnode tag_hotlink tag_tooltip" id="__tag_96701389">Rafalski et al., 1998; href="#i1536-2442-003-23-0001-arbeitman1" rid="i1536-2442-003-23-0001-arbeitman1" class=" bibr popnode tag_hotlink tag_tooltip" id="__tag_96701388">Arbeitman et al., 2002). In most cases and within statistical limitations, the abundance of a specific cDNA in the EST collection is a measure of gene expression (href="#i1536-2442-003-23-0001-audic1" rid="i1536-2442-003-23-0001-audic1" class=" bibr popnode tag_hotlink tag_tooltip" id="__tag_96701384">Audic and Claverie, 1997). This technique, referred to as a “digital or electronic northern”, has been utilized in several similar studies to gauge relative gene expression in various tissues. The data sets are available at GenBank, dbEST under the following accession numbers.: id="__tag_227978695" class="tag_hotlink" href="uccore/?term=CB814527:CB814982[pacc]" ref="uccore/?term=CB814527:CB814982[pacc]">{"type":"entrez-nucleotide-range","attrs":{"text":"CB814527-CB814982","start_term":"CB814527","end_term":"CB814982","start_term_id":"29940382","end_term_id":"29941274"}}CB814527-CB814982, id="__tag_227978701" class="tag_hotlink" href="uccore/?term=CB832665:CB833296[pacc]" ref="uccore/?term=CB832665:CB833296[pacc]">{"type":"entrez-nucleotide-range","attrs":{"text":"CB832665-CB833296","start_term":"CB832665","end_term":"CB833296","start_term_id":"30030912","end_term_id":"30031543"}}CB832665-CB833296, id="__tag_227978706" class="tag_hotlink" href="uccore/?term=CB854878:CB855147[pacc]" ref="uccore/?term=CB854878:CB855147[pacc]">{"type":"entrez-nucleotide-range","attrs":{"text":"CB854878-CB855147","start_term":"CB854878","end_term":"CB855147","start_term_id":"30048924","end_term_id":"30049282"}}CB854878-CB855147, id="__tag_227978704" class="tag_hotlink" href="uccore/?term=CB909714:CB910020[pacc]" ref="uccore/?term=CB909714:CB910020[pacc]">{"type":"entrez-nucleotide-range","attrs":{"text":"CB909714-CB910020","start_term":"CB909714","end_term":"CB910020","start_term_id":"30124375","end_term_id":"30124681"}}CB909714-CB910020, id="__tag_227978699" class="tag_hotlink" href="uccore/?term=CB936196:CB936346[pacc]" ref="uccore/?term=CB936196:CB936346[pacc]">{"type":"entrez-nucleotide-range","attrs":{"text":"CB936196-CB936346","start_term":"CB936196","end_term":"CB936346","start_term_id":"30221676","end_term_id":"30221675"}}CB936196-CB936346, id="__tag_227978700" class="tag_hotlink" href="uccore/?term=CD449954:CD450759[pacc]" ref="uccore/?term=CD449954:CD450759[pacc]">{"type":"entrez-nucleotide-range","attrs":{"text":"CD449954-CD450759","start_term":"CD449954","end_term":"CD450759","start_term_id":"31364688","end_term_id":"31365499"}}CD449954-CD450759.