Expressed sequence tags from the midgut of Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae)

Abstract

The midgut is a key tissue in insect science. Physiological roles include digestion and peritrophic membrane function, as well as being an important target for insecticides. We used an expressed sequence tag (EST) approach to identify candidate genes and gene families involved in these processes in the light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae). Two cDNA libraries were constructed from dissected midgut of third to fifth instar larvae. Clustering analysis of 6416 expressed sequence tags produced 1178 tentative unique genes comprising 725 tentative contigs and 453 singletons. The sequences show similar codon usage to sequences from other lepidopterans, a Kozak consensus sequence similar to Drosophila and single nucleotide polymorphisms (SNPs) were detected at a frequency of 1.35/kb. The identity of the most common Interpro families correlates well with major known functions of the midgut. Phylogenetic analysis was conducted on representative sequences from selected multigene families. Gene families include a broad range of digestive proteases, lipases and carbohydrases that appear to have degradative capacity against the major food components found in leaves, the diet of these larvae; and carboxylesterases, glutathione-S-transferases and cytochrome P450 monooxygenases, potentially involved in xenobiotic degradation. Two of the larger multigene families, serine proteases and lipases, expressed a high proportion of genes that are likely to be catalytically inactive.

Tissue-Specific Transcriptome Profiling of Plutella Xylostella Third Instar Larval Midgut

“…The target site for Bt toxins is believed to be the midgut, a dynamic tissue which plays a vital role in metabolism, digestion, and detoxification. In Lepidoptera, previous studies have focused on the role of proteases, lipases and carbohydrases in digestion, and carboxylesterases, glutathione-s-transferases and cytochrome P450s in xenobiotic metabolism in the midgut 13, 14, 15. With the advent of genomics and its “omics” tools, current research looked more closely at the physiological and toxicological changes at a global level instead of focusing on individual genes in the midgut.…”

Analysis of Expressed Sequence Tags and Characterization of a Novel Gene, Slmg7, in the Midgut of the Common Cutworm, Spodoptera litura

“…EST analysis of midguts has been reported in several insects, such as Bombyx mori [1], Drosophila melanogaster [2], Manduca sexta [3], Chironomus tentans [4], Mamestra configurata [5], Spodoptera frugiperda [6], Epiphyas postvittana [7], Choristoneura fumiferana [8], Anopheles stephensi [9] and Plutella xylostella [10]. However, it is found that there are always certain percentages (ranged from 13% to 30%) of ESTs that show low similarities or no similarity to sequences deposited in the public databases.…”

Immunity or Digestion

“…Bacteria present in the Drosophila gut are thought to release peptidoglycan fragments that bind to specific PGRP (peptidoglycan recognition protein) receptors and induce the imd pathway (13-15). Simpson et al (16) described a sequence (EpGRP1) with similarity to ␤1,3-glucanbinding proteins from Anopheles gambiae and Bombyx mori in ESTs derived from the larval midgut of Epiphyas postvittana. In a proteomic study of the lumen contents of larval midgut of Helicoverpa armigera, we (17) discovered a similar protein that we named GH16betaGRP-1 (glycosyl hydrolase family 16, ␤-glucan recognition protein 1) secreted into the lumen.…”