Article

Expressed sequence tags from the midgut of Epiphyas postvittana (Walker) (Lepidoptera: Torticidae). Insect Mol Biol

Horticulture and Food Research Institute, Palmerston North, New Zealand.
Insect Molecular Biology (Impact Factor: 2.59). 01/2008; 16(6):675-90. DOI: 10.1111/j.1365-2583.2007.00763.x
Source: PubMed

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.

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    • "The diversity and plasticity of proteases expressed in the insect alimentary canal enables them to hydrolyze proteins into short peptides or individual amino acids. Also, these proteases enable insect to defend themselves against a variety of dietary toxins and antinutritional compounds encountered in their host plants (Bown et al., 2004; Prabhakar et al., 2007; Simpson et al., 2007; Ge et al., 2012; Chen et al., 2013; Spit et al., 2014). Cysteine proteases are important and vital enzymes in many invertebrate groups that have different functions including functions in digestion (Goptar et al., 2012), embryogenesis (Hashmi et al., 2002), molting (Liu et al., 2006), tissue remodeling during insect metamorphosis (Wang et al., 2009), detoxification of plant defensive proteins (Koo et al., 2008), and immune responses (Zhang et al., 2013). "
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