Influence of iridoid glycoside containing host plants on midgut β-glucosidase activity in a polyphagous caterpillar, Spilosoma virginica Fabricius (Arctiidae)

The interplay between toxin-releasing β-glucosidase and plant iridoid glycosides impairs larval development in a generalist caterpillar, Grammia incorrupta (Arctiidae)

“…Variation in any of these features may affect the suitability of a plant as food. Plant secondary metabolites are particularly important as they are often crucial in determining insect diet breadth and may be sequestered by the insect or may require metabolic detoxification, either of which can incur physiological costs (Camara, 1997;Pankoke et al, 2010).…”

“…The aglycone's mechanism of toxicity is hypothesized to resemble that of alkylating agents that bind covalently to nucleophilic side chains (e.g., eNH 2 of lysine) via imine formation (Bartholomaeus and Ahokas, 1995;Kim et al, 2000;Konno et al, 1997Konno et al, , 1999. Several studies showed that, after enzymatic hydrolysis, the iridoid aglycones cross-link proteins and also act as enzyme inhibitors (Bartholomaeus and Ahokas, 1995;Konno et al, 1999;Ling et al, 2003;Park et al, 2010). b-Glucosidases are ubiquitous enzymes found in bacteria, fungi, plants and animals. In insects, b-glucosidases are mainly found in the gut where they act as digestive enzymes Ferreira, 1994, 2005).…”

“…As b-glucosidases may release toxic aglycones from digested plant glycosides potentially leading to self-intoxication in the insect, they have become focal enzymes in the study of planteinsect interactions. Several herbivorous insect species have been shown to adaptively decrease their b-glucosidase activity in response to feeding on diets containing toxic glycosides (Desroches et al, 1997;Ferreira et al, 1997;Lindroth, 1988;Pankoke et al, 2010).…”

Performance of secondary parasitoids on chemically defended and undefended hosts

“…In contrast, G. agilis both retained iridoid glycosides as adults and left some in the host cocoon unmetabolized (as meconium), or in the host remains. In order to sequester iridoid glycosides an insect must isolate the ingested compounds from the gut glucosidases and transport them to the hemolymph or other body tissue by an unknown mechanism (Pankoke, Bowers, & Dobler 2010). This mechanism probably comes at a cost (Smilanich et al 2009;Lindstedt et al 2010), but has evolved in many insect lineages (Dobler 2001), and may be adaptive (Harvey et al 2005).…”

Adaptive phenotypic plasticity of gypsy moth digestive enzymes

“…Considerable plasticity of digestive enzyme activity in response to variation in the nutritive and antinutritive characteristics of host plants has also been detected in these insects [12][13][14]. Many plant secondary compounds may bind to plant protein, preventing its digestion, or reduce the activity of digestive enzymes (such as total serine proteinase, trypsin, aminopeptidase [15,16], amylase [17], and glucosidase [18]), or affect enzyme regulation [13], thus hampering food digestion. On the other hand, insects can respond to these challenges through quantitative changes, i.e.…”