![]() These studies have shown a differential genetic response of insects after host plant switches, or the transcriptional response of feeding on specific host plants. More recently, plants are incorporated into molecular studies on the transcriptional response of insects, mimicking a more natural system. Įmpirical evidence for the role of genes involved in the detoxifying ability of insects is mainly based on experimental studies using pesticide and isolated toxin treatments (e.g. Indeed, expansions of detoxification and digestion related gene families have been observed in multiple polyphagous arthropod species, such as the spider mite ( Tetranychus urticae), known to feed on over 1000 different host plant species, the tobacco cutworm ( Spodoptera litura), the fall armyworm ( Spodoptera frugiperda) or the whitefly ( Bemisia tabaci). The evolution of polyphagy is hypothesized to be associated with expansions of gene families involved in host plant use, due to gene duplication and neofunctionalisation, (e.g. showed major expansions of gene families involved in detoxification and digestion including P450s, GSTs and CCEs when comparing two polyphagous moth species to two monophagous species. A recent comparative genomic study by Pearce et al. The ability of an herbivorous insect to feed on a broad host range largely depends on the flexibility and diversity of the insect’s digestion and detoxification system. The metabolized product is conjugated by phase II enzymes such as UDP-glycosyltransferases (UGTs) and glutathione-S-transferases (GSTs), and transported out of the cell by transporters like ATP-binding cassettes (ABCs) and solute carrier proteins (SLC) in phase III. In phase I of the detoxification process, cytochrome P450 monooxygenases (P450s) and carboxyl/choline esterases (CCEs) metabolize toxins. In herbivorous insects the detoxification of plant defence compounds follow a three phased pathway involving members of several known enzyme families. This success is partly dependent on nutrient content and plant defence resistance and is reflected by growth- and developmental rate of the insect. The ability of an herbivorous insect to feed on different host plants does not imply equal herbivore success on each of these plants. ![]() Numerous herbivorous insects have evolved the ability to feed on a large range of host plant species (polyphagy), thereby encountering a variety of plant-specific defence compounds. The 400 million years of interaction and co-evolution between plants and insects has led to a wide diversity of plant defences, to which herbivorous insects in turn have evolved a diverse array of resistance and detoxification mechanisms. This observation leads to the conclusion that a polyphagous herbivore is able to feed on a large variation of host plants due to the flexibility and diversity of genes involved in digestion and detoxification that are deployed in response to particular host plant species. tabacum, with low herbivore success, imply a host plant-specific gene activity for larvae feeding on host plants with suboptimal herbivore success. Whereas the finding of specific gene clusters containing particular digestion and detoxifying genes expressed in larvae feeding on B. mays and the artificial diet suggest a general and non-specific gene activity for host plants with optimal herbivore success. The lack of a host plant-specific gene activity for larvae feeding on Z. exigua larvae deploy particular host plant-specific genes for digestion and detoxification. Functional annotation of these clusters indicates that S. In contrast, for larvae feeding on hosts for which they showed low herbivore success, specific diet-dependent gene clusters were identified. No diet-specific gene cluster was identified for larvae feeding on the host for which larvae showed optimal herbivore success, Z. Unique gene expression patterns, containing uniquely upregulated transcripts including specific detoxification genes, were found for larvae feeding on either B. We identified shared and unique gene expression patterns dependent of the host plant species the larvae fed on. ![]() Larvae feeding on the different host plant species showed divergent transcriptional responses. Spodoptera exigua larvae had a higher growth rate, indicator for herbivore success, when feeding on Z. The host plant species used in this study –cabbage ( Brassica oleracea), maize ( Zea mays) and tobacco ( Nicotiana tabacum)- are members of different plant families that each employ specific defence mechanisms and toxins. Here, we generated gene expression data of the generalist herbivore Spodoptera exigua (Hübner) feeding on three selected host plant species and a control (artificial diet). To understand the genetic mechanisms of insect herbivory, the transcriptional response of insects feeding on different host plant species has to be studied.
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