Epsilon Archive for Student Projects

Abstract

Insect pests feast on important crop species, which has huge economic consequences. There is always an evolutionary tug-of-war between insect pests and their plant hosts, where the insect digestive system is the first line of defence against toxins produced by the host plant in response to herbivory. This study aims at understanding the adaptation of the insect digestive system to plant toxins, such that the insights gained can be used to reduce the economic impact of these pests in crop production. Seed beetles are major agricultural pests on legumes and host adaptation is a key biological factor. Here, I used a technique to produce artificial host seeds, allowing me to manipulate precisely the amount and type of host defence compounds ingested by the larvae. This tool was applied in Callosobruchus maculatus and I assessed the effects of different food types on larval development, reproduction and survivorship. RNAseq analyses were then used to unravel the genetic mechanisms allowing the larvae to feeding on different host species. I identified 14,009 expressed genes and determined differentially expressed up and down regulated genes among all food treatments. For example, 686 and 456 genes were differentially increased in expression greater than or equal to onefold change (FDR, P < 0.05) in Black Eye Bean vs Mixed Beans and Black Eye Beans vs Bergapten, respectively. The results for the differentially expressed genes showed an enrichment of gene function relating to digestion such as cysteine proteases, P450s, small molecule binding, oxidoreductase, receptor activity and channel related molecular function. The genome wide variation in transcript regulation in digestive genes could provide additional information on how the insect adapt to environmental change. Together, this data will facilitate an understanding of the mechanisms of pest adaptation to new hosts on a molecular level as well as help to identifying genes that can be used in transgenic constructs for pest management.